Astrophysics Colloquium History
| Date |
Room |
Speaker |
Title |
May 16 2023
14:00 |
webinar
|
Alessandro Romeo
(Chalmers University of Technology)
|
The specific angular momentum of disc galaxies and its connection with galaxy morphology, bar structure and disc gravitational instability |
ABSTRACT: ABSTRACT:rnThe specific angular momenta (j=J/M) of stars (j*), gas (jgas), baryons as a whole (jb) and dark matter haloes (jh) contain clues of vital importance about how galaxies form and evolve. Using one of the largest samples of disc galaxies (S0-BCD) with high-quality rotation curves and near-infrared surface photometry, we perform a detailed comparative analysis of j that stretches across a variety of galaxy properties. Our analysis imposes tight constraints on the "retained" fractions of specific angular momentum (j*/jh, jHI/jh and jb/jh), as well as on their systematic trends with mass fraction and galaxy morphology, thus on how well specific angular momentum is conserved in the process of disc galaxy formation and evolution. In particular, one of the most innovative results of our analysis is the finding that galaxies with larger baryon fractions have also retained larger fractions of their specific angular momentum. Furthermore, our analysis demonstrates how challenging it is to characterize barred galaxies from a gravitational instability point of view. This is true not only for the popular Efstathiou, Lake & Negroponte bar instability criterion, which fails to separate barred from non-barred galaxies in about 55% of the cases, but also for the mass-weighted Toomre parameter of atomic gas, |
May 09 2023
14:00 |
room 135
|
Paolo Salucci
(sissa)
|
From Apollonian to Nietzschean: the required Paradigm Shift to successfully approach the Dark Matter Phenomenon. |
ABSTRACT: The phenomenon of the Dark matter baffles the researchers: the underlying dark particles have escaped, so far, the detection and their cosmological role appears complex and entangled with that of the Standard Model luminous particles. In this talk we discuss, for the first time, the urgent need for a change of the Paradigm which rules the search of the actual scenario underlying the DM phenomenon. In fact, there is strong evidence that the current Apollonian paradigm, that strongly favors scenarios that, under several aspects, are "beautiful", must leave the way to a Nietzschean paradigm that generates scenarios in which the "truth" can be allied with the "ugliness". |
May 02 2023
14:00 |
135
|
Carl Rodriguez
(University of North Carolina)
|
Connecting Star Cluster Formation to LIGO’s Biggest Black Holes |
ABSTRACT: Since 2015, LIGO and Virgo have detected almost 100 gravitational waves from merging black holes and neutron stars, ushering in a new era of observational astronomy. But even now, we still don’t know how these binary systems are formed in the first place! In this talk, I will describe how massive and old star clusters, such as the globular clusters in the Milky Way, are an ideal site for the production of LIGO’s binary black holes, and why we think they contribute a significant fraction of detections to date. I will then describe a project to self-consistently evolve the star cluster system of a high-resolution MHD simulation of Milky Way-mass galaxy, starting from their birth from collapsing giant molecular clouds, all the way to their destruction by galactic tidal fields, in an attempt to reproduce the globular cluster system of our own Galaxy. Finally, I will connect these results to the binary black holes detected by LIGO/Virgo, including GW190412 and GW190521, two gravitational-wave detections from the last observing run with unique masses and spins. |
Apr 18 2023
14:00 |
room 135
|
Alessandro Carones
(Università Tor Vergata Roma)
|
Prospects for blind CMB B-Modes reconstruction in future experiments |
ABSTRACT: Cosmology is now entering into the era of high-sensitivity CMB
Polarization experiments. Their main scientific target will be the
detection of primordial B-modes to definitely prove the scenario of
cosmic inflation shedding new light on the physics of the Early
Universe. However, such a signal is predicted to be much lower than the
polarized Galactic emission (foregrounds) in any region of the sky
pointing to the need for effective component separation methods. Given
our current limited knowledge of the polarized foregrounds, the
Needlet-ILC (NILC) has great relevance among all the developed
techniques, since it does not assume any specific model for their
emission. This algorithm has been successfully applied to Planck data.
In this talk, after a brief introduction to the topic, I will show how
NILC can be extended and improved so that the challenging detection of
primordial B-modes may be achieved with future ground-based and
satellite CMB experiments. |
Nov 30 2022
14:00 |
room 135
|
Elena de la Hoz
(Instituto de FÃsica de Cantabria)
|
Improvements in low-frequency foreground modeling for future primordial B-mode searches |
ABSTRACT: The detection of primordial gravitational waves would constitute compelling evidence of inflation. These waves are expected to be detectable through their imprint on the polarized CMB. However, this detection entails many experimental and data analysis challenges since it is relatively faint compared to other B-mode sources, e.g., astrophysical foregrounds, lensed E- to B-modes, and systematic errors. Optimal characterization of the foregrounds is mandatory to reach the sensitivity targeted by future CMB experiments and rule out false detections. In this talk, I present the latest improvements in the synchrotron's modeling on the Northern Hemisphere obtained using the final QUIJOTE-MFI data with data from WMAP and Planck. Moreover, I outline current efforts toward measuring the low-frequency sky (6-20 GHz) from the Southern Hemisphere with ELFS-S. |
Nov 24 2022
14:00 |
room 135
|
Elena de la Hoz
(Instituto de FÃsica de Cantabria)
|
tbd |
ABSTRACT: |
Oct 25 2022
14:00 |
room 135
|
Arminezam Amiri
(Università di Firenze)
|
A New , Multi-Cloud method to model emission lines in starforming galaxies |
ABSTRACT: Topic: A New , Multi-Cloud method to model emission lines in starforming galaxiesrnrnAbstract:rnrnThe abundances of chemical elements across cosmic epochs provide unique information on the physical processes driving the evolution of galaxies. Over the past decades many attempts have been made to measure metallicities using emission lines from photoionized gas in galaxies, ranging from direct measurements based on electron temperature and densities (Te-based metallicities), to calibration of relations between line ratios and metallicities, to the use of photoionization models. However, these methods are often based on simplifying assumption which does not adequately describe the complexity of the emitting regions, and their reliability is questioned.rnrnWe will analyze a set of galaxy spectra using our new multi component photoionization models which are able to reproduce all observed emission lines with a very high accuracy, down to a few percent. Our models thus allow for accurate metallicity measurements and to recover the well-known trends between ionization parameter and metallicity, and N/O versus Oxygen abundance. we will show that while our models do reproduce all observed line ratios, hence providing the same Te-based metallicities as observations, the true model metallicities are sometimes very different, questioning the use of Te-based metallicities. We finally present newly calibrated metallicity estimators based on ratios between strong emission lines. |
Apr 21 2022
15:30 |
135 + Webinar on Zoom
|
Giuseppe Puglisi
(Roma Tor Vergata)
|
Modeling of Galactic and extra-galactic foregrounds in the context of CMB experiments |
ABSTRACT: One of the major challenges in the context of the Cosmic Microwave Background (CMB) radiation is to detect a polarization pattern, the so called B-modes of CMB polarization, that are thought to be directly linked to the quantum tensor fluctuations produced in the Universe during the inflationary phase. To date, several challenges have prevented to detect the B-modes partly because of the lower sensitivity of the detectors and because of the contamination of our own Galaxy acting as a foreground contamination in polarization at large scales. At smaller angular scales the data are instead contaminated by the emission of extra-galactic sources like radio quasars and dusty star forming galaxies. In this talk, we show how improvements in modeling Galactic and extra-galactic foregrounds thanks to novel machine learning techniques help in correctly accounting for the foreground contamination; particularly, in the context of the future CMB experiments (e.g. SO, LiteBIRD, CMB-S4 ), where high sensitivities will be achieved at both high (~1 arcmin ) and low (~1 deg) resolutions. |
Apr 13 2021
14:00 |
Zoom webinar
|
Filippo Santoliquido
()
|
|
ABSTRACT: |
Feb 02 2021
14:00 |
Zoom webinar
|
Virginia Ajani
(CEA Paris-Saclay)
|
Investigating Cosmology and Modified Gravity models with Weak Lensing: Higher Order Statistics, Cosmological Parameter Estimation and New Analysis Methods |
ABSTRACT: Based on:
https://arxiv.org/abs/2001.10993
https://arxiv.org/abs/1908.00543 |
Dec 23 2020
10:00 |
Remotely via zoom, link below
|
Sabyasachi GOSWAMI
(SISSA, Trieste, Italy)
|
On the effects of the Initial Mass Function on galactic chemical enrichment: the role of Pair Instability Superonovae |
ABSTRACT: Zoom link to join:
https://sissa-it.zoom.us/j/82407213175?pwd=M3hLQUJ1MHpjdzZGVHlpS2tHd1lQQT09 |
Dec 10 2020
15:00 |
Remotely via zoom, link below
|
Farida FARSIAN
(SISSA, Trieste, Italy)
|
Foreground Challenge to CMB Polarization: Present Methodologies and New Concepts |
ABSTRACT: Zoom link to join:
https://sissa-it.zoom.us/j/83595206871?pwd=bHJPTUptemlHekRMczNra3dJWWtjdz09) |
Nov 24 2020
14:00 |
Remotely via zoom, link below
|
Suvodip MUKHERJEE
(University of Amsterdam)
|
New Frontiers in Cosmology using Multi-Messenger Observations |
ABSTRACT: The discovery of astrophysical gravitational waves has opened
a new avenue to explore the cosmos using transients. I will discuss a
few new frontiers in the field of physical cosmology and fundamental
physics that can be explored using gravitational waves from the ongoing
gravitational wave detectors and in the future from gravitational wave
detectors such as LISA, Einstein Telescope, and Cosmic Explorer. I will
elucidate the existence of synergies between the electromagnetic signals
and gravitational wave signals and its importance in understanding the
standard model of cosmology and unveiling new physics.
---
Zoom link to join
https://sissa-it.zoom.us/j/84847391999?pwd=WFBiaEQ3R1RpT2JKOXRETTQ3SENrdz09 |
Nov 17 2020
15:00 |
Remotely via zoom, link below abstract
|
Fabio PACUCCI
(Harvard University)
|
Detecting the Dawn of Black Holes |
ABSTRACT: In this talk I discuss the quest to unravel two undetected
populations of high-z black holes. The first population of black holes
formed when the Universe was younger than 500 Myr, while by z=7 we have
observations of fully-fledged, shining quasars. Shedding light on this
cosmic period is one of the key tasks that the astronomical community
will focus on in the next decade. The observational signatures of black
hole seeds remain largely unexplored, and we are yet to detect these
sources. I present detailed predictions for the spectra of different
categories of seeds, and a photometric method to identify them in
surveys. I explore the role that future facilities (e.g., JWST, Athena,
Lynx, AXIS, LISA) will play in this quest, by detecting both black hole
accretion and mergers. Furthermore, I show a detailed analysis of the
requirements and the expectations for a comprehensive search of z > 10
black hole seeds. Moving at slightly lower redshifts, the discovery of
the first strongly lensed quasar at z > 6 (J0439+1634) represents a
breakthrough in our understanding of the early Universe. We recently
predicted that the observed population of z > 6 quasars should contain
many mildly magnified sources, with image separations below the
resolution threshold. Additionally, current selection criteria should
have missed a substantial population of lensed z > 6 quasars. I estimate
the fraction of undetected quasars as a function of the slope of the
bright end of the quasar luminosity function. For steep values of this
parameter, the vast majority of the z > 6 quasar population is lensed
and still undetected. These "phantom quasars" would be misclassified and
mixed up with low-z galaxies.
---
Zoom link to join
https://sissa-it.zoom.us/j/86306912096?pwd=TTV6aU1iVVYxSEZBVk4rM0ZFSXFjdz09 |
Mar 16 2020
14:00 |
FULLY REMOTE PH.D. DEFENCE [public zoom link: EXPIRED]
|
Chiara DI PAOLO
(SISSA, Trieste, Italy)
|
Fundamental Properties of the Dark and the Luminous Matter from Low Surface Brightness Discs |
ABSTRACT: Dark matter (DM) is one of the biggest mystery in the Universe. After a brief discussion of the past DM evidences and the main proposed candidates and scenarios for the DM phenomenon, I will focus on rotating disc galaxies giving a special attention to the Low Surface Brightness (LSB) galaxies. The main observational properties related to the baryonic matter in LSBs, analysed over the last decades, will be briefly recalled. Next, I will show the main results that I obtained by means of the mass modelling of the LSBs rotation curves (URC analysis). Finally, the results will be compared to those of different kinds of galaxies and contextualised in the large DM phenomenon. |
Feb 18 2020
14:00 |
room 135
|
Dominik Schwarz
(Uni Bielefeld)
|
Unravelling the largest cosmic scales by means of the SKA-MPG telescope |
ABSTRACT: |
Feb 04 2020
14:00 |
room 135
|
Alberto Masini
(SISSA)
|
AGN obscuration across the cosmic history |
ABSTRACT: |
Jan 21 2020
14:00 |
135
|
Luca Pagano
(Universita\' Ferrara)
|
Planck likelihood 2018 |
ABSTRACT: |
Jan 14 2020
14:00 |
room 135
|
Alireza Vafaei Sadr
()
|
seminar on machine learning |
ABSTRACT: |
Dec 10 2019
16:30 |
room 135
|
Michele Punturo
(INFN)
|
|
ABSTRACT: |
Nov 13 2019
16:30 |
135
|
Rajsekhar Mohapatra
()
|
Role of turbulence, cooling and stratification in galaxy cluster cores |
ABSTRACT: The Active galactic Nuclei feedback model is an attractive solution to the
cooling flow problem in the intracluster medium (ICM). However, the exact
mechanism by which AGN jets transfer energy to the ICM is unclear. Recently,
a lot of attention has been paid to the role of turbulent heating in
arresting the cooling of the ICM gas.Â
AGN jets and the motion of galaxies and haloes through the intracluster
medium can drive turbulence in the ICM. When this turbulence dissipates at
viscous scales, it is supposed to heat up the ICM gas and prevent runaway
cooling of the ICM gas.
In our work, we study the impact of turbulence driving length scale, the
level of turbulence heating and the strength of background stratification on
the different statistical properties of ICM gas. We perform high resolution
hydrodynamic simulations of homogeneous isotropic turbulence and stratified
turbulence. We include radiative cooling and global thermal balance in some
of our simulations. We derive the scaling relations between density and
pressure fluctuations, rms Mach number and the strength of background
stratification (Richardson number) and compare our results to recent
observations. From our homogeneous isotropic simulations, we get an upper
bound of <= 10 % on the level of turbulence heating in the ICM. |
Nov 05 2019
16:30 |
|
Roberto De Carli
(INAF)
|
The interstellar medium at high redshift |
ABSTRACT: The gaseous content of galaxies is one of the key ingredients of galaxy
evolution: It fuels star formation and nuclear activity, and at the same
time it is the main receiver of any feedback mechanism from these two
processes. However, we have only very limited knowledge of the gas content
and of its physical properties in galaxies beyond the local universe. As a
result, no description of galaxy formation can be fully validated without a
better understanding of 1) how much gas was available for star formation in
different cosmic times; 2) how the star formation efficiency, i.e., the
capability of a galaxy to form stars from a given amount of gas, evolve
through cosmic history, and which are physical conditions that governed this
evolution; 3) what was the interplay between the interstellar medium, star
formation, and nuclear activity. These questions are particularly critical
at the very high redshifts (z>6, when the universe was <1 Gyr old), where
our census of galaxies is highly incomplete, especially at the high-mass
end, and galaxies followed very different evolution according to the mass of
their initial gas reservoir. In this talk I will present the results of
various observational campaigns aimed at addressing these questions, in
particular by capitalizing on the unprecedented capabilities offered by the
Atacama Large Millimeter Array and the Northern Extended Millimeter Array.
These findings will guide the next generation of simulations and theoretical
models, thus marking a transformational step in our understanding of galaxy
evolution. |
Oct 29 2019
16:15 |
room 128-129
|
Martyna Chruslinska
(Radboud University)
|
Metallicity of stars throughout the cosmic history (and the gravitational waves observations) |
ABSTRACT: Metallicity is one of the crucial factors that determine stellar and binary
evolution.
To characterize the properties of stellar populations one needs to know
the fraction of stars forming at different metallicities.
Knowing how this fraction evolves over the cosmic history is necessary e.g.
to estimate the rates of occurrence of any stellar or binary evolution
related phenomena
(e.g. different types of supernovae, double compact object mergers or gamma
ray bursts).
Such theoretical rate estimates can be for instance confronted with
observational limits to validate
the assumptions about the evolution of the progenitor star or system leading
to a certain transient.
However, to perform the comparison correctly one needs to know the
uncertainties related to
all of the 'ingredients' used in the calculations, in particular
to the assumed star formation history and chemical evolution of the
Universe.
This is especially important in the case of transients whose formation
scenarios
are particularly sensitive to metallicity, e.g. long gamma ray bursts and
double black hole mergers.
Different approaches have been taken in the literature to learn about the
distribution of
the cosmic star formation rate over metallicities and redshifts.
The aim of my recent study was to find the observational-based distribution
and constrain its uncertainty.
To achieve this, I combined the observational scaling relations from
various observational studies describing the properties of star forming
galaxies
(star formation rate, mass, metallicity).
I will discuss the uncertainty of the obtained distribution due to the
currently unresolved problems
in the determination of various characteristics of galaxies and
the scaling relations, such as the absolute metallicity scale or the
flattening in the star formation mass relation. I will put those results in
context of the gravitational waves observations. |
Oct 17 2019
11:00 |
room 004
|
Barbara Padricielli
(VIRGO collaboration)
|
Gravitational waves and multi-messenger astronomy: a new window on the Universe |
ABSTRACT: |
Oct 15 2019
16:30 |
room 135
|
Mark Vogelsberger
(MIT, Boston)
|
Simulating Galaxy Formation: Illustris, IllustrisTNG and beyond |
ABSTRACT: Cosmological simulations of galaxy formation have evolved significantly over\r\nthe last years.\r\nIn my talk I will describe recent efforts to model the large-scale\r\ndistribution\r\nof galaxies with cosmological hydrodynamics simulations. I will focus on the\r\nIllustris simulation, and our new simulation campaign, the IllustrisTNG\r\nproject. After demonstrating the success of these simulations in terms of\r\nreproducing an enormous amount of observational data, I will also talk about\r\ntheir limitations and directions for further improvements over the next\r\ncouple\r\nof years. |
Oct 09 2019
14:00 |
|
Kasia Malek
(NCBJ institute, Poland)
|
|
ABSTRACT: |
Oct 08 2019
14:00 |
135
|
Claudio Gheller
()
|
|
ABSTRACT: |
Oct 01 2019
14:00 |
room 135
|
Roberto De Carli
(INAF)
|
|
ABSTRACT: |
Sep 17 2019
14:00 |
room 135
|
Pratika Dayal
(Kapteyn Astronomical Institute, University of Groningen)
|
Early galaxy formation and its large-scale effects |
ABSTRACT: |
Sep 03 2019
14:00 |
Room 135
|
Chris Harrison
(ESO, Garching, Munich)
|
Feedback from luminous AGN and quasars across cosmic time |
ABSTRACT: TBDTBD |
Jul 29 2019
14:00 |
room 135
|
Max Silva
(University of California , San Diego)
|
Modern Detector and Readout Technologies Enabling Large Arrays for CMB Telescopes |
ABSTRACT: Current CMB experiments have detectors which are shot noise dominated such that we can only achieve lower noise CMB maps by adding more detector years of data to average over. To successfully field larger numbers of detectors, significant effort has gone into scaling the size of cryogenic receivers, optics, and the multiplexed readout technology. My PhD thesis work focuses largely on the novel detector and readout technologies under development, but I will also show work from colleagues on cryogenic receiver design, and innovations in cryogenic mm-wave optics. This will serve as a broad overview of some of the enabling technologies that have been developed or are under development for next-generation projects such CMB-S4 and Simons Observatory. |
Jun 18 2019
14:00 |
room 135
|
Claudio Gheller
(Zurich University)
|
|
ABSTRACT: |
Sep 17 2018
14:00 |
room 135
|
Marco Raveri
()
|
tba |
ABSTRACT: tba |
Jul 03 2018
14:00 |
|
Bikash Ranjan Dinda
(Centre for Theoretical Physics, Jamia Millia Islamia, New Delhi, India)
|
Signature of dark energy in galaxy power spectrum on the large cosmological scale and in the weak lensing statistics |
ABSTRACT: The late-time cosmic acceleration can be explained by dark energy or byrnmodified theories of gravity. The presence of dark energy not only affects the background evolution of the Universe but also plays a crucial role inrnthe structure formation history. Due to the negative pressure, the darkrnenergy slows down the growth of structures. The Cosmological Constant asrndark energy has no perturbation at any scales. But any other evolving dark energy has perturbation. The presence of perturbations is negligible on smaller scales but has a non-negligible contribution on larger scales whichrncan be seen through cosmological observables like galaxy power spectrum.rnThis effect can distinguish the different dark energy models morernsignificantly on larger scales compared to the LCDM model. Weak lensingrnstatistics like convergence power spectrum and bispectrum can also play a significant role in the structure formation.rnWe explore detectability of the different dark energy models usingrnlarge-scale galaxy power spectra as well as weak lensing convergence power spectrum and bispectrum. |
May 09 2017
14:00 |
Room 135
|
Stefano Ettori
(Osservatorio Astronomico di Bologna)
|
X-ray, Sunyeav-Zeldovich signal and dark matter in galaxy clusters |
ABSTRACT: The key tool to use galaxy clusters as astrophysical laboratories and\r\ncosmological probes is the knowledge of the distribution of the their\r\ngravitating and baryonic mass. I\'ll discuss the current status in reconstructing the profiles of the gas\r\nmass, the total mass and other thermodynamical properties from observations\r\nvia X-rays and the Sunyeav-Zeldovich effect, highlighting the present\r\nlimitations and biases, in particular in the clusters\' outskirts and at\r\nhigh-redshift, where we have obtained the first constraint on the\r\nconcentration-mass relation at z>0.7 from X-ray analysis. I\'ll show how the\r\nuse of generalized scaling relations can help to reduce the scatter in\r\nobtaining the total mass and to constrain the physics responsible for the\r\nobserved deviations from the self-similar model. I\'ll elucidate how Athena,\r\nthe next-generation X-ray observatory and ESA-L2 mission, will address these\r\nissues. |
May 02 2017
14:00 |
Room 135
|
Andrea Contin and Nicolo' Masi
((University of Bologna, Director of Interdipartmental Center for Research on Environmental Sciences) (Dipartimento di Fisica, Universita' di Bologna))
|
The AMS experiment latest results and interpretation |
ABSTRACT: |
May 10 2016
14:00 |
SISSA main building
|
Alessandro Pizzella
(Padua University)
|
The origin of large-scale counter-rotating stellar disks in galaxies |
ABSTRACT: Large-scale stellar disks that rotate in opposite directions\r\n are observed in several galaxies. The ages of the two stellar\r\n counter-rotating components are the key elements to understand\r\n formation scenarios: internal origin, {em in situ} formation from\r\n an acquired gas cloud, and binary galaxy merger. The results obtained\r\n with VIMOS and MUSE seem to demonstrate the external origin of such\r\n structures. |
May 03 2016
14:00 |
SISSA main building, room 135
|
Veronique Buat
()
|
Dust attenuation in the Universe: what do we know about its variation with redshift and from galaxy to galaxy? |
ABSTRACT: In this talk I will present global measurements of dust attenuation in the Ununiverse based on an enery budget bewteen the UV (stars) and the IR (dust)rnlight. I will discuss the differences found between galaxy populationsrnselected either in UV or in IR and show that introducing the stellar massrncan reconcile the different measurements and the evolution of dustrnobscuration with redshift.rnWhereas we get a consistent picture of the average obscuration in galaxies,rnthe definition of a universal attenuation curve is very questionable andrnmore than 20 years after the first attenuation law for local starburstrngalaxies proposed by Calzetti and collaborators, we are still answering thernapplicability of this law to different galaxy populations in the nearby andrnin the high redshift universe. I will review the recent advances on thernderivation of attenuation curves in different surveys, and the implicationrnof the adopted law on the derivation of fundamental parameters like starrnformation rates and stellar masses. In particular I will present our veryrnrecent results obtain with the HELP/Herschel team. |
Mar 01 2016
14:00 |
room 135
|
Alfonso Veropalumbo
(Universita\' di Bologna)
|
Cosmological constraints from the clustering of galaxy clusters |
ABSTRACT: Galaxy clusters play a leading role in both present and planned\r\ncosmological investigations.\r\nThey represent the biggest collapsed structure of the Universe, sitting on top of the highest peaks of the dark matter density field. The possibility of modelling their statistical properties as a\r\nfunction of cosmological parameters, combined with the capability of\r\nmeasuring their basic properties, such as the mass, with relative simplicity with respect to other astrophysical objects, makes them optimal tracers of the large scale structure of the Universe. In this talk I will show precise estimates of the clustering for these objects in three different redshift bins, focusing in particular on the detectability of the baryon acoustic oscillation (BAO).\r\nWe detect the peak of baryon acoustic oscillations for all the three samples with high significance, despite the paucity of the samples.\r\nCombining these measurements, robust observational constraints on the\r\ndistance-redshift relation are obtained.\r\nThis is the first time the distance-redshift relation has been constrained using only the peak of baryon acoustic oscillations of galaxy clusters. |
Nov 26 2015
16:00 |
135
|
Simone Aiola
(University of Pittsburgh)
|
New Probes of Large-scale CMB Anomalies |
ABSTRACT: Inflation prescribes a homogenous and isotropic universe on largernscales, and it generates density fluctuations which are expected to be spatially correlated over the whole Hubble volume. Such fundamental predictions have been tested with current Cosmic Microwave Background (CMB) data and found to be inrntension with our — remarkably simple — ΛCDM model. Is it just arnrandom fluke or a fundamental issue with the present model? In thisrntalk, I will present new possibilities of using the CMB polarizationrnas a probe of the measured suppression of the large-scale temperature rncorrelation function. I will also discuss the viability of usingrnthis new technique with present and upcoming data. rnTo further analyze the statistical properties of the CMB temperaturernsky, I will show results from our latest analysisfocused onrnconstraining the degree of statistical anisotropy of the CMB in therncontext of the observed large-scale dipole power asymmetry. I willalso highlight future prospects for improving the current analysis. rnTo conclude, I will celebrate the success of the current model, asrnconstrained by the small-scale CMB fluctuations, by giving a briefrndescription of the Atacama Cosmology Telescope map-making pipelinernand related science. |
Nov 20 2015
11:30 |
Room 128
|
Julian Borrill
(Lawrence Berkeley National Laboratory)
|
High Performance Computing for Cosmic Microwave Background Experiments |
ABSTRACT: |
Sep 30 2015
0:00 |
library blue meeting room
|
Obi I. Anthony
(SISSA)
|
Type IIb Supernova 2013df Entering Into An Interaction Phase: A Link between the Progenitor and the Mass Loss |
ABSTRACT: We report the late-time evolution of Type IIb Supernova (SN IIb) 2013df. SN 2013df showed a dramatic change in its spectral features at ~1 year after the explosion. Early on it showed typical characteristics shared by SNe IIb/Ib/Ic dominated by metal emission lines, while later on it was dominated by broad and flat-topped Halpha and He I emissions. The late-time spectra are strikingly similar to SN IIb 1993J, which is the only previous example clearly showing the same transition. This late-time evolution is fully explained by a change in the energy input from the 56Co decay to the interaction between the SN ejecta and dense circumstellar matter (CSM). The mass loss rate is derived to be ~(5.4 +- 3.2) x 10^{-5} Msun/yr (for the wind velocity of ~20 km/s), similar to SN 1993J but larger than SN IIb 2011dh by an order of magnitude. The striking similarity between SNe 2013df and 1993J in the (candidate) progenitors and the CSM environments, and the contrast in these natures to SN 2011dh, infer that there is a link between the natures of the progenitor and the mass loss: SNe IIb with a more extended progenitor have experienced a much stronger mass loss in the final centuries toward the explosion. It might indicate that SNe IIb from a more extended progenitor are the explosions during a strong binary interaction phase, while those from a less extended progenitor have a delay between the strong binary interaction and the explosion. |
Jul 01 2015
14:00 |
SISSA, Room 135
|
Yoel Rephaeli
(Tel Aviv University)
|
Galactic Energetic Particles and Their Radiative Yields in Clusters |
ABSTRACT: Tba |
Jun 23 2015
14:00 |
SISSA, Room 135
|
Michal Chodorowski
(Nicolaus Coperincus Astronomical Center, Warsaw,)
|
Distortions of galaxy clustering in redshift surveys |
ABSTRACT: In deep three-dimensional surveys of galaxies, as the third coordinate of a galaxy's position in space its redshift is adopted. Density inhomogeneities in the Universe induce deviations from the simple Hubble velocity flow of galaxies. As a result, redshift is not a perfect estimator of the true distance and maps of the galaxy distribution in REDSHIFT SPACE give a distorted view of their spatial distribution in real (configuration) space. In particular, the two-point (auto-)correlation function of galaxies is anisotropic in redshift space. Interestingly, the amount of anisotropy dependsrnon the rate of growth of density fluctuations in the Universe, which is different in dark energy and modified gravity cosmologies. A measurement of the growth rate from galaxy redshift surveys can thus serve as a method to discriminate between different competing cosmological theories, explaining the current acceleration of the Universe expansion in a qualitativelyrn distinct way.rnTo achieve this goal, very precise estimates of the growth rate from observations, as well as accurate theoretical models of the correlation function of galaxies in redshift space are needed. Quality of the data in spectroscopic galaxy surveys steadily increases in time. However, despite of numerous attempts over the last two decades, there is still no model which satisfactorily predicts isocontours of the correlation function in redshift space. After describing a few most popular models existing in the literature, I will briefly present my recent work on the subject. My model has more realistic physical assumptions than the former and in consequence fares muchrn better when compared to the results of N-body simulations. |
Jun 10 2015
2:00 |
big meeting room 7th floor
|
Ekaterina Karukes
(SISSA)
|
The Variation of Rotation Curve Shapes as a Signature of the Effects of Baryons on Dark Matter Density Profiles |
ABSTRACT: Rotation curves of galaxies show a wide range of shapes, which can be paramaterized as scatter in Vrot(1kpc)/Vmax i.e.the ratio of the rotation velocity measured at 1kpc and the maximum measured rotation velocity. We examine whether the observed scatter can be accounted for by combining scatters in disc scale-lengths, the concentration-halo mass relation, and the Mstar-Mhalo relation. We use these scatters to create model galaxy populations; when housed within dark matter halos that have universal, NFW density profiles, the model does not match the lowest observed values of Vrot(1kpc)/Vmax and has too little scatter in Vrot(1kpc)/Vmax compared to observations. By contrast, a model using a mass dependant dark matter profile, where the inner slope is determined by the ratio of Mstar/Mhalo, produces galaxies with low values of Vrot(1kpc)/Vmax and a much larger scatter, both in agreement with observation. We conclude that the large observed scatter in Vrot(1kpc)/Vmax favours density profiles that are significantly affected by baryonic processes. Alternative dark matter core formation models are also disfavoured by the large scatter in Vrot(1kpc)/Vmax, implying that baryonic physics would be required to affect density profiles in such models, which defeats a large part of their motivation without ruling them out. |
May 20 2015
0:00 |
big meeting room 7th floor
|
Claudia Mancuso
(SISSA)
|
The dust mass in z > 6 normal star forming galaxies |
ABSTRACT: We interpret recent ALMA observations of z > 6 normal star forming galaxies by means of a semi-numerical method, which couples the output of a cosmological hydrodynamical simulation with a chemical evolution model which accounts for the contribution to dust enrichment from supernovae, asymptotic giant branch stars and grain growth in the interstellar medium. We find that while stellar sources dominate the dust mass of small galaxies, the higher level of metal enrichment experienced by galaxies with Mstar > 10^9 Msun allows efficient grain growth, which provides the dominant contribution to the dust mass. Even assuming maximally efficient supernova dust production, the observed dust mass of the z = 7.5 galaxy A1689-zD1 requires very efficient grain growth. This, in turn, implies that in this galaxy the average density of the cold and dense gas, where grain growth occurs, is comparable to that inferred from observations of QSO host galaxies at similar redshifts. Although plausible, the upper limits on the dust continuum emission of galaxies at 6.5 < z < 7.5 show that these conditions must not apply to the bulk of the high redshift galaxy population |
May 05 2015
15:00 |
SISSA, Room 135
|
Marco Bruni
(Porthsmouth University)
|
The non-linear post-Friedmann framework and Einstein's signature in large-scale structure |
ABSTRACT: Non-linear structure formation at scales much smaller than the Hubble horizon is traditionally studied with Newtonian methods, for
instance N-body simulations, while early Universe and horizon scales
perturbations are investigated with relativistic perturbation theory.
In view of new large scale galaxy surveys that will provide data with
an unprecedented accuracy, it is timely to bridge the gap between
these different approaches, going beyond the Newtonian approximation
and unifying the study of the very large scales and the non-linear
scales in a single theoretical framework.
In this talk I will describe the post-Friedmann framework, a sort of
post-Minkowskian (weak field) approach to cosmology, such that at
leading order in a 1/c expansion Newtonian cosmology is recovered as a
consistent approximate solution of Einstein equations, on top of a
Friedmannian background. In this framework, linear and non-linear
relativistic contributions appear at next order. Resumming variables
and linearising the equations one recovers first-order relativistic
perturbation theory, i.e. the framework is valid on horizon scales and
beyond.
I will illustrate the first practical application, i.e. the extraction
of the frame-dragging gravitomagnetic potential from N-body
simulations, and its power spectrum. Similarly, the difference
between the two scalar potential, known as "slip" in cosmology, can
also in principle be computed, sourced at leading order by purely
Newtonian non-linear terms. I will also present relativistic
non-Gaussian corrections to the initial conditions in Newtonian
simulations that arise at second order in perturbation theory. |
Apr 22 2015
2:00 |
library blue meeting room
|
Serena Perrotta
(SISSA)
|
Evidence for feedback in action from the molecular gas content in the z~1.6 outflowing QSO XID2028 |
ABSTRACT: Gas outflows are believed to play a pivotal role in shaping galaxies, as they regulate both star formation and black hole growth. Despite their ubiquitous presence, the origin and the acceleration mechanism of such powerful and extended winds is not yet understood. Direct observations of the cold gas component in objects with detected outflows at other wavelengths are needed to assess the impact of the outflow on the host galaxy interstellar medium (ISM). We observed with the Plateau de Bure Interferometer an obscured quasar at z~1.5, XID2028, for which the presence of an ionised outflow has been unambiguously signalled by NIR spectroscopy. The detection of CO(3-2) emission in this source allows us to infer the molecular gas content and compare it to the ISM mass derived from the dust emission. We then analyze the results in the context of recent insights on scaling relations, which describe the gas content of the overall population of star-forming galaxies at a similar redshifts. The Star formation efficiency (~100) and gas mass (M_gas=2.1-9.5x10^{10} M_sun) inferred from the CO(3-2) line depend on the underlying assumptions on the excitation of the transition and the CO-to-H2 conversion factor. However, the combination of this information and the ISM mass estimated from the dust mass suggests that the ISM/gas content of XID2028 is significantly lower than expected for its observed M⋆, sSFR and redshift, based on the most up-to-date calibrations (with gas fraction <20% and depletion time scale <340 Myr). Overall, the constraints we obtain from the far infrared and millimeter data suggest that we are observing QSO feedback able to remove the gas from the host |
Apr 15 2015
2:00 |
big meeting room 7th floor
|
Jing Tang
(SISSA)
|
Old supernova dust factory revealed at the Galactic center |
ABSTRACT: Dust formation in supernova ejecta is currently the leading candidate to explain the large quantities of dust observed in the distant, early Universe. However, it is unclear whether the ejecta-formed dust can survive the hot interior of the supernova remnant (SNR). We present infrared observations of ~0.02 M⊙ of warm (~100 K) dust seen near the center of the ~10,000 yr-old Sgr A East SNR at the Galactic center. Our findings signify the detection of dust within an older SNR that is expanding into a relatively dense surrounding medium (ne ~ 100 cm−3) and has survived the passage of the reverse shock. The results suggest that supernovae may indeed be the dominant dust production mechanism in the dense environment of early Universe galaxies. |
Feb 26 2015
15:00 |
SISSA, Room 128/129
|
Andrea Lapi
(University of "Tor Vergata" (Rome) - SISSA)
|
High-z Galaxies at the Interface between Astrophysics and Cosmology |
ABSTRACT: Thanks to the Herschel and Planck satellites, recent major advancesrnhave recently occurred both in astrophysics and cosmology,rnand times are mature for setting up a close cross-talk between theserndisciplines. Detailed knowledge of the cosmological backgroundrnis required to provide a sensible framework for galaxy formation,rnwhile accurate astrophysical understanding of galaxy and cluster formationrnis essential to keep biases under control in precision cosmological studies.rnI will show how joint astrophysical and cosmological constraints (includingrnthe nature of dark matter and dark energy, the epoch of reionization, neutrino physics, tests of gravity theory, etc.) can be derived from state-of-the-art techniques related to weak and strong galaxy-scale gravitational lensing, galaxy-CMB lensing cross-correlation, and tomographical studies of the galaxy clustering signal.rnThis will be particularly relevant especially in the light of new orrnupcoming astrophysically-oriented facilities like ALMA, JWST, SKA, and cosmological experiments like EUCLID, LSST, DES. |
Feb 17 2015
14:00 |
SISSA, Room 135
|
Anna Bonaldi
(Manchester University)
|
Cosmology with Planck Sunyaev-Zeldovich cluster counts |
ABSTRACT: I present the recent results from Planck on Cosmology with Sunyaev-Zeldovich (SZ) cluster counts. In the paper, released 5 Feb, we present cluster counts and corresponding cosmological constraints from the Planck full mission data set. Our catalogue consists of
439 clusters detected via their SZ signal down to a signal-to-noise of six, and is more than a factor of two larger than the 2013 Planck cluster cosmology sample. The counts are consistent with those from 2013 and yield compatible constraints under the same modelling assumptions. Taking advantage of the larger catalogue, we extend our analysis to the
two-dimensional distribution in redshift and signal-to-noise. We use mass estimates from two recent studies of gravitational lensing of background galaxies by Planck clusters to provide priors on the hydrostatic bias parameter, 1 − b. In addition, we use lensing of cosmic microwave background (CMB) temperature fluctuations by Planck clusters as a third independent constraint on this parameter. These various calibrations imply constraints on the present-day amplitude of matter fluctuations in varying degrees of tension with those coming from Planck analysis of primary fluctuations in the CMB; for the lowest estimated values of 1 − b the tension is mild, only a little over one standard deviation, while for the largest estimated value it remains substantial. We also examine constraints on extensions to the base flat ΛCDM model by combining the cluster and CMB constraints. The combination appears to favour non-minimal neutrino masses, but this possibility does little to relieve the overall tension because it simultaneously lowers the implied value of the Hubble parameter, thereby exacerbating the discrepancy with most current astrophysical estimates. Improving the precision of cluster mass calibrations from the current 10%-level to 1% would significantly strengthen these combined analyses and provide a stringent test of the base ΛCDM model. |
Feb 03 2015
14:00 |
SISSA, Room 135
|
Isabella Prandoni
(Istituto Radioastronomia, Bologna)
|
Mapping the Universe with the Square Kilometre Array |
ABSTRACT: The Square-Kilometer Array (SKA) is an integral part of the next-generation observatories that will survey the Universe across the electromagnetic spectrum, and beyond, revolutionizing our view of Fundamental Physics, Astrophysics and Cosmology.
In the present talk I will describe the SKA project, its timeline and main scientific scopes, focussing on the preparatory work which is leading to the so-called SKA Phase 1.
The involvement of the Italian community will be also highlighted. |
Dec 09 2014
14:00 |
SISSA, Room 135
|
Kam Arnold
(UCSD, University of California)
|
Cosmic Microwave Background Polarization: Measurements with POLARBEAR and Future Scientific Prospects |
ABSTRACT: It is an exciting time in cosmic microwave background (CMB) polarization
research. A little less than one year ago, POLARBEAR announced its
measurement of the gravitational lensing deflection power spectrum using CMB polarization alone. This demonstrated a technique that can be used as a way to measure all of the gravitational structure in the observable universe, giving insight into the early action of dark energy and the sum of the neutrino masses. In 2014, the POLARBEAR team published this result along with our measurement of a non-zero B-mode polarization angular power spectrum, probing polarization at sub-degree scales. Also in 2014, BICEP2 published observations from the south pole of B-mode polarization at degree scales, consistent with the prediction of cosmic inflation. A precision characterization of this inflationary signal would shed light on physics at energy scales of 10^16 GeV, ten orders of magnitude higher than energies at the Large Hadron Collider, where the strong and electroweak forces are expected to unify. But it is unclear weather the signal BICEP2 measured is from cosmic or galactic sources, something the Planck team is weighing in on - along with many other cosmological topics - with their polarization data release this month. Going forward, extracting all of the exciting science possible from CMB polarization will require more precise observations over a large fraction of the sky with angular resolution of a few arcminutes,observations that POLARBEAR and our multi-chroic expansion- the Simons Array - are well-positioned to carry out. |
Dec 02 2014
14:00 |
SISSA, Room 135
|
Pierstefano Corasaniti
(CNRS & Observatoire de Paris)
|
Imprints of Dark Energy on the non-Linear Cosmic Structure Formation |
ABSTRACT: The next generation of cosmological probes will test the nature of dark
energy in the universe through observations of the distribution of cosmic structures at small scales and in large cosmic volumes. In this talk I will review the imprints of dark energy on the non-linear structure formation as inferred from N-body simulation studies. These suggest that dark energy may have a more important impact on the complex processes that shape the formation and evolution of cosmic structures. |
Nov 18 2014
16:00 |
Tba
|
Michele Cappellari
()
|
Tba |
ABSTRACT: Tba |
Nov 04 2014
14:00 |
SISSA, Room 135
|
Franco Vazza
(University of Hamburg)
|
The magnetism in the cosmic web from simulations and looking towards future observations. |
ABSTRACT: Magnetic fields are nowadays routinely observed in galaxies and galaxy clusters, while little is known about their distribution in cosmic filaments and for most of the cosmic web. However, the latter potentially carries information about the origin of cosmic magnetism, as it should relate with early cosmological epochs. I will show what can be presently done to follow the growth of magnetic fields in the cosmic web using cosmological simulations, and discuss how this can be used to study the detectability of the cosmic web with future (or incoming) radio facilities, as well as to study the propagation of ultra high-energy cosmic rays in the Universe. |
Oct 28 2014
14:00 |
SISSA, Room 135
|
Nicola Turini
(University of Siena)
|
Missing Mass searching with the Totem and CMS detectors at LHC |
ABSTRACT: The Totem experiment is placed in the interaction point 5 of the LHC ring as the CMS experiment. It covers the large pseudorapidy angles and complements the CMS acceptance for the forward physics. 26 detectors are placed at 210m-220m from the interaction point on both arms. They are inserted in special retractable pots (Roman Pots) to detect elastically and inelastically scattered protons, while inelastic trackers are placed up to pseudorapidity 6.5 in the forward region of the CMS detector.\r\nI will describe a method we developed to detect invisible particles that may emerge in central diffractive proton interactions. In this process, that involve gluon-gluon fusion or gamma-gamma interactions, the interacting protonsare surviving. The precision spectrometer made by the combination of Roman Pots detectors and machine magnets measures the production parameters. The disappearance of mass is detected by the difference of invariant mass produced, measured by the protons, and the particle flow measurement in the CMS central region. |
Oct 14 2014
14:00 |
room 135
|
Eloisa Menegoni
(Observatoire de Paris)
|
Constraints on dark energy models with CMB data |
ABSTRACT: In this talk I will discuss present and future cosmological constraints on variations of the fine structure constant induced by an early dark energy component having the simplest allowed (linear) coupling to electro-magnetism. The current cosmological data show no variation of the fine structure constant at recombination with respect to the present-day value. Moreover, I will consider constraints on the parameter quantifying the strength of the coupling by the scalar field. However forthcoming or future missions, such as the Planck Surveyor and the CMBPol satellite, can match and possibly even surpass the sensitivity of current local tests. Finally, I will discuss the effects of a dark energy equation of state parameter varying with redshift on the CMB anisotropies. |
May 13 2014
14:00 |
|
David Mota
(Institute for Theoretical Astrophysics, Oslo)
|
tba |
ABSTRACT: |
Apr 08 2014
14:00 |
tba
|
Manolis Papastergis
(Kapteyn Institute/University of Groningen)
|
Galaxy formation and small-scale cosmology with the ALFALFA 21cm survey |
ABSTRACT: The ALFALFA survey is a blind survey in the 21cm line of atomic
hydrogen (HI), performed with the Arecibo radiotelescope. The
statistical analysis of the survey's dataset, which represents
the largest HI selected sample Dto date, allows us to address
key open questions in galaxy formation and small-scale cosmology. First, we show that low-mass halos are severely "baryon depleted",
in the sense that their combined stellar and atomic gas mass on
average accounts for only a few percent of the cosmic baryon fraction.
If baryon depletion is to be explained by supernova feedback,
the implied mass loading factors are enormous.
It is not yet clear whether such efficient feedback is realistic,
and whether it can be reconciled with observations. Moreover, we
use the distribution of galactic rotational velocities measured
by ALFALFA to infer statistically the host halo mass of ALFALFA galaxies
in a Lambda_CDM cosmology. We show that for extreme dwarf
galaxies the host halo masses predicted in Lambda_CDM are too
large to be compatible with the internal kinematics of
these objects. We argue that this is the field analog of the
"too big to fail" problem found for Milky Way satellites, and we
elaborate on the implications regarding the properties of dark matter
on small scales. |
Mar 25 2014
14:00 |
SISSA, Room 005
|
Francesco Sylos Labini
(Centro Studi e Ricerche Enrico Fermi; Istituto dei Sistemi Complessi CNR)
|
Violent and mild relaxation of an isolated self-gravitating uniform and spherical cloud of particle |
ABSTRACT: The gravitational relaxation process acting during the collapse of a
self-gravitating and isolated cloud of particles is the fundamental
physical mechanism underlying the formation of virialized structures
both in astrophysical and cosmological contexts. These structures,
although never reach thermodynamical equilibrium, represent long-lived
states whose lifetime diverge with the number of system particles. . The
understanding of the relaxation process should eventually explain the
density profiles observed in the simulations of both isolated and non
isolated self-gravitating! systems and of the luminosity profiles of
globular clusters and elliptical galaxies. We firstly discuss the
dynamics of an isolated cloud of particles and then we consider the
cosmological case. In this latter case the evolution such a structure represents a useful
toy model to test the accuracy of a cosmological N-body code in the non
linear regime. We show that the density profile of the virialized
structure can be strongly affected by numerical artifacts and that the
Navarro Frenk White density profile can be originated by numerical
problems. |
Mar 18 2014
14:00 |
|
Olindo Zanotti
(University of Trento)
|
General relativistic radiation-hydrodynamics of accretion flows |
ABSTRACT: I will discuss recent progress in the numerical modeling of
accretion flows made possible after solving the general relativistic
radiation-hydrodynamics equations within the projected symmetric
trace-free (PSTF) moment formalism. I will first present the necessary
numerical tools for coping with the stiffness of the equations and for
treating the intermediate regime between the optically thick and the
optically thin.
Then, I will show some applications to spherical accretion onto a black
hole, supersonic Bondi-Hoyle accretion and some preliminary results
about more realistic accretion discs. |
Mar 05 2014
14:00 |
room 135
|
Paul Mattew Sutter
(INFN)
|
Cosmic voids as cosmological laboratories |
ABSTRACT: Voids are the large, underdense regions in the cosmic web, and\r\nthey are potentially powerful cosmological probes due to their\r\nintimate connection to the growth of structure, their domination by\r\ndark energy, and their relative lack of systematics.\r\nI will present our latest work to identify voids in\r\ngalaxy redshift surveys, our efforts to understand their fundamental \r\nnature and their connection to dark matter underdensities,\r\nand an overview of many diverse cosmological applications, including\r\ngravitational lensing, the ISW effect, and the Alcock-Paczynski effect. |
Feb 25 2014
14:00 |
room 005
|
Carlo Burigana
(INAF-IASF Bologna;Dip. di Fisica e Scienze della Terra, Universita` di Ferrara)
|
Microwave and radio sky: synergies and perspectives |
ABSTRACT: Many cosmological and astrophysical problems in our rnunderstanding of the Universe evolution at early and late cosmic times rncan be addressed with a joint analysis of microwave and radio backgrounds. rnWhile the Planck mission is significantly improving cosmological model rndiscrimination and parameter estimation, the on-going and planned radio rnfacilities, such as LOFAR, SKA and its precursors, will put light on rnfundamental questions about cluster and intracluster medium and early rnstages of structure formation, providing also ancillary rninformation for a precise exploitation of future, ultra-accurate CMB rnmissions.
After a concise summary of the main Planck results, I will discuss the
joint implications of microwave missions and radio surveys for specific
themes, including the Sunyaev-Zeldovich effects at cluster and galaxy
scales, CMB spectral distortions, reionization and free-free signals,
cross-correlation between radio and CMB maps. |
Feb 24 2014
14:00 |
SISSA, Library Blue meeting room
|
Federico Bianchini
(SISSA)
|
|
ABSTRACT: Discussion on paper: 'Cosmology with doppler lensing', by Bacon et al., http://arxiv.org/abs/1401.3694 and on the most recent arXiv postings. |
Feb 18 2014
14:00 |
room 005
|
Michela Mapelli
(Padua Observatory)
|
the sarabande of stars and black holes in dense young star clusters |
ABSTRACT: Young star clusters are the nursery of stars in the local Universe and
are the site of dramatic dynamical processes. In particular, three-body
encounters (i.e. close encounters between a binary and a single star)
dominate the structural evolution of star clusters and influence the
formation of the so-called stellar exotica (i.e. peculiar objects of
stellar origin). Three-body encounters involving black holes are very
important for the formation of black-hole binaries, which may be
observed as X-ray binaries or as sources of gravitational waves.
In this talk, I present direct-summation N-body simulations of young
star clusters, in which we implemented metal-dependent recipes for
stellar evolution, stellar winds, and for the formation of stellar
remnants by direct collapse. I discuss the joint contribution of
three-body encounters and stellar winds in reversing the core collapse.
In particular, the post-collapse re-expansion of the core is weaker for
metal-poor star clusters than for metal-rich star clusters, because the
former lose less mass (through stellar winds) than the latter. As a
consequence, the half-mass radius expands faster in metal-poor star
clusters. Furthermore, I show that three-body encounters (and in
particular dynamical exchanges) dramatically affect the demographics of
black-hole binaries. The properties of X-ray binaries that underwent a
dynamical exchange are substantially different from those of primordial
binaries: the former host more massive black holes and start the
accretion phase later than the latter. Finally, exchanges produce a
population of double black hole binaries that is ten times more numerous
than the population of double neutron star binaries. This has important
implications for second-generation ground-based gravitational wave
detectors (Advanced LIGO and VIRGO). |
Feb 11 2014
14:00 |
SISSA, Room 005
|
Zhao Gongbo
(ICG, Porthsmouth)
|
Cosmological Tests of Gravity |
ABSTRACT: Abstract: In this talk, I will be presenting methods and results of
cosmological tests of gravity on both linear and nonlinear scales. On linear scales, I will introduce the principle component analysis (PCA) method for the model-independent gravity test and use this method to estimate the constraining power of future imaging and spectroscopic surveys. On nonlinear scales, I will present the high-resolution N-body simulations of modified gravity models and show the imprint of nonlinear screening effect on matter power spectrum and mass function. I will also talk about applications of these simulations, including a new GR test using the environmental effect, and a modified gravity extension of Halofit. |
Jan 28 2014
14:00 |
room 005
|
Francesco Pace
(ICG, Porthsmouth)
|
Lensing in coupled dark energy models |
ABSTRACT: Despite the LCDM model is at the moment the standard cosmological model able to virtually explain all present observations, from CMB to Large Scale Structure, it is still nevertheless important and interesting to test alternative hypothesis. One of the best methods that can be used to study gravity is weak gravitational lensing, the distortion of image source due to the matter distribution in the Universe.
I will discuss recent results and work in progress about lensing in Coupled Dark Energy models with the help of N-body and raytracing simulations and compare these results with a LCDM model. |
Jan 14 2014
14:00 |
room 005
|
Giulio Fabbian
(SISSA)
|
Detecting CMB polarization lensing with POLARBEAR |
ABSTRACT: The POLARBEAR experiment is one of the two ongoing ground-based rnexperiment hunting for the so-called B-modes of polarization of the Cosmic Microwave Background (CMB). According to the current cosmological model this signal can be generated mainly by two sources: primordial gravitational waves produced by an inflationary mechanism or by gravitational lensing of all the intervening large scale structures between us and the epoch of recombination. In this talk I will present the results of the first season data analysis effort of POLARBEAR which led to the first detection of the lensing effect on CMB polarization using CMB data alone. This result has also been confirmed through a cross correlation of the reconstructed lensing convergence power spectrum with biased tracers of large scales structure as observed by HERSCHEL. I will then discuss the advantages of polarized CMB lensing over more standard intensity based techniques for cosmological applications. |
Nov 19 2013
14:00 |
SISSA, Room 135
|
Aurel Schneider
()
|
Structure formation and alternative dark matter scenarios |
ABSTRACT: The talk will be about the connection between cosmological
structure formation and the nature of dark matter. I will focus on the
free-streaming of the dark matter fluid and it's effects on halo abundance.
Understanding this connection is crucial to constrain the dark matter
sector with astronomical observations. |
Nov 12 2013
14:00 |
SISSA, Room 005
|
Marcella Massardi
(INAF Bologna)
|
ALMA science: from Cycle 0 results to Cycle 2 preparation. |
ABSTRACT: The Atacama Large Millimeter Array (ALMA) Early Science operations have started at the end of September 2011.\r\nOver one hundred high science profile projects have been identified as\r\nhigh priority for execution. 97% of them and about 30 filler projects\r\nreceived ALMA data. The first exciting scientific results from Science\r\nVerification datasets and Cycle 0 observations are coming out in refereed journals since the beginning of 2012. In this talk we will quickly review some of the most impressive achievements of ALMA in its first Cycle of operations.\r\nWe will also summarize the status of the on-going Cycle 1 and the plans\r\nfor the Cycle 2 for which the call for Early Science proposals will be\r\nmade in October 2013 with a deadline for proposal submission in early\r\nDecember 2013. |
Oct 23 2013
14:00 |
SISSA, Room 005
|
Arianna Di Cintio
(Universidad Autonoma de Madrid)
|
The response of dark matter haloes to baryonic physics: cusps vs cores prediction in real galaxies |
ABSTRACT: We use a suite of simulated galaxies drawn from the MaGICC
project to investigate the effects of baryonic feedback on the density
profiles of dark matter haloes.
The main result is a clear dependence of the inner slope of the dark
matter density profile, on the ratio between stellar-to-halo mass.
We find that the most cored galaxies are expected to have
Vrot~50km/s while massive spirals, with Vrot>150km/s, are approaching
again the NFW profile.
We further extend our study and introduce a mass dependent density
profile for describing dark matter halos.
This novel prediction for cusps vs cores can be tested using
observational data sets and such mass dependent density profile can be
applied to semi-analytic galaxy formation models, and can be used in
observation when fitting rotation curve data. |
Oct 16 2013
14:00 |
SISSA, Room 135
|
Giulia Gubitosi
(University "La Sapienza", Rome, & INFN)
|
Disformal Coupling, CMB Spectral Distortion and Distance Duality Relation |
ABSTRACT: Light scalar fields can naturally couple disformally to Standard Modelrnfields without giving rise to the unacceptably large fifth forces usually associated with light scalars. We show that these scalar fields can be studied and constrained through their interaction with photons, and focus particularly on changes to the Cosmic Microwave Background spectral distortions and violations of the distance duality relation. We then specialize our constraints to scalars which could play the role of axionic quintessence. |
Jun 25 2013
14:00 |
Room 135
|
Javier Rodriguez Zaurin
(Instituto de Astrofisica de Canarias)
|
The importance of warm, AGN-driven outflows in rapidly evolving galaxies in the local universe. |
ABSTRACT: Although there is increasing speculation that the evolutionrnof galaxy bulges may be regulated by AGN-induced outflows associatedrnwith the growth of the central supermassive black holes, thernimportance of AGN-induced outflows relative to those driven byrnstarbursts has yet to be established observationally. In this contextrnwe have recently presented a study focusing on AGN-induced outflowsrnin a sample of local Seyftert-ULIRGs. Perhaps, our most interestingrnresult is related to the energy that the AGN returns to the galaxy inrnthe form of feedback. We find that the typical mass outflows ratesrnand kinetic powers of the emission line outflows are, in general,rnless energetically significant than the neutral and molecularrnoutflows in ULIRGs and moreover, than those required today in thernmajority of the current hydrodynamic simulations that include AGNrnfeedback. However, the uncertainties in the existing measurements arernlarge, and more accurate estimates of the radii, densities andrnreddening of the outflows are required to put these results on arnfirmer footing. In this context, we are using HST /ACS+STIS andrnVLT-Xhsooter observations to accurately estimate sizes, electronrndensities and reddening to eventually provide the most accuraternestimates of the kinetic powers associated with the ionized gas. Inrnthis talk I will describe in detail the results of this studyrnfocussing on testing the current simulations of hierarchical galaxyrnevolution. |
Jun 18 2013
14:00 |
Room 005
|
Reinard Beck
(University of Bohn)
|
Science with the Square Kilometre Array |
ABSTRACT: The Square Kilometre Array (SKA) is a new-technology radio telescope
planned for a dual-site construction between 2017 and 2025 in Southern
Africa and Australia. The precursor/pathfinder telescopes ASKAP
(Australia), MeerKAT (South Africa) and LOFAR (Europe) are already operating.
Five key science projects have been defined for the SKA. With help of
pulsars signals, the SKA will constrain theories on gravitation. Radio waves carry signals from gas clouds from the Epoch of Reionization, emitted even before the formation of the first stars. The evolution of galaxies will be traced by observing the HI line out to large redshifts. The structure of protoplanetary systems can be observed from their thermal radio emission. The SKA will also open a new era in the observation of magnetic fields and help to understand their origin. An all-sky survey of Faraday rotation measures towards a dense grid of polarized background is dedicated to measure magnetic fields in distant intervening galaxies and in intergalactic filaments. |
Jun 12 2013
13:45 |
Room 135
|
Mahavir Sharma
()
|
Outflows from galaxies and AGN |
ABSTRACT: Galactic outflows are multiphase hydrodynamic phenomena observed in various wavelengths, and are thought to be driven by supernovae and AGN activity. They are important as a feedback process for galaxy formation and evolution. In this talk, I will discuss new results from our study of these multiphase outflows from hydrodynamical and cosmological perspective. We find that supernovae driven outflows can escape only from low mass galaxies and their speeds rarely exceed 1000 km/s. On the other hand, AGN momentum injection can drive outflows from massive galaxies with speeds exceeding this limit.\r\nThis result provides a useful diagnostic, and is also supported by observations. We also derive the relation between stellar and halo mass for galaxies undergoing outflows, and compare with observations. \r\nWe also study the interaction of a free wind with the hot halo gas, and quantify the conditions for the escape of free wind from galaxies. \r\nWe find that the extraplanar cold/warm clouds can be formed in these interaction zones via fluid instabilities. We have developed a radiation and ram pressure driven outflow model to study the cold/warm phase of outflows and show different regimes of SFR and galactic mass in which ram and/or radiation pressure dominates. Recently we have also carried out an observational study to explore the possibility that MgII absorbers in quasar sightlines are associated with quasar radiation driven outflows. |
Jun 11 2013
14:00 |
Room 005
|
Joao Maguejo
()
|
Dimensional reduction in the sky? |
ABSTRACT: I review the popular idea that at high energies space-time becomes 2 dimensional, thereby simplifying the task of quantum gravity. I then present some recent work on the cosmological implications of this phenomenon. |
Jun 04 2013
14:00 |
Room 005
|
Paolo Natoli
(Università degli studi di Ferrara)
|
Cosmology with Planck |
ABSTRACT: I will present highlights from the 2013 Planck cosmology release
and discuss their significance. The Planck results widely support the
standard LCDM model, whose parameters are measured with increased accuracy.
In a few cases, this results in values sensibly different from those earlier accepted. Planck sets new limits on the total neutrino mass and number, as well as on several inflationary parameters, and has measured CMB lensing at 25 sigma. The statistics of the CMB anisotropies has is now constrained to high accuracy. At the same time, Planck has yielded increased evidence for anomalies in the CMB temperature field that many find uneasy to accommodate within the accepted paradigm. |
May 28 2013
14:00 |
Room 005
|
Adriano Fontana
(INAF, Roma)
|
The earliest CANDELS in the Universe. |
ABSTRACT: Understanding the early phase of galaxy evolution is one of the major goal of modern astrophysics.
Deep surveys that uses a combination of state-of-the-art instruments to
explore the highest redshifts are a fundamental tool in this context.
The most recent and ambitious is the Cosmic Assembly and Dark Energy Legacy Survey (CANDELS; PI: S. Faber, Co-PI: H. Ferguson), the largest HST project ever undertaken.
CANDELS began in late 2010 and is close to completion. CANDELS represents the natural extension of the previous deep/wide surveys executed with HST and other space telescopes (like GOODS and COSMOS) that have revealed the evolution of galaxies at high redshift.
In my talk I will first present the current status of the survey and of the ancillary data that are being taken, with a special emphasis on the Hawk-I VLT followup of the southern CANDELS fields. I will also briefly describe some of the earliest scientific results from the survey, with a special emphasis on the statistics and properties of high redshift galaxies and AGNs: the assembly of statistically useful samples of galaxies at 6 < z < 9, measurement of the morphology and internal color structure of galaxies at z = 2−3, the evolution of massive and quiescent galaxies at high redshift. |
May 14 2013
14:00 |
Room 135
|
Rosalba Perna
(Chicago University)
|
Title Gamma-Ray Bursts as Tools for Extragalactic Astrophysics and Cosmology |
ABSTRACT: Gamma-Ray Bursts (GRBs) are the brightest light sources in thernUniverse, as well as the most distant sources known. Theserncharacteristics, combined with their powerlaw spectra, make them ideal cosmological probes. In this talk I will discuss how GRBs are impacting several areas of extragalactic astrophysics and cosmology. In particular, I will show how they can be used to trace the evolution of the mean density and clumpiness of the interstellar medium with redshift, andthe properties of dust in high-z galaxies. Detection of GRBs at very high redshifts can help set constraints on the small-scale power spectrum of density fluctuations. High-resolution observations of long GRBs allow to shed light on the properties of their massive star progenitors. Statistical studies of short GRBs can improve our understanding of evolutionary binary scenarios. |
Apr 30 2013
14:00 |
SISSA - Room 005
|
Yannick Mellier
(IAP)
|
Euclid … digging the dark in the Planck Universe … |
ABSTRACT: Euclid is an ESA M-class mission that was selected in October 2011. Euclid
aims at understanding the origin of the accelerating expansion of the
Universe by observing signatures of dark energy, modified gravity and dark matter on the expansion history and the growth rate of cosmic structure.
Euclid will use 5 complementary and/or independent cosmological probes: weak lensing, baryon acoustic oscillations, redshift-space distortion, clusters of galaxies and integrated Sachs-Wolf effect. The payload module will be composed of a 1.2 meter telescope that will feed a wide field high image quality optical imager and a field field near-infrared photometer and spectrometer. The instruments will measure the shapes of about 1.5 billion galaxies and redshifts of 50 millions galaxies observed over the whole darkest extragalactic sky (15,000 square degrees). In this review, I will present the mission and its goals and will show how Euclid will be used to pin down the properties and the history of the dark Universe. |
Apr 23 2013
14:00 |
Room 005
|
Massimo Meneghetti
(INAF, Bologna)
|
New challenges for lensing by galaxy clusters |
ABSTRACT: Gravitational lensing is among the most powerful tools for investigating
the mass distributions in the universe and constrain the cosmological
model. Galaxy clusters are the largest and the most powerful lenses in
the universe and both the strong and weak lensing regimes can be used to
probe their structure. Additionally, their magnification effect allow to
give a deeper view into the high-z, early universe. Ongoing programs
like the CLASH MCT and the upcoming Frontier Fields Initiative are or
will be targeting galaxy clusters with the Hubble Space Telescope and
other ground based facilities o fully exploit these potentialities.
These observational campaigns will also be the basis upon which the next
generation of cluster lensing surveys, like those which will be
performed by Euclid, will be built.
After reviewing some recent results, I will discuss with the help of
numerical simulations, how we are trying to assess the systematics and
improve the methodologies of the lensing analysis in order to be ready
for the next challenges to come. |
Apr 16 2013
14:00 |
Room 135
|
Radek Wojtack
(DARK, Copenhagen)
|
Three selected examples of what we can learn from galaxy kinematics |
ABSTRACT: Galaxy kinematics is a powerful means of studying astrophysical
objects at all scales, from dwarf spheroidals to galaxy clusters. In my talk, I will present three examples of kinematic analysis aimed at measuring three different astrophysical effects or properties. The first is detection of gravitational redshift caused by gravitational potential of galaxy clusters. This measurement is based on a combined analysis of galaxy velocities in ~7800 clusters selected from SDSS. As the second instance, I will show constraints on the mass-concentration relation of dark matter haloes in the early and late type galaxies, obtained in dynamical analysis of satellite galaxies. Finally, I will present the first present results of an ongoing project of constraining the 3D shapes of galaxy clusters and their velocity ellipsoids. |
Apr 09 2013
14:00 |
Room 005
|
Roberta Paladini
(Caltech)
|
HII regions: a window on dust physics. - From dust evolution to Anomalous Microwave Emission |
ABSTRACT: The depletion of dust grains in the ionized gas is predicted by models and observed both in HII regions and in the diffuse ionized gas. However, the mechanism responsible for this depletion has yet to be clearly identified. After a brief review of the possible depletion scenarios, I will present the results of the analysis of a sample of Galactic evolved HII regions performed by combining IRAC 8 micron, MIPS 24 micron, PACS 70/160 micron and SPIRE 250, 350, 500 micron data. The analysis shows that dust inside HII regions is depleted mostly due to radiation pressure driven drift, as recently proposed by Draine (2011). In addition, we also find that radiation pressure induces a selection of the size of the grains, with the surviving grains being either small Big Grains (a ~ 0.01 micron) or large PAHs (a ~ 0.005 micron). In the last part of my talk, I will discuss implications of studies of HII regions for Anomalous Microwave Emission (AME), a recently discovered emission mechanism commonly attributed to spinning dust. |
Mar 26 2013
14:00 |
Room 135
|
Luigi Piro
(INAF, Rome)
|
Gamma-Ray Bursts: status and perspecitives |
ABSTRACT: I will review the observational body of GRB observations,
discussing the implications on theoretical scenario. Particular emphasis will be given to high energy observations, and the importance of GRB as probes of small and large scale structures from high redshift to the closer
Universe. I will finally discuss the panorama of future observational perspectives. |
Mar 19 2013
14:00 |
Room 135
|
Anna Bonaldi
(Jodrell Bank Centre for Astrophysics, University of Manchester)
|
Planck intermediate results. XII: Diffuse Galactic components in the Gould Belt System |
ABSTRACT: We perform an analysis of the diffuse low-frequency Galactic
components in the Southern part of the Gould Belt system (Galactic longitude 130-230 degrees, Galactic latitude -15 - -10 degrees). Strong UV flux coming from the Gould Belt super-association is responsible for bright diffuse foregrounds that we observe from our position inside the system and that can help us improve our knowledge of the Galactic emission. Free-free emission and anomalous microwave emission (AME) are the dominant components at low frequencies ( < 40 GHz), while synchrotron emission is very smooth and faint. We separate diffuse free-free emission and AME from synchrotron emission and thermal dust emission by using Planck data, complemented by ancillary data, using the ``Correlated Component Analysis'' (CCA) component separation method and we compare with the results of cross-correlation of foreground templates with the frequency maps.
We estimate the electron temperature Te from Halpha and free-free emission using two methods (temperature-temperature plot and cross-correlation) and we consistently obtain Te ranging from 7000 to 2000 K for a dust absorption fraction of 0-0.5. We estimate the frequency spectrum of the diffuse AME and we recover a peak frequency (in flux density units) of 25.5 +- 1.5 GHz. We verify the reliability of this result with realistic simulations that
include the presence of biases in the spectral model for the AME and in the free-free template. By combining physical models for vibrational and
rotational dust emission and adding the constraints from the thermal dust spectrum from Planck and IRAS we are able to get a good description of the frequency spectrum of the AME for plausible values of the local density and radiation field. |
Mar 05 2013
14:00 |
Room 128
|
Eiichiro Komatsu
(Max Planck Institute for Astrophysics)
|
The Wilkinson Microwave Anisotropy Probe (WMAP) Observations: The Final Results |
ABSTRACT: he Cosmic Microwave Background (CMB), the fossil light of the Big Bang,
is the oldest light that one can ever hope to observe in our Universe. The
CMB provides us with a direct image of the Universe when it was still an
"infant" - 380,000 years old. The Wilkinson Microwave Anisotropy Probe
(WMAP) has mapped the microwave sky in five frequency bands for nine
years since 2001, creating a full-sky CMB map with the unprecedented
precision.
The WMAP data have enabled us to obtain a wealth of cosmological
information, such as the composition, age, geometry, and history of the
Universe. Yet, can we go further and learn about the primordial universe,
when it was much younger than 380,000 years old, perhaps as young as a
tiny fraction of a second? If so, this gives us a hope to test competing
theories about the origin of the Universe at ultra high energies. In this
talk, we will review the physics of CMB and the WMAP mission, present the
basic results from nine years of observations, and discuss their
cosmological implications. |
Feb 27 2013
14:30 |
SISSA - Aula Magna
|
Frans Prestorius
(Princeton University)
|
SISSA Colloquium - Black holes: probes of the cosmos and fundamental physics |
ABSTRACT: Frans Pretorius, Professor of Physics at Princeton University, will talk about black holes, one of the most fascinating predictions of Einstein's theory of general relativity. |
Feb 13 2013
11:30 |
Room 005
|
Richard Davies
(Max Planck Institute for Extraterrestrial Physics)
|
Does star formation play a decisive role in feeding AGN? |
ABSTRACT: While the existence of a starburst-AGN connection is undisputed, there is no consensus about what that really means or if any such connection is causal.
In this talk, I will begin by looking at whether large scales are important in fuelling AGN. I will then turn to recent high resolution observations that are able to probe the central tens of parsecs where star formation might influence AGN activity. I show that both the starburst phase and the physical state of the dense molecular gas imply that stellar feedback plays a critical role in first hindering and then helping accretion. I argue that AGN are associated with young post-starbursts, and that it is only after the early turbulent phases of a starburst that gas from slow stellar winds can accrete efficiently to smaller scales. And I outline other contexts where similar processes appear to be at work. I finish by showing how the properties of the obscuring torus are directly coupled to this star formation, and that we should be thinking of the torus as a complex dynamical entity. |
Feb 05 2013
14:00 |
Room 005
|
Gianfranco Gentile
(University of Ghent)
|
MOND - Modified Newtonian Dynamics: an observational perspective |
ABSTRACT: Astronomical observations at most scales point towards the
presence of a mass discrepancy, which can (in principle) be interpreted as the presence of additional mass (dark matter) or as our failure to understand gravity at low gravitational accelerations. One of the most successful theories of modified
gravity is MOND, Modified Newtonian Dynamics. I will review the phenomenological properties of MOND (focussing on the galaxy scale), from the motivation to explain observations to the current challenges faced by MOND. I will also discuss the pros
and cons of MOND and current dark matter theories. |
Jan 29 2013
15:00 |
Room 005
|
Andrea Possenti
(Cagliari Observatory)
|
Detecting gravitational waves from cosmological distances |
ABSTRACT: Radio pulsars are neutron stars emitting collimated beams of radio waves, observed as pulses, once per neutron star rotation. Due to evolutionary reasons and intrinsic properties, some pulsars behave as highly stable clocks and the measurement of the times of arrival of their pulses can provide an accurate determination of their positional, kinematic, spin and orbital parameters, as well as indications on the properties of their space-time environment. This provides the observational basis for using the pulsars as tools for testing the gravity theories in a strong field regime. The talk will describe the theoretical and experimental methodology for performing some of these tests, focusing on the case of the Pulsar Timing Array(s), which are the most promising approach for a direct detection of the gravitational waves in the nanoHz frequency range, likely produced by (an ensemble or single) sources located at cosmological distances. |
Jan 15 2013
14:00 |
Room 005
|
Ben Granett
(INAF, Brera)
|
Observing the growth of structure through the Integrated Sachs-Wolfe effect |
ABSTRACT: Large-scale structures at low redshift leave an imprint on the cosmic microwave background radiation through the integrated Sachs-Wolfe effect. The phenomenon depends on the time evolution of the
gravitational potential on extremely large scales and gives a unique measure of the cosmic acceleration due to dark energy. I will review cross-correlation measurements as well as direct methods using matched filter and stacking techniques. Recent results with WISE infrared-selected galaxies will be presented.
Over the past 15 years, measurements of the effect have reached the 4sigma confidence level with survey volume being the most limiting factor.
Future galaxy surveys co-analysed with Planck maps promise to increase the measurement precision and bring better control over systematic errors |
Jan 09 2013
14:00 |
Room 135
|
Franco Vazza
(Hamburg Observatory and INAF-Istituto di Radio Astronomia, Bologna)
|
Shocks, turbulence and non-thermal phenomena in galaxy clusters: a view from cosmological grid simulation |
ABSTRACT: Radio observations of galaxy clusters in a merging state show evidence of relativistic electrons and magnetic fields spread on Mpc scales. The source of acceleration of such electrons is still debated. I will discuss possible source of acceleration connected to the dynamics of the intra cluster medium, and I will present recent theoretical advancements achieved using high resolution cosmological simulations using a grid approach. Fermi I and II mechanisms seems to be the key ingredients to explain such phenomena, yet the efficiency of the acceleration of cosmic ray electrons during mergers is unknown, and the present non-detection of clusters in gamma rays poses strong limitations to the acceleration of cosmic ray protons in the same processes. |
Nov 27 2012
16:00 |
Room 005
|
Dave Clements
(Imperial College)
|
Herschel, Planck and the High Redshift Universe |
ABSTRACT: The far-IR/submm band from 200 to 500 microns has been largely unexplored until very recently. Since their launch, in May 2009, Herschel and Planck have been exploring this waveband and providing new insights into a wide range of astrophysics. This talk focuses on the high redshift (z>1) universe and will discuss gravitational lenses, galaxy clusters and the search for the highest redshift dusty galaxies. It is still early days for the exploitation and followup of Herschel and Planck surveys, but it is already clear that these missions will have a major impact on our understanding of dusty galaxies at high redshift. |
Nov 20 2012
14:00 |
Room 005
|
Lucio Mayer
(University of Zurich, and ETH Zurich)
|
The Eris disk galaxy formation simulations: realistic spiral galaxies with pseudobulges and effects of baryons on the dark halo |
ABSTRACT: I will review the results of the Eris suite of hydrodynamical cosmological simulations, which succeed in forming realistic late-type spiral galaxies within the LCDM cosmology owing to a combination of unprecedemted resolution and a high density threshold for star formation micmicking how star formation occurs in clumpy molecular gas. I will show that the bulge of such galaxies is an old pseudobulge such as that of our own Milky Way and describe its formation path that is neither due to mergers nor to conventional secular evolution. I will also discuss results on the effect of the baryons on the dark matter halo, including the origin of a relative offset between the density peak of the two components that might explain recent findings by the Fermi satellite. |
Nov 06 2012
16:00 |
Room 005
|
Carlotta Gruppioni
(INAF, Osservatorio di Bologna)
|
The Herschel PEP+HerMES Luminosity Function: Probing the evolution of IR galaxies up to z~4 |
ABSTRACT: We exploit the deep and extended far-infrared data-sets of the Herschel GTO PACS Evolutionary Probe (PEP) Survey, in combination with the Herschel
Multi-tiered Extragalactic Survey (HerMES) data at 250, 350 and 500 micron, to derive the evolution of the total IR luminosity functions (LFs) of galaxies
and AGN from z=0 to z~4. We detect very strong luminosity evolution for the total IR LF, with L_IR~(1+z)^3.55 up to z~2, and ~(1+z)^1.62 z~2 and z~4,
combined with a density evolution ~(1+z)^(-0.57) up to z~1 and ~(1+z)^(-3.93) between z~1 and z~4. In agreement with previous findings, the IR luminosity
density (LD) increases steeply to z~1, then flattens between z~1 and z~2, to decrease at z>2. Galaxies occupying the well established SFR-stellar mass
main sequence (MS) are found to dominate both the total IR LF and luminosity density at all redshifts, with the contribution from off-MS sources
(>0.6 dex above MS) being nearly constant (~20% of the total LD) and showing no significant signs of increase with increasing z over the whole 0.82) LF. A two-fold evolutionary scheme for IR galaxies is suggested: on the one hand, the AGN-dominated population (both type 1 and 2), evolving in a similar way, is detected in far-IR surveys during an active starburst phase (possibly triggered by a major merging
event also feeding the SMBH), preceding a red, spheroidal phase. On the other hand, the low-luminosity AGN, or LLAGN, have various properties that suggest they are good candidates for systems in a (long-lasting, i.e. few 10^9 yrs) transition phase between gas-rich starbursts and steady spiral galaxies. |
Oct 30 2012
16:00 |
Room 005
|
Gigi Guzzo
(INAF, Osservatorio di Brera)
|
Galaxy clustering: an increasingly stringent probe of cosmology |
ABSTRACT: I will review recent observational and modelling work to extract cosmological information from galaxy redshift surveys.
Redshift surveys allow us to measure both the expansion history H(z) and growth rate of structure f(z), which can be combined to disentangle the origin of cosmic acceleration, distinguishing dark energy from modified gravity. I will concentrate in particular on the use of redshift-space distortions to measure f(z), presenting early results from the ongoing VIPERS project at ESO. An important issue in the context of "precision cosmology" concerns the accuracy of current modeling in terms of systematic effects.
I will show recent work on this issue and discuss future prospects, also in view of the recently funded ERC project "DARKLIGHT". |
Oct 23 2012
16:00 |
Room 005
|
Alexei D. Beklemishev
(Novosibirsk State University and Budker Institute of Nuclear Physics)
|
Magnetic mirrors; history, results and fusion prospects |
ABSTRACT: The talk reviews milestones of 60-year long development of magnetic mirrors for fusion, relevance of mirrors for current plasma and materials science, and their prospects as neutron sources, drivers for fission-fusion hybrids, or pure-fusion reactors. The evolution of open traps brought them from simple solenoids to highly sophisticated and huge tandem mirrors with quadrupole magnetic stabilizers. They lost competition to tokamaks and are close to extinction. A side branch of open traps went for engineering and physics simplicity inherent in axially symmetric mirrors. Since simplicity means lower cost of construction and servicing, lower engineering and materials demands, such traps might regain an edge over tokamaks, which grew huge and expensive.\r\nThe emphasis is made on physics and development of axially symmetric magnetic mirrors at the Budker Institute of Nuclear Physics in Novosibirsk that currently represent the frontline of mirror research. In particular, we discuss experimental results from the multiple-mirror trap GOL-3 [1] and the gas-dynamic trap GDT [2], and their relevance to fusion. The next step in this line of research is the GDMT program that will combine the GDT-style central mirror with multiple-mirror end plugs in a modular superconducting device.\r\n\r\n[1] A.Burdakov, A.Ivanov, E.Kruglyakov, Plasma Phys. Control. Fusion, 52 (2010) 124026.\r\n[2] A. Ivanov, Fusion Science and Technology. 59 No.1t (2011) 17. |
Oct 18 2012
16:00 |
Room 005
|
Vitor Cardoso
(CENTRA, IST, Lisbon)
|
Black holes: alive, kicking and exploding |
ABSTRACT: Black holes are the elementary particles of gravity, and play a crucial role in fundamental physics, astrophysics,
high energy physics and particle physics. In the last 5 years, our ability to understand strongly nonlinear
phenomena involving black holes has opened up a new Golden Age in the field. From Cosmic Censorship tests to superkicks and black hole bombs, the possibilities are endless. I will describe some of the current activity in
the field along with prospects for the future. |
Oct 09 2012
16:00 |
Room 005
|
Pierre Salati
(Laboratoire d'Annecy-le-Vieux de Physique Théorique)
|
Dark matter Indirect Detection and the Cosmic Ray Anomalies |
ABSTRACT: A century after their discovery by Victor Hess, cosmic rays are still an exciting field of research, in particular because they could provide indirect but crucial informations
on the astronomical dark matter. The nature of this essential component of the universe is still unknown. Weakly interacting and massive particles (WIMP) have been suggested
as plausible candidates. Should these putative species exist, they would continuously annihilate within the Milky Way halo, yielding rare antimatter particles -- antiprotons and
positrons -- which would distort the astrophysical backgrounds.The discovery in 2008 of a cosmic ray lepton anomaly has raised the tremendous hope that WIMPs were not just a fantasy. Alas, the dust has now settled down. Local pulsars are suggested as the probable source of the positron excess. Modeling correctly the galactic cosmic radiation turns out to be a crucial ingredient in the quest for dark matter. I will present how it is currently modeled. I will discuss various indirect signatures for WIMPs and will pay particular attention to the astrophysical backgrounds inside which the various signals are hidden. I will finally explain why our current description of cosmic ray propagation -- on which public codes like GALPROP, DRAGON or USINE are built --
needs to be revised and, as a concluding remark, will discuss an explanation of the proton and helium anomalies observed by PAMELA et CREAM. |
Oct 02 2012
16:00 |
Room 005
|
Levon Pogosian
(Simon Fraser University)
|
Fables of reconstruction: examining the evidence for dynamical dark energy |
ABSTRACT:
I will describe a new non-parametric Bayesian method for reconstructing the evolution history of the dark energy equation of state, based on applying a correlated prior for w(z). When applied to the latest supernova, CMB, redshift space distortion and the baryonic acoustic oscillation measurements, it mildly favors a dynamical dark energy model which evolves across w=-1. However, an examination of the Bayesian evidences shows little preference between the cosmological constant model and the dynamical model for a range of correlated prior choices. On the other hand, we show that the best fit models for current data will be well distinguished from the LCDM model by future observations. |
Jul 03 2012
16:00 |
Room 005
|
Ted Jacobson
(University of Maryland)
|
Induced aether action from UV Lorentz violations |
ABSTRACT: Lorentz violating (LV) modifications of Einstein gravity have been explored as possible avatars of UV LV, with arbitrary coupling parameters. I will discuss models in which these parameters can be computed from UV LV physics. The models are motivated by the notion of cosmological UV mode creation, but could also arise from other forms of UV LV physics. |
Jun 26 2012
16:00 |
Room 005
|
Fabrizio Tamburini
(University of Padova)
|
Einstein gets a twist…The orbital angular momentum of light in Astronomy and Astrophysics |
ABSTRACT: |
May 29 2012
16:00 |
Room 005
|
Giulia Gubitosi
(APC Paris)
|
Testing Lorentz symmetries with CMB polarization data |
ABSTRACT: Lorentz symmetry violations are expected to emerge when spacetime is probed on very short distance scales, of the order of the Planck length ~10^(-35) m and can produce anomalous light propagation. CMB photons provide a way to test spacetime on these very small scales thanks to their long propagation time, that amplifies deviations from standard light behavior.
The kind of anomalies we are interested in would show up as a birefringent behavior of light, which can possibly depend on the propagation direction if space isotropy is also violated.
We present the current constraints on isotropic birefringence and show that polarization data gathered by the PLANCK satellite will reach the sensitivity required to test spacetime symmetries up to the Planck-scale. Moreover, we show that the availability of an almost full-sky coverage can allow to perform also accurate tests on non-isotropic birefringence effects. |
May 22 2012
16:00 |
Room 005
|
Paolo Pani
(CENTRA, Lisbon)
|
Perturbations of slowly rotating black holes |
ABSTRACT: We present a general method to study linear perturbations of slowly rotating black holes which is valid for any perturbation field, and particularly advantageous when the field equations are not separable. As an illustration of the method we investigate massive vector (Proca) perturbations in the Kerr metric, which do not appear to be separable in the standard Teukolsky formalism.We discuss two important first-order effects induced by rotation: a Zeeman-like shift of nonaxisymmetric quasinormal modes and bound states with different azimuthal number $m$, and the coupling between axial and polar modes with different multipolar index $\ell$. We discuss evidence that Proca fields exhibit a significantly stronger superradiant instability than massive scalar fields. We estimate that observations of spinning astrophysical black holes should provide the tightest known upper limits on the mass of the photon. We conclude by discussing further applications of the method and its extension to second order. |
May 15 2012
16:00 |
Room 005
|
Enrico Barausse
(University of Guelph)
|
The evolution of the spins of massive black holes |
ABSTRACT: After reviewing the importance of black-hole spins in general relativity, astrophysics and cosmology, I will present a semianalytical model following the coevolution of the spins of massive black holes and their host galaxies. Besides showing results for the spin evolution of massive black holes as a function of redshift, I will discuss the implications of my model for future space-based gravitational-wave detectors. |
May 08 2012
16:00 |
Room 005
|
Valerio Faraoni
(Bishop's University)
|
Cosmological wormholes |
ABSTRACT: Exact solutions of general relativity describing a wormhole embedded in a cosmological background (other than the static de Sitter one) are not hard to construct, although they are almost unknown in the literature. Three classes of such solutions will be introduced: the first two describe thin shell wormholes endowed with exotic energy and embedded in a universe approaching the Big Rip. The last class describes a Lemaitre-Tolman-Bondi thin shell wormhole embedded in a dust-dominated background. Contrary to expectations, this wormhole shell hosts matter satisfying the weak, strong, and null energy conditions, with the implication that maybe time travel assisted by dynamical wormholes does not require exotic energy after all. |
Apr 24 2012
16:00 |
Room 005
|
Nigel Mitchell
(University of Vienna)
|
A Multi-Phase Chemodynamic ISM Model in FLASH using Stellar Hydrodynamics |
ABSTRACT: We present our motivation for the development of a true multi-phase ISM
model in the FLASH code which can split the cold compact molecular component from the hot tenuous gas phase of an otherwise unresolved ISM.
In particular we highlight how single phase ISM models in both SPH and AMR codes produce different results, highlighting the need for more sophisticated and robust models for the ISM.
In FLASH, instead of using the standard particle-mesh approach for the near collisionless molecular clouds and the stellar particles, we choose to implement a brand new stellar hydrodynamic solver which allows us to model collisionless matter as a fluid on the mesh. We present our early results from the model and outline the many advantages of such a technique. |
Apr 03 2012
16:00 |
Room 005
|
Angela di Virgilio
(INFN PISA)
|
An Array of Ring Lasers to measure the Frame Dragging of the Earth |
ABSTRACT: Ringlasers are top sensitivity and accuracy instruments, able to measure angular velocity. G, a large ring installed in the laser ranging station of Wettzell measures the Earth angular velocity with an accuracy not far from 1 part in 109. Such accuracy is so high that in the near future, general relativity effects due to the curvature of space-time around the Earth (de Sitter effect) and to the rotation of the planet (dragging of the inertial frames or Lense-Thirring effect) can be measured. It is based on the comparison between the IERS value of the Earth rotation vector and the corresponding measurements obtained by a tri-axial laser detector of rotation. The experimental apparatus is an array of several rings located inside an underground facility, in our design six large ring-lasers along three orthogonal axes, following the shape of an octahedron. In about two years of data taking, the 1% sensitivity required for the measurement of the Lense-Thirring drag can be reached with square rings of 6 m side, assuming a shot noise limited sensitivity (formula). This apparatus could be installed inside the INFN GranSasso National Laboratory, the first drawings of the experimental apparatus will be discussed. |
Mar 27 2012
16:00 |
Room 128
|
Hector De Vega
(LPTHE, Paris VI)
|
Warm Dark Matter and Galaxy Structure in the Standard model of the Universe |
ABSTRACT: |
Mar 06 2012
16:00 |
SISSA, room 005
|
Ravi Sheth
(ICTP)
|
Photometric redshift surveys: Drinking tea with a fork? |
ABSTRACT: The next generation of sky surveys will provide photometric rather thans pectroscopic redshifts. Considerable effort has gone into using these noisy distance estimates to place sharp constraints on cosmological parameters. I will describe methods which turn such surveys into effective constraints on models of galaxy formation as well. Along the way I will discuss progress and open questions in generating the accurate mock galaxy catalogs which will play an important role in this era of precision astrophysics. |
Feb 28 2012
16:00 |
SISSA, Room 005
|
Susana Planelles
(OATS/INAF)
|
Exploring gravitational feedback processes in a cosmological context |
ABSTRACT: Present-day hydrodynamics/N-body simulations still present important discrepancies with
the observations, especially in the inner regions of massive galaxy clusters. These
discrepancies have motivated the idea that, besides gravity and adiabatic gas dynamics, non-gravitational processes related with the baryonic component of the Universe need to be included in simulations. Nevertheless, within this context, it is also crucial to properly describe the different gravitational processes inherent to the hierarchical formation of cosmic structures. In this
contribution, making use of an Eulerian cosmological code and a grid-based halo finder, we will analyse the role played by galaxy cluster mergers, as well as by the cosmological shock waves developed during these events, as sources of feedback and reheating of the ICM in a full cosmological context. We will pay especial attention to discuss the role of these merger
events on the existence of cool cores in galaxy clusters, as well as in the scaling relations. |
Feb 21 2012
16:00 |
SISSA room 005
|
Marcel Clemens
(OAPD)
|
Some Results from the Herschel Virgo Cluster Survey (HeViCS) |
ABSTRACT: I will give a broad overview of some of the more interesting results that have so far come out of a Herschel survey of the Virgo cluster. The survey covered a continuous area of 84 square degrees in 5 bands from 100-500 micron. |
Jan 31 2012
16:00 |
Room 005
|
Lorenzo Sironi
(Princeton University)
|
Particle Acceleration in Relativistic Magnetized Astrophysical Shocks |
ABSTRACT: The termination shock of pulsar winds and internal shocks in gamma-ray bursts and AGN jets are likely to be seeded with a substantial magnetic field (ratio "sigma" of magnetic to kinetic energy density > few percent), oriented mostly perpendicular to the shock normal. By means of particle-in-cell simulations, we study how the efficiency of particle acceleration in relativistic shocks depends on the magnetization of the pre-shock flow and the geometry of the upstream field. We study both uniform and alternating pre-shock fields. For uniform fields, we find that if sigma>0.001 only nearly-parallel shocks lead to particle acceleration. For quasi-perpendicular shocks, the self-generated turbulence is not strong enough to give appreciable acceleration of particles. In contrast, if the pre-shock medium consists of stripes of alternating field and sigma>>1, dissipation of the stripes when compressed at the shock front can transfer energy from the field to the particles, resulting in nonthermal acceleration. Our findings place important constraints on the models of non-thermal radiation from Pulsar Wind Nebulae, gamma-ray bursts and AGN jets that invoke particle acceleration in relativistic magnetized shocks. |
Jan 10 2012
16:00 |
Room 005
|
Pierluigi Belli
(Roma "Tor Vergata")
|
Signals from the Dark Universe: the annual modulation results by DAMA/LIBRA |
ABSTRACT: The DAMA/LIBRA set-up (about 250 kg highly radiopure NaI(Tl)) is running
at the Gran Sasso National Laboratory of the INFN. The results of six annual cycles exploiting the model independent annual modulation signature for dark natter particles in the galactic halo will be discussed (exposure of 0.87 ton x yr). The cumulative exposure with those previously released by the former DAMA/NaI is 1.17 ton × yr, corresponding to 13 annual cycles. The confidence level for the observed effect is 8.9 sigma and the data satisfy all the many requirements of the dark matter annual modulation signature. In particular, the measured phase and the measured period are well in agreement with those expected for the dark matter particles. Presently DAMA/LIBRA is in data taking in the new configuration.Results, implications and experimental perspectives will be summarized. |
Dec 13 2011
16:00 |
SISSA 005
|
Jean-Claude Waizmann
(INAF - Osservatorio Astronomico di Bologna
)
|
How pink are pink elephants? - An application of extreme value statistics to the most massive galaxy clusters at low and high redshift
|
ABSTRACT: In this talk I present an application of extreme value statistics to the most massive galaxy clusters at high and low redshifts. I will talk about the distribution functions of the most massive galaxy clusters in a given survey area and I will discuss the effects that shall be taken into account for a statistical analysis.
In the second part of my talk, I will also analyze the idea to use the cumulative distribution function of the most massive haloes as a cosmological probe, discussing its advantages and drawbacks. |
Dec 01 2011
16:00 |
SISSA, Room 005
|
Kostas Kokkotas
(Tuebingen University and University of Thessaloniki)
|
Neutron Stars: Rotational and Magnetic Field Instabilities |
ABSTRACT: We will present recent results from the Tuebingen group related to rotational instabilities of neutron stars, their importance to gravitational wave detection and to asteroseismology. In addition, we will discuss the results of our study for the magnetic field instabilities and their relation to emission of gravitational waves from magnetars. |
Nov 22 2011
16:00 |
SISSA, Room 005
|
Paolo Molaro
(OATS)
|
The star that should not exist |
ABSTRACT: Metal-poor stars are records of the chemical composition of the young Galaxy or even relics of pre-galactic phases. They are quite rare objects and provide information on the chemical enrichment and on the type of the first stellar objects. Not clear how metal poor they can be and current theories predict the existence of a threshold in metallicity to form low mass stars that could be observed today.
In the last years we developed an automatic procedure to select metal poor candidates from the Sloan Digital Sky Survey. Some of these were observed during the GTO of the spectrograph X-Shooter and their low metallicity confirmed. We also succeeded in finding out a record metal-poor star with a metallicity of [Fe,C,N/H] ~ -5.0 (Caffau et al Nature 477, Sept 2011). Quite surprisingly the star does not show evidence of Li. Some of the implications of this discovery will be briefly discussed. |
Nov 08 2011
16:00 |
SISSA, Room 005
|
Chris Byrnes
(CERN)
|
Maximizing the scientific return from cosmic non-Gaussianity |
ABSTRACT: The model of local non-Gaussianity, parameterised by the constant non-linearity parameter fNL, is an extremely popular description of
non-Gaussianity. However, a mild scale-dependence of fNL is natural. This
scale dependence is a new observable, potentially detectable with the
Planck satellite, which helps to further discriminate between models of
inflation. It is sensitive to properties of the early universe which are not probed by the standard observables. In a complementary way, the
trispectrum also contains important information about non-Gaussianity
which the bispectrum does not capture. Using simple models, I will
demonstrate how scale-dependence and the trispectrum provide a powerful
probe of the early universe. |
Oct 25 2011
16:00 |
SISSA, Room 005
|
Nils Andersson
(University of Southampton)
|
Neutron stars as cosmic laboratories |
ABSTRACT: Astrophysical observations have unveiled a veritable menagerie of neutron stars, associated with an exciting range of phenomena. Making sense of these observations, and extracting as much physics from them as possible, is an immense challenge. The ultimate aim is to understand the state of matter under the extreme conditions that prevail in these systems, but we are still quite far from reaching this target. The main aim of this talk is to introduce the main issues involved, discuss the constraints imposed by current observations (both using electromagnetic signals and gravitational waves) and highlight some of the key questions for the future. |
Oct 11 2011
16:00 |
SISSA, room 005
|
Roberto Maiolino
(INAF-OAR, Rome)
|
ALMA Prospects |
ABSTRACT: |
Jun 07 2011
16:00 |
SISSA, room 005
|
Sushan Konar
(Harish-Chandra Research Institute, Allahabad, India)
|
Millisecond Pulsars in Globular Clusters |
ABSTRACT: |
Apr 26 2011
16:00 |
SISSA, room 005
|
Brian Reville
(University of Oxford, UK)
|
Fermi acceleration at relativistic shocks and its radiative signatures |
ABSTRACT: |
Apr 12 2011
16:00 |
SISSA, room 005
|
Andrew King
(University of Leicester, UK)
|
Supermassive Black Holes in Galaxy Centres |
ABSTRACT: |
Mar 22 2011
16:00 |
SISSA, room 005
|
Pawel Haensel
(Nicolaus Copernicus Astronomical Center, Warsaw, Poland)
|
Two solar mass pulsar and hyperons in neutron star cores |
ABSTRACT: |
Mar 15 2011
16:00 |
SISSA, room 005
|
Mattia Negrello
(The Open University, Milton Keynes, UK)
|
Looking for strongly-lensed galaxies in the sub-mm with the Herschel Space Observatory |
ABSTRACT: It was first argued more than 10 years ago that wide-area surveys at submillimeter (and millimeter) wavelengths can potentially provide large (unbiased) samples of strongly lensed galaxies by taking advantage of a high magnification bias acting on the steep submillimeter source counts. However, it was not possible to test this theory before the advent of the Herschel Space Observatory, as prior sub-mm surveys were limited to small areas of the sky. The Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) represents the largest survey currently undertaken by Herschel and one of the scientific goals of H-ATLAS is the detection of a large number of gravitational lenses. I will describe the selection of the first gravitational lens candidates within the 14 square degrees field observed as part of the H-ATLAS during the Herschel Science Demonstration Phase. I will also discuss the properties of these objects and the campaign of follow-up
observations used to confirm their gravitational lensing nature. |
Mar 01 2011
16:00 |
SISSA, room 005
|
Jarrett Johnson
(Max-Planck-Institute for Extraterrestrial Physics, Munich, Germany)
|
Black Hole Formation in the Early Universe |
ABSTRACT: |
Nov 30 2010
16:00 |
SISSA, room 135
|
Lara Nava
(SISSA)
|
Gamma-Ray Bursts as standard candles: is it possible? |
ABSTRACT: Thanks to their huge luminosity, Gamma-Ray Bursts (GRBs) are detectable up to very high redshift (z=8.2 the present record holder). This characteristic makes GRBs very appealing for cosmological purposes, in particular, for the possibility to put some independent constraints on cosmological parameters. However, as for Supernovae Type Ia, GRBs are not characterised by a unique value of their luminosity/energetics. To overcome this problem, it has been proposed to use several empirical correlations between the energy/power of GRBs and their peak energy. Also these solutions, however, have their problems, such as the lack of low redshift calibrators, the large dispersion of several of these correlations, the lack of their theoretical interpretation and the still small number of objects. In this talk I will review the methods proposed to use GRBs as standard candles. I will discuss the advantages and the limitations of the correlations used to standardize GRB energetics, the present status and the future perspectives of constraining the cosmological parameters through GRBs. |
Nov 16 2010
16:00 |
SISSA, room 005
|
Silke Weinfurtner
(SISSA)
|
Measurement of stimulated Hawking emission in an analogue system |
ABSTRACT: There is a mathematical analogy between the propagation of fields in a general relativistic space-time and long (shallow water) surface waves on moving water. Hawking argued that black holes emit thermal radiation via a quantum spontaneous emission. Similar arguments predict the same effect near wave horizons in fluid flow. By placing a streamlined obstacle into an open channel flow we create a region of high velocity over the obstacle that can include wave horizons. Long waves propagating upstream towards this region are blocked and converted into short (deep water) waves. This is the analogue of the stimulated emission by a white hole (the time inverse of a black hole), and our measurements of the amplitudes of the converted waves demonstrate the thermal nature of the conversion process for this system. Given the close relationship between stimulated and spontaneous emission, our findings attest to the generality of the Hawking process. |
Nov 09 2010
16:00 |
SISSA, room 005
|
Luciano Rezzolla
(Albert Einstein Institute, Potsdam, Germany)
|
Using numerical relativity to explore fundamental physics and astrophysics |
ABSTRACT: |
Oct 26 2010
16:00 |
SISSA, room 005
|
Anna Bonaldi
(INAF, Astronomical Observatory in Padua)
|
Cosmic Microwave Background and Galactic foreground separation in CMB experiments |
ABSTRACT: |
Oct 05 2010
16:00 |
SISSA, room 005
|
Eugene Churazov
(MPA, Garching Germany)
|
Non-thermal pressure in early-type galaxies |
ABSTRACT: |
Jun 29 2010
16:00 |
SISSA, Room 135
|
Antony Valentini
(Imperial College, London, UK)
|
Beyond the Quantum |
ABSTRACT: According to hidden-variables theories, quantum physics is a special 'equilibrium' case of a much wider 'nonequilibrium' physics.
We describe the search for that wider physics in a cosmological context.
The hypothesis that the universe began in a state of quantum nonequilibrium is shown to have observable consequences.
In de Broglie-Bohm theory on expanding space, relaxation to quantum equilibrium is shown to be suppressed for field modes whose quantum time evolution satisfies a certain inequality, resulting in a 'freezing' of early nonequilibrium for these particular modes.
For an early radiation-dominated expansion, the inequality implies a corresponding physical wavelength that is larger than the (instantaneous) Hubble radius.
These results make it possible, for the first time, to make quantitative predictions for deviations from quantum theory.
We consider, in particular, corrections to inflationary predictions for the cosmic microwave background, and the possibility of finding relic cosmological particles that violate the laws of quantum mechanics.
(Reference: De Broglie-Bohm Prediction of Quantum Violations for Cosmological Super-Hubble Modes) |
Jun 22 2010
16:00 |
SISSA, Room 005
|
Luca Ciotti
(University of Bologna, Italy)
|
Clues on the formation of elliptical galaxies from their Scaling Laws |
ABSTRACT: I will review how the empirical galaxy scaling laws such as the Faber-Jackson, Fundamental Plane, Kormendy relations, when considered together with the Magorrian relation put strong constraints on the formation models of Elliptical Galaxies.
I'll also discuss the importance of AGN feedback. |
Jun 16 2010
16:00 |
SISSA, Room 135
|
Marco Baldi
(Max Planck Institute for Astrophysics, Garching, Germany)
|
N-body simulations of structure formation in the presence of dark interactions |
ABSTRACT: If the accelerated expansion of the Universe is driven by the dynamics of a classical scalar field, it is natural to speculate about possible interactions of such scalar field with other cosmic components as e.g. cold dark matter.
Interacting dark energy models have been widely studied in the last decade and have been shown to provide possible answers to the fine tuning problems of the standard LCDM cosmology. However, the effects of these models on observable structures have only recently started to be investigated, also by means of suitable modifications of N-body algorithms. I will discuss the impact that dark energy interactions, with constant or time dependent couplings, can have on large scale structures and on the properties of collapsed objects, as e.g. the baryonic fraction or the density profile of massive halos, from the outcomes of the first high-resolution hydrodynamical N-body simulations of interacting dark energy models. |
Jun 08 2010
16:00 |
SiSSA, Room TBD
|
Bruce Bassett
(SAAO, Cape Town, South Africa)
|
Baryon Acoustic Oscillations: review and future prospects |
ABSTRACT: We review the use of Baryon Acoustic Oscillations (BAO) as tools for cosmology focusing on simplifying the presentation of the basic physics as well as complications such as nonlinearity, survey design and statistical complications in the hunt for dark energy. |
Jun 01 2010
16:00 |
SiSSA, Room TBD
|
George Ellis
(University of Cape Town, South Africa)
|
Explaining the apparent acceleration of the universe: Lambda and multiverses, and inhomogeneous alternatives to dark energy |
ABSTRACT: |
Apr 27 2010
16:00 |
SISSA, Room D
|
Tess Jaffe
(CESR, Toulouse, France)
|
Modeling the Galactic Magnetic Field in the Plane |
ABSTRACT: |
Apr 13 2010
16:00 |
SISSA, Room D
|
Daniele Malesani
( Dark Cosmology Centre, Copenhagen, Denmark)
|
Gamma-ray bursts: a sample approach |
ABSTRACT: Gamma-ray bursts (GRBs) are bright explosions visible from all over the Universe. Being produced in core-collapse supernovae, they pinpoint environments where active star formation is ongoing. Spectroscopy of their optical counterparts (afterglows) allows to probe the medium of high-redshift galaxies, its gas content, metallicity, and dust extinction. GRBs also offer an effective way to locate high-redshift star-forming galaxies, selected in a way complementary to all other galaxy surveys. I will present an ongoing project to derive properties of GRB environments and host galaxies focussing on the need to collect a complete, well defined sample. The approach is twofold, starting from the immediate follow-up of GRB afterglows and continuing with late-time studies of GRB hosts. A special mention goes to the role of the now operational X-shooter instrument at the VLT, which will allow - and is in fact allowing - more detailed and effective GRB studies. |
Mar 23 2010
16:00 |
SISSA, Room D
|
Patrick Petitjean
(IAP, Paris, France)
|
Absorption line systems in quasars: from large scales to the ISM of high-z galaxies |
ABSTRACT: |
Mar 09 2010
16:00 |
SISSA, Room D
|
Luigi Stella
(INAF-Rome Astronomical Observatory)
|
An introduction to magnetars and some aspects of their physics |
ABSTRACT: |
Mar 02 2010
16:00 |
SISSA, Room D
|
Jens Niemeyer
(University of Goettingen, Germany)
|
The Evolution of Turbulence in the Intergalactic Medium |
ABSTRACT: |
Feb 09 2010
16:00 |
SISSA, Room D
|
Thomas Sotiriou
(DAMTP, Cambridge, UK)
|
Astrophysical Black Holes as Particle Colliders |
ABSTRACT: |
Feb 02 2010
16:00 |
SISSA, Room D
|
Enric Verdaguer
(University of Barcelona, Spain)
|
Cosmological perturbations in Semiclassical and Stochastic Gravity |
ABSTRACT: |
Oct 22 2009
16:00 |
SISSA, Room E
|
Luca Maccione
(Hamburg University)
|
Facts and perspectives towards understanding high energy cosmic ray propagation, and multidisciplinary applications |
ABSTRACT: |
Jun 23 2009
16:00 |
SISSA, Room D
|
Burkhard Zink
(Louisiana State University (US))
|
Oscillations of relativistic stars and disks |
ABSTRACT: |
Jun 09 2009
16:00 |
SISSA, Room D
|
Stephan Rosswog
(Jacobs University Bremen, Germany)
|
SPH calculations of compact-object binaries |
ABSTRACT: |
Jun 02 2009
16:00 |
SISSA, Room D
|
Vladimir Karas
(Charles University, Prague, Czech Republic)
|
Relativistic effects in spectra and polarisation from black hole accretion discs |
ABSTRACT: The inner parts of accretion flows onto black holes have been studied by means of X-ray spectroscopy. This effort aims to explore the extreme conditions of gaseous matter in cores of active galactic nuclei and close to compact components of binary stars. In particular, one would like to reveal signatures of strong gravitational fields in these objects. The overall spectral shape and various features are explained relatively well in terms of simplified models, but more sophistication will be needed in order to understand future time-resolved spectra at an enhanced level of future spectral and timing resolution, and to interpret new pieces of evidence, such as the polarimetric information. We summarize the equations describing light intensity and polarization propagation through plasmas in strong gravitational fields. |
Apr 28 2009
16:00 |
SISSA, Room D
|
Clive Dickinson
(Jodrell Bank, Manchester, UK)
|
Foreground cleaning and reconstruction in modern CMB experiments |
ABSTRACT: |
Mar 24 2009
16:00 |
SISSA, Room D
|
Sadegh Khochfar
(MPI for Extraterrestrial Physics, Munich, Germany)
|
The high-z Universe |
ABSTRACT: |
Mar 10 2009
16:00 |
SISSA, Room D
|
Alessandro Melchiorri
(Rome, University La Sapienza)
|
Future measurements of Cosmic Microwave Background Anisotropies as a test for fundamental physics |
ABSTRACT: In the next years new satellite, balloon-borne and ground based experiments will map temperature and polarization fluctuations in the cosmic microwave background (CMB) with unprecedented resolution and sensitivity. In this talk I will review the expected scientific impact of these measurements on several aspects of fundamental physics. |
