The joint DAUT-ICTP-OAT-SISSA colloquia are organised in collaboration with Andrea Biviano (OAT), Pierluigi Monaco (DAUT), Paolo Creminelli (ICTP) and take place both in Villa Bazzoni at the OAT/DAUT site, and at the SISSA/ICTP site.
Coming to give a seminar at SISSA ? Please refer to our seminar speaker's page.
There are no seminars scheduled for today.
Upcoming seminars:
| Time | Location | Type | Speaker | Title |
|---|---|---|---|---|
| Tue, Mar 23, 16:00 | SISSA, Room D | AC | Patrick Petitjean (IAP, Paris, France) | Absorption line systems in quasars: from large scales to the ISM of high-z galaxies |
| Tue, Mar 30, 16:00 | SISSA Main Building, Room D | AC | Enrica Iodice (INAF-Naples Astronomical Observatory) | New dynamical model for the polar disk galaxy NGC4650A: solving the enigma of the flattening of its dark halo NGC4650A is the prototype for the Polar Ring Galaxies (PRGs) and it is one of the best-investigated PRGs. The existence of two decoupled components of the angular momentum let PRGs the ideal laboratory i) to test gravitational interactions and merging and ii) to constrain the 3D shape of its dark matter halo. In view of these applications, I will briefly review the main results obtained on both research fields and, then, I will present the new dynamical model developed to derive the dark halo content and shape in NGC4650A, by using different dynamical traces (stars and gas) along the equatorial and meridian plane. |
| Wed, Mar 31, 13:00 | SISSA, Room E | JC | Rudy Gilmore (SISSA) | TBD |
| Tue, Apr 06, 16:00 | SISSA, Room D | AC | Jean-Philippe Uzan (IAP, Paris, France) | Testing General Relativity and Copernican Principle |
| Wed, Apr 07, 13:00 | SISSA Main Building, Room E | SS | Goffredo Chirco | TBD |
| Tue, Apr 13, 16:00 | SISSA Main Building, Room D | AC | Daniele Malesani (Dark Cosmology Centre, Copenhagen, Denmark) | Gamma-ray bursts: a sample approach 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. |
| Wed, Apr 14, 13:00 | SISSA Main Building, Room E | SS | Laura Bonavera | TBD |
| Tue, Apr 20, 16:00 | SISSA, Room D | AC | Joop Schaye (Leiden University, The Netherlands) | TBD |
| Wed, Apr 21, 13:00 | SISSA Main Building, Room E | SS | Lulu Fan | TBD |
| Tue, Apr 27, 16:00 | SISSA, Room D | AC | Tess Jaffe (CESR, Toulouse, France) | Modeling the Galactic Magnetic Field in the Plane |
| Wed, Apr 28, 13:00 | SISSA Main Building, Room E | SS | Alessandro Renzi | TBD |
| Tue, May 04, 16:00 | SISSA, Room D | AC | Phil Uttley (School of Physics & Astronomy University, Southampton, UK) | The voice of the accretion disc in accreting black holes |
| Wed, May 05, 13:00 | SISSA Main Building, Room E | SS | Antonella Garzilli | TBD |
| Tue, May 11, 16:00 | SISSA, Room D | AC | Martin Haehnelt (Institute of Astronomy, Cambridge, UK) | TBD |
| Wed, May 12, 13:00 | SISSA Main Building, Room E | SS | Stefano Finazzi | TBD |
| Thu, May 20, 15:00 | Villa Bazzoni, Conference Room | J | Martin Asplund (Max Planck Institut for Astrophysics di Garching) | Stellar emissions and evolution |
| Tue, May 25, 16:00 | SISSA, Room D | AC | Steve Eales (School of Physics and Astronomy, Cardiff University, UK) | The Herschel Surveys - what we have learned so far |
| Wed, May 26, 13:00 | SISSA Main Building, Room E | SS | Claudio Cremaschini | TBD |
| Tue, Jun 01, 16:00 | SISSA, Room D | AC | Eugene Churazov (MPA, Garching Germany) | TBD |
| Tue, Jun 08, 16:00 | SISSA, Room D | AC | Bruce Bassett (SAAO, Cape Town, Africa) | TBD |
| Wed, Jun 09, 13:00 | SISSA Main Building, Room E | SS | Yabebal Fantaye | TBD |
| Wed, Jun 16, 13:00 | SISSA Main Building, Room E | SS | Emilio Tejeda | TBD |
| Thu, Jun 17, 16:00 | SISSA, Room D | J | Sandro D'Odorico (ESO, Garching, Germany) | Science goals with the E-ELT: prospects from the instrumentation studies |
| Tue, Jun 22, 16:00 | SISSA, Room D | AC | Luca Ciotti (University of Bologna) | TBD |
| Wed, Jun 23, 13:00 | SISSA Main Building, Room E | SS | Nicola Bassan | TBD |
| Thu, Sep 16, 15:00 | INAF-OATs, Villa Bazzoni, Conference Room | J | Trevor Ponman (University of Birmingham, UK) | TBD |
| Thu, Nov 11, 16:00 | SISSA Main Building, Room D | AC | Luciano Rezzolla (Albert Einstein Institute, Potsdam, Germaany) | Using numerical relativity to explore fundamental physics and astrophysics |
Past seminars:
| Time | Location | Type | Speaker | Title |
|---|---|---|---|---|
| Wed, Feb 10 2010, 13:00 | SISSA, Room E | JC | Ana Babic (SISSA) | Supermassive black holes in disk galaxies I will review correlations of the black hole mass with the host galaxy properties, with an emphasis on the current status of disk galaxies. |
| Tue, Feb 09 2010, 16:00 | SISSA, Room D | AC | Thomas Sotiriou (DAMTP, Cambridge, UK) | Astrophysical Black Holes as Particle Colliders |
| Tue, Feb 02 2010, 16:00 | SISSA, Room D | AC | Enric Verdaguer (University of Barcelona, Spain) | Cosmological perturbations in Semiclassical and Stochastic Gravity |
| Wed, Jan 27 2010, 16:00 | SISSA, Room E | JC | Nicola Bassan (SISSA) | Neutron star crust microphysics and its relevant astrophysical effects Microphysics in neutron stars is thought to play a leading role in determining global behaviour of the whole object. Even some tiny quantum effects (like superfluidity) are thought to play a major role in describing observable astrophysical phenomena (like glitches). In my talk I will try to introduce the most relevant microphysics-related tools and to discuss their relevance for astrophysics and the questions that naturally arise when trying to bridge the gap between these two areas. |
| Tue, Jan 26 2010, 16:00 | SISSA, Room D | AC | Thomas Reiprich (Bonn University, Germany) | Galaxy Cluster Physics |
| Wed, Jan 13 2010, 13:00 | SISSA, Room D | JC | Wolfgang Kastaun (SISSA) | Nonlinear general relativistic hydrodynamics and I |
| Wed, Dec 16 2009, 16:00 | SISSA, Room E | IAS | Marcella Veneziani (University of Rome La Sapienza) | Cirrus clouds observed by BOOMERanG |
| Wed, Dec 02 2009, 13:00 | SISSA, Room D | JC | Saumyadip Samui (SISSA) | Cosmic ray driven galactic outflows Cosmic rays (CRs) are likely to be efficiently generated in supernova shocks in all galaxies including those at high redshift which are undergoing copious star formation. They could then aid in driving outflows from such galaxies. We obtain solutions of such CR driven free winds in a gravitational potential of the NFW form, relevant to galaxies. Cosmic rays naturally provide the extra energy and/or momentum input to the system, needed for a transonic wind solution in a gas with adiabatic index 5/3. We show that CRs can effectively drive winds even when the thermal energy of the gas is lost due to radiative cooling. These wind solutions predict an asymptotic wind speed closely related to the circular velocity of the galaxy. Furthermore, the mass outflow rate per unit star formation rate (eta_w) is predicted to be ~ 0.2-0.5 for massive galaxies. We show eta_w to be inversely proportional to the square of the circular velocity. A large eta_w for small mass galaxies implies that CR driven outflows could provide a strong negative feedback to the star formation in dwarf galaxies. These conclusions are applicable to the class of free wind models where the source region is confined to be within the sonic point. (Based on Samui, Subramanian, Srianand, arXiv:0909.3854). |
| Tue, Dec 01 2009, 16:00 | SISSA, Room D | AC | Alexander Zakharov (Institute of Theoretical and Experimental Physics, Moscow) | Exoplanet searches with microlensing |
| Thu, Nov 26 2009, 16:00 | SISSA, Room E | IAS | Alessio Recati (CNR-INFM BEC Center, Trento) | Bogoliubov Theory of acoustic Hawking radiation in Bose-Einstein Condensates We apply the microscopic Bogoliubov theory of dilute Bose-Einstein condensates to analyze quantum and thermal fluctuations in a flowing atomic condensate in the presence of a sonic horizon. For the simplest case of a step-like horizon, closed-form analytical expressions are found for the spectral distribution of the analog Hawking radiation and for the density correlation function. The peculiar long-distance density correlations that appear as a consequence of the Hawking emission features turns out to be reinforced by a finite initial temperature of the condensate. The analytical results are in good quantitative agreement with first principle numerical calculations. |
| Thu, Nov 19 2009, 15:00 | SISSA, Room E | IAS | Luis Jaramillo (AEI, Postdam, Germany) | Quasi-local black hole horizons: discussing the role of the observer We discuss the notion of a trapping or dynamical horizon as a quasi-local model for the horizon of a black hole in a dynamical regime, with a focus on the non-uniqueness properties of these objects. Originally motivated by the Cauchy construction of black hole spacetimes, our analysis will aim at setting the basic elements for a discussion of the possible implications of such "quasi-local horizon non-uniqueness" on black hole and spacetime thermodynamics. |
| Tue, Oct 27 2009, 14:00 | SISSA, Room D | AC | Spyros Kitsionas (Potsdam Institute, Germany) | SPH simulations of gravoturbulent fragmentation and cloud-cloud collisions In this talk, I will review the gravoturbulent fragmentation paradigm of star formation, in which (dispersing) supersonic turbulent gas motions and self-gravitational forces not only compete each other but also collaborate towards the formation of prestellar condensations that will collapse to form stars. I will present the numerical algorithms we employ for the study of such a complex physical system, namely the use of the Smoothed Particle Hydrodynamics code including a turbulent driver and particle splitting. I will discuss the relevance of our modelling of turbulence through a comprehensive comparison between the ability of various SPH and grid codes to model supersonic turbulence (Kitsionas et al. 2009). I will also argue for the ability of such a code to model gravitational fragmentation and collapse. In particular, I will present recent simulations of cloud collisions in the context of the turbulent ISM, using SPH with particle splitting (Kitsionas & Whitworth 2007). |
| Thu, Oct 22 2009, 16:00 | SISSA, Room E | AC | Luca Maccione ( Hamburg University, Germany) | Facts and perspectives towards understanding high energy cosmic ray propagation, and multidisciplinary applications |
| Fri, Oct 09 2009, 15:00 | SISSA, Room E | IAS | Jorge Moreno (Haverford College, Pennsylvania, USA) | Halo mergers, quasars and downsizing We propose a simple analytic model of active galactic nuclei (AGN) triggered by major mergers of dark matter haloes. The model consists of two main ingredients: (1) the halo merger rate as the main triggering agent, and (2) the quasar light curve, which describes the evolution of individual quasars. We use a theoretical merger rate compatible with cosmological simulations, and define major mergers as those with mass ratio of at least 1:3. The light curve has two components: an exponential ascending phase and a power-law descending phase that depends on mass of the host. We postulate a self-regulation condition between the peak luminosity and the mass of the host halo at triggering, and only massive hosts are considered. The descending phase is modeled such that AGN in more massive haloes shut down faster than in less massive ones. This is compatible with downsizing, since observations reveal little or no sign of recent star formation in massive early-type galaxies. Our results match the luminosity function, the quasar clustering, the local black hole mass function, and the Eddington-ratio distribution. We also explore the consequences of extending our model to include minor mergers, less massive hosts and massive black hole seeds. We make predictions for the local M-sigma relation and its redshift evolution. Lastly, we propose a simple evolutionary model where obscured sources only include the first portion of the light curve, while the rest describes optical AGN. |
| Tue, Oct 06 2009, 16:00 | SISSA, Room D | AC | Silke Weinfurtner (University of British Columbia, Canada) | Anisotropic scaling: From condensed matter systems to Horava-Lifshitz gravity Horava-Lifshitz gravity is based on the assumption of anisotropic scaling of space and time. Presently the situation at hand is on shaky grounds as we are lacking any rigourous loop calculations for Horava-Lifshitz gravity. However, we will demonstrate the very idea of anisotropic scaling is a nature inspired concept arising in all quantum field theories involving an emergent (or induced) spacetime geometry. We will show that for a certain degree of anisotropy it is indeed possible to use anisotropic scaling as a quantum field theory regulator for an arbitrarily interacting (massive or massless) scalar field. Inspired from this well understood quantum field theory we will show how to map the concept of anisotropic scaling onto gravity; and in this sense onto any field theory. |
| Thu, Oct 01 2009, 16:00 | SISSA, Room E | IAS | Renaud Parentani (LPT, Orsay, France) | Black Hole radiation in Bose Einstein condensates We study the phonon fluxes when the condensate velocity crosses the speed of sound, i.e., in backgrounds which are analogue to that of a black hole. Our theoretical analysis and numerical results are based on the Bogoliubov-de Gennes equation without any further approximation. The spectral properties of the fluxes and of the long distance density- density correlations are obtained, with and without an initial temperature. In realistic conditions, the condensate temperature dominates the fluxes, and thus hides the Hawking effect, but it amplifies the long distance correlations which are intrinsic to this effect. This confirms that the correlations pattern offers a neat signature of the Hawking effect. Optimal conditions to observe the pattern are discussed. Fluxes associated with white holes are also discussed. |
| Thu, Sep 24 2009, 11:00 | SISSA, Room E | IAS | Shigehiro Nagataki (Yukawa University) | GRB-SN Connection: Central Engine of Long GRBs and Explosive Nucleosynthesis |
| Tue, Sep 15 2009, 16:00 | SISSA, Room E | AC | Christian Ott (Caltech) | Probing the Mechanism of Core-Collapse Supernovae with Gravitational Waves |
| Mon, Sep 14 2009, 16:00 | SISSA, Room D | IAS | Smita Mathur (Ohio State) | Chandra to IXO |
| Thu, Jul 23 2009, 10:00 | SISSA, Room E | IAS | Francesco Marino (University of Florence) | Rotating acoustic black holes and superradiance in a nonlinear optical cavity Exploiting the relation between nonlinear optics and fluid dynamics we show that rotating acoustic black holes can be created in a self- defocusing optical cavity. Light-matter interaction in self- defocusing media can be indeed described in terms of a two-dimensional 'photon-fluid' on which linear excitations (sound-waves) experience an effective Lorentzian curved spacetime determined by the physical properties of the flow. Since in an optical cavity configuration the background flow is 'pinned' by the driving field, the injection of a suitable optical vortex beam allows the generation of acoustic ergoregions and event horizons. An experiment to simulate the Kerr geometry and observe superradiance is proposed. |
| Thu, Jul 16 2009, 16:00 | SISSA, Room D | IAS | Thomas Sotiriou (DAMTP, Cambridge, UK) | Destroying a black hole with test particles
As is well known, the horizon hiding the singularity in a Kerr black hole is present only if the mass M and the angular momentum J satisfy the relation J= |
| Tue, Jul 07 2009, 16:00 | SISSA, Room D | IAS | Lara Nava (INAF - Brera Astronomical Observatory) | Gamma-Ray Bursts: theory and observations |
| Thu, Jun 25 2009, 16:00 | SISSA, Room E | IAS | Valerio Faraoni (Bishop University, Canada) | Cosmological expansion and local dynamics Assuming that the Friedmann metric is valid down to small scales, do local objects expand with the universe or resist the expansion? This long-standing issue will be revisited with the help of new exact solutions describing black holes embedded in cosmological backgrounds. Apart from the (static) de Sitter background, even the most strongly bound object, the black hole, participates in the expansion of the cosmic substratum. Issues of interpretation and genericity of the new exact solutions will be discussed. |
| Tue, Jun 23 2009, 16:00 | SISSA, Room D | AC | Burkhard Zink (Albert Einstein Institute, Berlin, Germany) | Oscillations of relativistic stars and disks |
| Wed, Jun 10 2009, 14:30 | SISSA, Room E | SS | Lulu Fan (SISSA) | The role of the QSOs feedback in the dramatic size evolution of ETGs Observations have evidenced that passively evolving massive galaxies at high redshift are much more compact than local galaxies with the same stellar mass. We argue that the observed strong evolution in size is directly related to the quasar feedback, which removes huge amounts of cold gas from the central regions in a Salpeter time, inducing an expansion of the stellar distribution. The new equilibrium configuration, with a size increased by a factor >~ 3, is attained after ~ 40 dynamical times, corresponding to ~ 2 Gyr. This means that massive galaxies observed at z >~ 1 will settle on the Fundamental Plane by z ~ 0.8-1. In less massive galaxies (M_star <~ 2 1010 M_sun), the nuclear feedback is subdominant, and the mass loss is mainly due to stellar winds. In this case, the mass loss timescale is longer than the dynamical time and results in adiabatic expansion that may increase the effective radius by a factor of up to ~ 2 in 10 Gyr, although a growth by a factor of ~ 1.6 occurs within the first 0.5 Gyr. Since observations are focused on relatively old galaxies, with ages >~ 1 Gyr, the evolution for smaller galaxies is more difficult to perceive. Significant evolution of velocity dispersion is predicted for both small and large galaxies. |
| Tue, Jun 09 2009, 16:00 | SISSA, Room D | AC | Stephan Rosswog (Jacobs University Bremen, Germany) | Atypical supernovae from the tidal crushing of white dwarfs by black holes |
| Thu, Jun 04 2009, 15:00 | SISSA, Room D | AC | Vladimir Karas (Charles University, Prague) | Relativistic effects in spectra and polarisation from black hole accretion discs 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. |
| Wed, Jun 03 2009, 14:30 | SISSA, Room E | SS | Giulia Migliori (SISSA) | X-ray emission from GPS and CSS sources: constraints on the extended component GhigaHertz Peaked Spectrum (GPS) and Compact Steep Spectrum (CSS) sources are compact and powerful radio sources, most likely observed at the early stage of their growth. Theoretical predictions expect X-ray emission coming from both the evolving radio source itself and the intergalatic/intracluster medium heated up during the source expansion. Over the last few years many X-ray observations of GPS/CSSs have been successfully performed with Chandra and XMM-Newton observatories. Nevertheless, due to the observational limits the origin of the observed X-ray emission is still matter of debate. In my talk, I will discuss the possibility to put some constraints on the X-ray emission related to GPS/CSS extended components, namely jets, hot spots and lobes, referring to the paradigmatic case of the CSS quasar 3C 186 and define the conditions under which it is possible to fully ascribe the X-ray emission of 3C 186 to the extended components. In the second part, the radio loudness excess displayed by some of these compact radio sources is analyzed in the frame of the models for the radio power evolution. Finally, I will briefly consider the futureperspectives for GPS/CSS observations with FERMI/GLAST satellite. |
| Tue, May 26 2009, 15:00 | SISSA, Room E | SS | Pratika Dayal (SISSA) | Lyman Alpha Emitters Through Reionization The present talk will focus on recently obtained results concerning the nature andproperties of Lyman Alpha Emitters (LAEs) and their use as a probe to investigate cosmic reionization history. Based on state-of-art hydrodynamical simulations we discuss how the LAE Lya luminosity functions observed at various redshifts might be affected by the presence of intergalactic neutral gas and clarify the role of dust grains and clustering of sources. For the first time a coherent picture is developed in which the nature and global properties (stellar mass, star formation rate, metallicity, gas mass and temperature) of the emitters are linked to their visibility. We also test our model by reproducing the SED of specific high-z LAEs, as observed by Lai et al. 2007, for which Spitzer data are available. I will discuss the remaining puzzles and possible strategies to overcome them. |
| Thu, May 21 2009, 16:00 | Villa Bazzoni, Conference Room | J | George Miley (Leiden Observatory, The Netherlands) | Probing the Early Universe with Radio Galaxies |
| Wed, May 20 2009, 14:30 | SISSA, Room E | SS | Goffredo Chirco (SISSA) | From black hole to spacetime thermodynamics: the Einstein equation as a spacetime equation of state, in a non-equilibrium setting Starting from a brief overview on the connection between gravity, quantum field theory and thermodynamics, I will show how the thermodynamical description of black hole mechanics can be extended to the entire spacetime, given the thermal character of quantum spacetime at macroscopic level and the stationarity properties of local causal horizons. In this setting, I will show how the Einstein equation can be derived from a local thermodynamical equilibrium assumption, as a constitutive equation for the spacetime. In particular I will argue on the possibility to recover the Einstein equation of state from a non-equilibrium thermodynamics, where some intrinsic spacetime viscosity come into the play, apparently related to the purely gravitational degrees of freedom. |
| Tue, May 19 2009, 11:00 | SISSA, Room E | B | Carlo Baccigalupi (SISSA) | TBD |
| Wed, May 13 2009, 14:30 | SISSA, Room E | SS | Carmelo Evoli (SISSA) | The turbulent intergalactic medium I will present new results concerning supernova-driven outflows as a mechanism to pump and sustain turbulence in the IGM surrounding high-redshift galaxies. The evolution of winds is investigated via a semi-analytic approach following both galaxy evolution along its hierarchical growth and the expansion of supernova driven superbubbles as they escape from the halo potential well. We investigate the turbulence evolution within the bubble using a novel approach based on the spectral transfer equation. In brief, this approach allows to follow the turbulent energy density deposite by galactic winds in the IGM, its spectral features, dissipation, and to predict the corresponding thermal/kinetic properties of such component. Preliminary results will be presented showing the contribution of turbulent pressure to QSO line-of-sights passing nearby UV-selected galaxies at redshift 1.8 < z < 3.3. |
| Thu, May 07 2009, 16:00 | SISSA, Room E | IAS | David Rapetti (SLAC, Stanford, USA) | Constraints on dark energy and modified gravity from X-ray luminous galaxy clusters Using two complementary X-ray galaxy cluster studies we present new constraints on dark energy and modified gravity models. Using Chandra measurements of the X-ray gas mass fraction (fgas) in 42 massive, relaxed galaxy clusters we obtain a tight constraint on the mean matter density, Omega_m, and a detection of the effects of dark energy comparable in significance to recent type Ia supernovae (SNIa) studies. We also find that fgas measurements from a future X-ray observatory can be used to provide comparable constraints on dark energy to those predicted by the Dark Energy Task Force for other leading, planned dark energy experiments. Furthermore, using fgas and SNIa data we measure key kinematical parameters of the expansion history of the Universe such as the dimensionless second and third derivatives of the scale factor with respect to cosmic time, which are independent of any dynamical, i.e. gravity, model. Our results provide further support for the concordance LCDM paradigm. Complementarily, we employ measurements of the evolution of the X-ray luminosity function of galaxy clusters to determine both the dark energy equation of state, w, and the growth index, gamma. We use the later to parameterize the growth rate as Omega_m(z)^gamma, for which General Relativity (GR) predicts gamma~0.55. Using conservative allowances for systematic uncertainties, we find gamma=0.51+0.16-0.15 (68.3 per cent confidence limits), for a flat LCDM background model. We find no evidence for departures from GR on large scales. |
| Wed, May 06 2009, 14:30 | SISSA, Room E | SS | Laura Bonavera (SISSA) | Small Scale Cosmic Microwave Background Anisotropy: Unresolved Sources and Cosmic Infrared Background The importance of the Cosmic Infrared Background (CIB) is two fold: on one hand it has a great scientific importance itself, on the other hand, at microwave frequencies the fluctuations generated by undetected sources contaminate the CMB anisotropies. So far, no component separation method succeeded in extracting the CIB from simulated Planck maps. It is therefore necessary to develop specific methods. |
| Tue, May 05 2009, 16:00 | SISSA, Room D | AC | Paul Taylor (Cape Town University, South Africa) | Understanding long gamma-ray bursts |
| Tue, Apr 28 2009, 14:15 | SISSA, Room D | AC | Clive Dickinson (Jodrell Bank, Manchester, UK) | Foregrounds: Friend or Foe |
| Wed, Apr 22 2009, 16:00 | SISSA, Room E | SS | Stefano Finazzi (SISSA) | Analogue Models of Gravity and Superluminal Travel The motivation for studying analogue models of gravity is twofold. Firstly, phenomena as Hawking radiation are very faint in ordinary gravity. The realization of analogue systems as Bose-Einstein condensates can be the only way to probe experimentally some prediction of quantum field theory in curved spacetimes. Secondly, analogue models suggest different theoretical approaches to quantum gravity phenomenology. Furthermore, as a by-product, the instruments developed to study these systems can be used to solve open problems of general relativity and quantum field theory. As an example, I will show this machinery at work to put constraints on the possibility of superluminal travel through the Alcubierre's warp drive. |
| Thu, Apr 16 2009, 16:00 | Conference Room, ICTP Main Building | J | Georgi Dvali (New York University, USA) | Black holes and the origin of species |
| Tue, Mar 24 2009, 16:00 | SISSA, Room D | AC | Sadegh Khochfar (Max-Planck Institute for Extraterrestrial Physics, Munich) | The high-z Universe |
| Thu, Mar 19 2009, 16:00 | SISSA, Room D | J | Alessandro Bressan (INAF - Astronomical Observatory in Padua) | Recent advances in Stellar Evolution and interplay with Galaxy formation |
| Wed, Mar 11 2009, 14:30 | SISSA, Room E | JC | Eunhwa Jeong (SISSA) | Non-Gaussianity as a Probe of the Physics of the Primordial Universe and the Astrophysics of the Low Redshift Universe (Komatsu el al '09); B-mode Detection with an Extended Planck Mission (Efstathiou and Gratton '09) |
| Tue, Mar 10 2009, 16:00 | SISSA, Room D | AC | Alessandro Melchiorri (Rome University La Sapienza) | Future measurements of Cosmic Microwave Background Anisotropies as a test for fundamental physics 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. |
| Wed, Mar 04 2009, 16:00 | SISSA, Room E | IAS | Mariangela Bernardi (University of Pennsylvania, Philadelphia, USA) | Massive galaxies in massive datasets Understanding why massive early-type galaxies are red and dead has proved to be difficult. This has been the source of tension with hierarchical formation models, such as the Cold Dark Matter model, in which massive objects are formed from mergers of smaller ones which existed at early times. The problem is to arrange for star formation to occur at higher redshift than the actual assembly of the stars into a single massive galaxy. The most recent galaxy formation models arrange for this to happen by a combination of two processes: dry mergers and AGN feedback. I will discuss a number of results on massive galaxy formation that are based on analyses of Brightest Cluster Galaxies and other extreme objects in the SDSS and other recent astrophysical datasets. |
| Wed, Feb 25 2009, 14:30 | SISSA, Room E | JC | Carlo Baccigalupi (SISSA) | What the small angle CMB really tells us about the curvature of the Universe - Clifton T. et al (2009) |
| Tue, Feb 10 2009, 16:00 | SISSA, Room D | AC | Thomas Konopka (Perimeter Institute, Canada) | Graphs and emergent spacetimes |
| Wed, Feb 04 2009, 14:30 | SISSA, Room E | JC | Francisco Shu Kitaura | Cosmic Cartography of the Large Scale Structure We discuss the problem of 3-D matter field reconstructions based on galaxy redshift surveys and show recent results based on the Sloan Digital Sky Survey |
| Thu, Jan 29 2009, 16:00 | SISSA, Room E | IAS | Elena Gallo (MIT Kavli Institute for Astrophysics and Space Research, Cambridge, MA, USA) | Low-luminosity accreting black holes in the nearby Universe |
| Wed, Jan 28 2009, 14:30 | SISSA, Room E | JC | Sam Leach (SISSA) | Discussion of ARCADE 2 results (Kogut el al 2009) |
| Thu, Jan 22 2009, 16:00 | SISSA, Room E | IAS | Matthew Francis (Institute of Astronomy, University of Sydney, New South Wales, Australia) | Can early dark energy be detected in non-linear structure formation? In most dark energy scenarios, including the standard cosmological constant case, dark energy becomes important only late in the Universe's history. However, plausible physical models exist that predict a non- negligable presence of dark energy even at early times. Such 'early dark energy' has been shown to be capable of hiding in, and biasing, existing data making its presence hard to detect. In this talk I will detail recent work on assessing the effect of early dark energy on non-linear tructure through N-body simulations and semi-analytic theory. We find that early dark energy is difficult to detect in non-linear structure at low redshift, a finding in contrast to some previous work. Reasons for this difference will be discussed as well as suggestions for the optimal methods to search for early dark energy. |
| Wed, Jan 21 2009, 14:30 | SISSA, Room E | JC | Jason Dick (SISSA) | Discussion of Albrecht et al (2009) arXiv:0901.0721 |
| Tue, Jan 20 2009, 16:30 | SISSA, Room D | AC | Marco Bruni (Portsmouth University, UK) | Cosmology with a linear 2-parameters equation of state for the dark sector In this talk I describe recent work on cosmological models with a dark component parametrized by an "affine" equation of state (EoS) P=P_0+alpha rho. This phenomenological EoS can describe a dark barotropic fluid, but can also correspond to either a quintessence or a k-essence scalar field. In all cases, the affine EoS implies the existence of an effective cosmological constant. This dark component can either play the role of a Unified Dark Matter (UDM), or Dark Energy (DE). In the latter case, it is assumed that a standard Cold Dark Matter (CDM) component is also present. In addition, in this purely phenomenological framework, one is free to choose the effective speed of sound of perturbation to correspond to three subcases: 1) barotropic/k-essence, 2) quintessence scalar field, 3) zero speed of sound. For each of the UDM and the DE + CDM cases, and for each subcase, I will describe constrains on this class of models from the WMAP5 (CMB) and the SDSS (galaxy surveys) data. Perhaps the main conclusion is that while we don't yet know enough about the details of the late cosmological acceleration, CMB data and the matter power spectrum imply that there is very little space for modifications of the standard cosmological model, which includes a CDM component, at early times. |
| Wed, Jan 14 2009, 14:00 | SISSA, Room E | JC | Olivier Tiret (SISSA/ISAS, Trieste) | Galactic dynamics with modified gravity Dynamics of gravitational systems are traditionally based on Newtonian physics. At galactic scale, Newtonian gravity requires the existence of dark matter. Nowadays, this matter is invisible. If this model (LCDM) is successful at large scales, some difficulties appear at galactic scale. I use numerical simulations to explore an alternative to the Newtonian gravity: MOND, where the modification of the gravity follows an acceleration scaling law, without invoking any dark matter. This gravity is non-linear and needs more sophisticated methods than those which are used for Newtonian gravity with dark matter. |
| Tue, Jan 13 2009, 16:00 | SISSA, Room D | AC | Anze Slozar (University of California Berkeley, USA) | Primordial local non-Gaussianity and its contemporary probes Primordial non-Gaussianity has recently received a renewed attention. There are three main reasons for this. First, there is a claimed detection at nearly three sigma from the WMAP3 data in the literature. Second, a new method for constraining non-Gaussianity from the statistics of the large scale structure in the present universe has been found. Third, it has recently become clear that non-Gaussianity is one of the best probes of exotic models of inflation and its alternatives. I will review these recent advances in the field and then present our own constraints on the local non-Gaussianity parameter f_NL. I will conclude by discussing promising advances in methodology and prospects for the future detections. |
| Thu, Jan 08 2009, 16:00 | SISSA, Room D | IAS | Edvige Corbelli (INAF - Astronomical Observatory in Arcetri, Florence) | Star formation in nearby galaxies and the cluster birthline Nearby galaxies are ideal laboratories for studying the gas to star conversion process: from the intergalactic gas accretion phase to the formation of molecular clouds and of stellar clusters. Sensitive survey of HI emission around galaxies have recently found faint HI clouds, likely fueling star formation. Space observatories such as Spitzer, HST, GALEX have allowed to link large scale galaxy properties to those of individual star forming sites. The talk will summarize the most recent results on star formation in nearby galaxies and outline the importance of picturing bright HII regions as well as dim candles for understanding some basic properties of cluster formation. To this purpose the concept of cluster birthline will be introduced and tested in M33. |
| Tue, Dec 16 2008, 16:00 | SISSA, Room D | AC | Viviana Acquaviva (Princeton University, New Jersey, USA) | Testing Gravity with Redshift Galaxy Surveys |
| Mon, Dec 15 2008, 16:00 | SISSA, Room D | IAS | Tommaso Treu (University of California Santa Barbara, USA) | Supermassive black holes and galaxy evolution |
| Tue, Dec 02 2008, 16:00 | SISSA, Room E | AC | Sergei Popov (Sternberg Institute, Moscow) | Population synthesis of close-by cooling neutron stars |
| Thu, Nov 27 2008, 16:00 | SISSA, Room E | IAS | Serena Fagnocchi (University of Bologna, Italy) | Acoustic Black Holes and the Correlations of Hawking Radiation Hawking radiation is the most famous and elusive prediction related to the formation of a black hole. Widely considered a milestone of modern theoretical physics, so far no experiment is confirming its existence. More fundamental than the theory it has been first derived, Hawking radiation has been extended to any system able to reproduce the geometrical features of a forming black hole specetime: for example in supersonic flowing fluids the sound gets trapped exactly as light in a black hole. Such supersonic flow configurations are called "acoustic black holes" and can be used as laboratory to test gravitational effects otherwise undetectable (as Hawking radiation). It has been recently proposed how a clear signature of the presence of Hawking radiation in acoustic black holes appears in the density correlation pattern, analytically obtained using the formal analogy between gravitation and hydrodynamics, and numerically confirmed in an analysis able to take into account the full microscopic structure of the system. In this seminar the main features of the analogy between gravitation and hydrodynamics are reviewed. Then the peculiar correlation pattern associated to Hawking radiation is showed, stressing about its importance to reveal it in near future experiments. |
| Tue, Nov 25 2008, 13:30 | SISSA, Room D | AC | Christopher Eling (Racah Institute of Physics, Hebrew University of Jerusalem) | Hydrodynamics of spacetime and vacuum viscosity Recent work has shown that spacetime dynamics can be deduced from the non-equilbrium thermodynamics of all local causal horizons. In particular, by postulating an entropy balance law dS = dQ/T + d_i S connecting notions of horizon entropy, heat flux, temperature, and entropy production one can derive the Einstein equation. In this talk I will describe how this derivation can be reformulated in the language of hydrodynamics. I will argue that the vacuum thermal state ("thermal atmosphere") outside a local causal horizon can be treated as a fluid. The entropy balance law and Einstein equation then follow as a consequence of hydrodynamics. Interestingly, horizon fluid has universal properties: its entropy density is the Bekenstein-Hawking density and its shear viscosity to entropy density ratio is \hbar/4\pi. The \hbar/4\pi ratio also arises in gauge theory/gravity dualities, where it has received considerable attention recently. I will describe a possible relationship between the two pictures and discuss open questions. |
| Thu, Nov 20 2008, 16:00 | Villa Bazzoni, Conference Room | J | Nick Gnedin (Chicago University, USA) | Cosmological Reionization |
| Tue, Nov 11 2008, 16:00 | SISSA, Room D | AC | Vincenzo Cardone (University of Catania, Italy) | Cosmography of f(R) gravity |
| Tue, Oct 14 2008, 16:00 | SISSA, Room D | AC | Brice Menard (CITA, Toronto, Canada) | Gravitational lensing in the era of large surveys Observational cosmology has dramatically matured over the past decade, revealing the distribution of dark matter and constraining cosmological parameters to an unprecedented accuracy. In this quest, gravitational lensing has been an invaluable tool. I will briefly review the impact of gravitational lensing on cosmology, from the discovery of giant arcs to the recent detection of lensing of the Cosmic Microwave Background. I will then present two series of new results obtained with the SDSS: (i) the detection of the systematic magnification of quasars by galaxies, which can be used to map the distribution of dark matter up to cosmological scales; (ii) the first detection of sub-micron size particles (called dust) on large scales around galaxies. While such a result is of interest for the study of galaxy evolution, it has also direct implications for dark energy measurements using supernovae since intergalactic dust gives rise to extinction effects on background sources. I will discuss this new challenge and propose potential solutions for future dark energy experiments with upcoming surveys. |
| Thu, Sep 18 2008, 16:00 | Villa Bazzoni, Conference Room | J | Tim de Zeeuw (ESO, Munich, Germany) | The SAURON Survey |
| Thu, Sep 04 2008, 16:00 | SISSA, Room E | IAS | Sudipta Sarkar (IUCAA, Pune, India) | Thermodynamic Route to Field Equations in gravity Spacetimes with horizons show a resemblance to thermodynamic systems and one can associate the notions of temperature and entropy with them. In the case of Einstein-Hilbert gravity, it is possible to interpret Einstein's equations as the thermodynamic identity TdS = dE + PdV for a spherically symmetric spacetime and thus provide a thermodynamic route to understand the dynamics of gravity. We study this approach further and show that the field equations for Lanczos-Lovelock action in a spherically symmetric spacetime can also be expressed as TdS = dE + PdV with S and E being given by expressions previously derived in the literature by other approaches. The Lanczos-Lovelock Lagrangians are of the form L=Q_a^{bcd}R^a_{bcd} with \nabla_b Q^{abcd}=0. In such models, the expansion of Q^{abcd} in terms of the derivatives of the metric tensor determines the structure of the theory and higher order terms can be interpreted quantum corrections to Einstein gravity. These results are further generalized for Axis symmetric and time dependent horizons also. Our approach indicates a deep connection between the thermodynamics of horizons and the allowed quantum corrections to standard Einstein gravity, and shows that the relation TdS = dE + PdV has a greater domain of validity that Einstein's field equations. |
| Tue, Sep 02 2008, 16:00 | SISSA, Room D | AC | Renaud Parentani (University of Paris Sud, France) | Signatures of trans-Planckian dispersion in inflationary spectra The primordial spectra are calculated using dispersion relations which deviate from the relativistic one above a certain energy scale Lambda. We determine the properties of the leading modifications with respect to the standard spectra when Lambda is much greater than H, the Hubble scale during inflation. From deviations computed in de Sitter space, we algebraically deduce the modifications of scalar and tensor power spectra in slow roll inflation. The modifications do not exhibit oscillations unless the dispersion relation induces some non-adiabaticity near a given scale. Finally, we explore the regime where H and Lambda are comparable. Our results indicate that the project of reconstructing the inflaton potential cannot be pursued without making hypothesis about the dispersion relation of the fluctuation modes, see arXiv:0804.1920 for details. |
| Tue, Jul 15 2008, 16:00 | SISSA, Room D | AC | Francisco Shu-Kitaura (MPA Garching) | Joint density and power-spectrum reconstruction from a galaxy survey We present a novel method which jointly recovers the power-spectrum and the density field from a galaxy distribution. Our scheme explodes the phase information encoded in the density field to solve for the mode-coupling introduced by the selection function and mask. We test this on mock galaxy catalogues and show that the power-spectrum is reconstructed to great accuracy even for the lowest modes. |
| Thu, Jul 10 2008, 14:00 | SISSA, Room E | IAS | Martin Huarte-Espinosa (Mullard Radio Astronomical Observatory, Cambridge, UK) | The dynamical, MHD and chemical effects of FR II radio sources on the ICM and its magnetic fields. The feedback between the intra-cluster medium (ICM) and the active galaxy in the cores of galaxy clusters is evident when combining X-ray and radio observations. Numerical simulations permit to study the mutual evolution of these systems in detail by putting together information from observations and analytical models. In this presentation the dynamical, MHD and chemical effects of FR II radio sources on the ICM and its magnetic fields are described, along with two simulation in this context. I will show our models of the evolution of the metals in the ICM of a cool core cluster; from the continuous metal formation at the central galaxy, to their advection away from the cluster's core due to the effects of powerful intermittent jets. On the other hand, we simulate the magnetic fields in galaxy clusters with a spatial spectrum structure and random phases. I will talk about the synthetic rotation measure maps we do with these magnetised clusters and about our 3DMHD simulations of radio source feedback on these magnetic fields. |
| Wed, Jul 09 2008, 14:00 | SISSA, Room E | IAS | Brice Menard (CITA, Toronto, Canada) | Probing the distributions of dark matter, gas and dust around galaxies using the SDSS |
| Tue, Jul 08 2008, 16:00 | SISSA, Room D | AC | Valerio Faraoni (Physics Department Bishop's University, Canada) | f(R) gravity: successes and challenges `Modified'' of ``f(R)'' gravity has recently been revived as an alternative to dark energy to explain the present acceleration of the universe. The theory comes in three versions: metric, Palatini, and metric-affine. The successes of, and challenges for, f(R) gravity will be reviewed, with some emphasis on stability issues, the Cauchy problem, and successful scenarios. |
| Tue, Jul 01 2008, 16:00 | SISSA, Room E | AC | Jameel-Un Nabi (GIK Institute, Pakistan & ICTP) | Towards a better understanding of nuclear weak processes in massive stars Abstract: I will be discussing the role of nuclear weak processes in the course of evolution of massive stars. After a brief introduction to these processes I will be presenting few of my microscopic calculations of weak interaction rates in stellar matter and discuss their possible implications on the dynamics of core-collapse. |
| Thu, Jun 26 2008, 16:00 | SISSA, Room E | SS | Carmelo Evoli (SISSA) | The puzzling origin of the 6Li plateau The 6Li abundances observed in metal-poor halo stars (MPHSs) exhibit a metallicity plateau at [6Li/H] = -11.2. However, standard BBN models coupled with WMAP5 cosmological parameters predict a 6Li abundance about 1000 times smaller. A promising mechanism is the production of 6Li by spallation of cosmological cosmic rays (CCR) accelerated by supernovae (SNe) during the early formation of the Milky Way. In fact, 6Li can be synthesized after the BBN epoch by fusion reactions (alpha+alpha -> 6Li), when high-energy cosmic ray particles collide with ambient gas particles. Starting from a recent model of Milky Way (MW) evolution we follow the star formation and supernova history, and the chemical enrichment of the MW throughout its hierarchical merger tree, matching simultaneously several of the observed properties of the MW, and the Metallicity Distribution Function (MDF) of Galactic halo stars. We then study the resulting nucleosynthesis if most of the cosmic-rays produced were injected from Galactic substructures in which SNe exploded and escaped into the galactic medium (GM) interacting with He nuclei. We find that realistic and properly constrained models of Galaxy evolution can hardly explain the observed value of 6Li abundance and, in particular, cannot account for the observed 6Li flat metallicity distribution. Thus, it seems that to explain the observed plateau it is necessary to invoke a pre-galactic 6Li production by some yet unknown mechanism. |
| Fri, Jun 20 2008, 14:45 | SISSA, Room E | IAS | Thomas Sotiriou (University of Maryland) | Gravity Theories: From principles to practice Motivated by the recent stimulus in alternative theories of gravity, I discuss the long-standing issue of pinpointing the fundamental principles which the gravitational interaction needs to follow. Even though such principles do exist and are well known, their practical use becomes limited due to the serious difficulties that come about when one tries to formulate them mathematically. This highlights the problems related to having multiple representations of a theory. |
| Fri, Jun 20 2008, 14:15 | SISSA, Room E | IAS | Silke Weinfurtner (University of British Columbia) | Physical existence of signature change events and consequences of an absolute time in emergent spacetimes from Bose gas hydrodynamics. We present an example of emergent spacetime as the hydrodynamic limit of a more fundamental microscopic theory. This system naturally exhibits a microscopic mechanism allowing us to perform controlled signature change between Lorentzian and Riemannian geometries. We investigate the interplay between the underlying microscopic structure and the emergent gravitational field; in general, this can be thought of as the combination of trans-Planckian physics and signature-change physics. |
| Thu, Jun 19 2008, 16:00 | Villa Bazzoni, Conference Room | J | Scott Tremaine (Princeton university, New Jersey, USA) | Dynamics of planetary and stellar systems |
| Thu, Jun 12 2008, 16:00 | SISSA, Room E | SS | Luca Naso (SISSA) | Magnetic fields in accretion discs around neutron stars Magnetic fields play an important role in systems of accretion discs around neutron stars. One of the major effects is related to the appearence of a magnetic torque that, in higly magnetized objects or in the very inner regions of the disc, can overwhelm the viscous torque and become the main carrier of angular momentum. One of the consequences of this is the dependece of rotation of the central object on the structure of the magnetic field. However up to now, in all the works devoted to the calculation of the spin history of a neutron star, an ``ad hoc'' magnetic field profile has been used. We propose a strategy for a rigorous calculation of the magnetic field for a simple model of accretion. We consider a thin Keplerian disc (standard alpha disc), a neutron star with a dipolar magnetic field and, by supposing axisymmetry, we look for a stationary solution of the induction equation plus the equation of motion. Preliminary results seem to show a different solution from the standard one (according to which the toroidal component of the magnetic field is proportional to the relative angular velocity between the disc and the star) and also a surprising behaviour for the poloidal field. |
| Thu, Jun 05 2008, 16:00 | SISSA, Room E | SS | Marco Nardini (SISSA) | Rest frame properties of long GRB afterglows The study of the rest frame properties of long Gamma-Ray bursts (GRBs) afterglows is a fundamental aspect for a better understanding of the nature of these powerful explosions. The launch of the Swift satellite had been accompanied by a strong improvement of the observational capabilities especially for what concerns X-Rays and optical afterglow observations and it is now possible to better analyse their properties. We first studied the intrinsic optical afterglows of a sample of long GRBs finding an unexpected clustering and an hint of bimodality of the optical luminosity distribution. Through a Montecarlo simulation we proved that both the observed clustering and bimodality are not simply due to selection effects but should hide important information in the understanding of the nature of the afterglow emission. To this aim we are comparing the intrinsic properties of the optical afterglows with the ones observed in the X-rays. The increased quality of multi bands afterglows follow up allows us to study the X-Rays to optical inconsistencies with the standard models that are appearing both in the temporal (lightcurves) and in the spectral (SEDs) analysis. The obtained results are not in a good agreement with the simplest standard models elaborated in the pre-Swift era and open the door to new alternative scenarios. |
| Tue, Jun 03 2008, 16:00 | SISSA, Room D | AC | Paul Hancock (University of Sidney, Australia) | High-Frequency GPS sources from the AT20G survey The Australia Telescope Compact Array 20GHz survey [AT20G] is the first sensitive high-frequency all sky survey. The AT20G covers the entire sky south of the equator to detection limit of ~40mJy. Most sources detected at 20GHz also have near-simultaneous observations at 4.8 GHz and 8.6 GHz, making this an ideal sample for the detection of GPS sources which peak above 5GHz. Of the ~4000 sources in the AT20G catalogue approximately 20% are candidate high-frequency GPS sources. In this presentation I will outline the technology, methodology, aims, and uses of the AT20G, with particular focus on candidate GPS sources. |
| Thu, May 29 2008, 16:00 | SISSA, Room E | JC | Benoit Famaey (Brussels University) | Modified Newtonian dynamics and galaxy clusters: is the reconciliation possible? We summarize the status of Modified Newtonian Dynamics (MOND) in galaxy clusters. The observed acceleration is typically larger than the acceleration threshold of MOND in the central regions, implying that some dark matter is necessary to explain the mass discrepancy there. A plausible resolution of this issue is that the unseen mass in MOND is in the form of ordinary neutrinos with masses just below the experimentally detectable limit. In particular, we show that the lensing mass reconstructions of the clusters 1E0657-56 (the bullet cluster) and Cl0024+17 (the ring) do not pose a new challenge to this scenario. However, the mass discrepancy for cool X-ray emitting groups, in which neutrinos cannot cluster, pose a more serious problem, meaning that dark baryons could present a more satisfactory solution to the problem of unseen mass in MOND clusters. |
| Thu, May 22 2008, 16:00 | SISSA, Room E | SS | Giulia Migliori (SISSA) | The broadband Spectral Energy Distribution of the CSS quasar 3C 186 The importance of Compact Steep Spectrum (CSS) and Ghigahertz Peaked Spectrum (GPS) radio sources is double. They represent a possibility to investigate the interactions between the radio sources and the surrounding medium as well as an opportunity to shed a light on the evolution of the radio sources themselves. In my talk I will first summarize the main properties and results on CSS/GPS sources. Then, I will focus on the case of the CSS quasar 3C186. The spectral analysis based on a new Chandra observation is shown and the preliminary results of the study on the broadband (from radio to X-ray) spectrum are presented. We analyze the peculiarly high radio loudness and disentangle the contributions in the radio band from the nuclear and extended (i.e. jet, hot spots, lobes) components. Then we discuss the emission processes which could explain the spatially unresolved X-ray luminosity going over the components of the quasar. |
| Tue, May 20 2008, 16:00 | SISSA, Room D | HC | Steen Hansen (Dark Cosmology Center, Copenhagen) | How well do we understand cosmological dark matter structures? |
| Fri, May 16 2008, 12:00 | SISSA, Room E | IAS | Ajit Kembhavi (IUCAA, Pune) | Galaxy morphology and supermassive black holes |
| Thu, May 15 2008, 16:00 | SISSA, Seminar Room D | J | Sabino Matarrese (Physics Department and INFN, University of Padua) | Primordial non-Gaussianity and CMB: present constraints and future expectations |
| Thu, May 15 2008, 15:00 | SISSA, Room E | SS | Ernazar Abdikamalov (SISSA) | Relativistic Simulations of Gravitational Collapse of Compact Stars In the first part of my talk i will discuss our study of the gravitational collapse of neutron stars into quark hybrid stars induced by a phase transition from hadronic nuclear matter to deconfined quark matter in the neutron star core. We find that the spectrum of the gravitational waves produced by the collapse and bounce is dominated by the fundamental quasi-radial and quadrupolar pulsations modes of the star. In some cases the emission of gravitational radiation is considerably enhanced by a nonlinear resonance, which transfers energy from a strongly excited but weakly radiating mode into an originally less excited but efficiently radiating mode. Finally, we discuss the detectability of the gravitational-wave signals, showing that the signal-to-noise ratio for currently operating interferometers is sufficiently high for events in our Galaxy, while third-generation detectors could observe those occurring in the Virgo cluster. Theoretically, massive white dwarfs with O/Ne/Mg cores with high central densities experience rapid electron capture that leads to the collapse of the core. This is accretion-induced collapse (AIC), a path alternative to the stellar explosion associated with Type Ia supernova. In the second part, I will discuss our work in progress towards multi-dimensional simulations of AIC in general relativity. |
| Thu, May 08 2008, 16:00 | SISSA, Room E | SS | Barbara De Marco (SISSA) | Probing variability patterns of the Fe K line complex in bright nearby AGNs The unprecedented sensitivity of current X-ray telescopes allows for the first time to address the issue of the Fe K line complex variability patterns in bright, nearby AGNs. These kind of studies have the potential to map the accretion flow in the strong gravity regime of supermassive black holes. We examined XMM-Newton observations of a sample of 11 bright radio-quiet AGNs (for a total of 14 observations) with the aim of looking for relativistic iron emission lines, and characterizing their temporal behaviour. A systematic mapping of the emission exceeding the continuum in the 4-9 keV range is performed in the time vs energy domain, in order to identify interesting spectral features. The variability significance is assessed by extracting light curves and comparing them with Monte Carlo simulations. We detected significant line variability in the 5.4-7.2 keV band in 5 out of 14 observations. In the brightest source of the sample, IC 4329a, the detected line variations are characterized by intensity modulations on a time scale of 32.5 ks (at ~96% confidence level against random fluctuations) and apparently lagging, by 15 ks, behind the short-time scale ~0.3-10 keV continuum variability. This work increases the currently scanty number of detections of variable Fe emission lines. IC 4329a reveals a complex variability pattern, not immediately consistent with ``standard'' interpretations. |
| Wed, Apr 23 2008, 16:00 | SISSA, Room E | SS | Andrew Schurer (SISSA) | Modelling the effects of dust evolution on the SEDs of galaxies of different morphological type I will present photometric evolution of galaxies in which in addition to the stellar component the effects of an evolving dusty interstellar medium have been included with particular care. Starting from the work of Calura, Pipino \& Matteucci (07) in which chemical evolution models have been used to study the evolution of both the gas and dust components of the interstellar medium in spiral, elliptical and irregular galaxies, it has been possible to combine these models with a spectrophotometric stellar synthesis code that includes dust reprocessing (GRASIL) (Silva 1998) to analyse the evolution of the Spectral Energy Distributions (SED) of these galaxies. We test our models against observed SEDs both in the local universe and at high redshift and use them to predict how the attenuation curves and the percentage of starlight reprocessed evolves for each galaxy type. The importance of following the dust evolution is investigated by comparing our results with those obtained by adopting popular simplifications to treat this component. Possible errors from assuming a Milky Way dust composition and a dust to gas ratio scaling with the metallicity particularly in young galaxies, ellipticals and low metallicity galaxies are highlighted. |
| Tue, Apr 22 2008, 16:00 | SISSA, Room D | AC | Christopher Gordon (Oxford University, UK) | The Primordial Dipole Perturbation The dipole anisotropy in the cosmic microwave background is thought to be mainly due to our peculiar motion of about 369 km/s. For an almost scale invariant primordial power spectrum about 3% of the observed dipole comes from the intrinsic dipole on the surface of last scattering. However, if there is a bump in the primordial power spectrum at very large scales, then the contribution of the intrinsic dipole could be much higher. One potential method of measuring the primordial dipole is to compare the dipole seen in the CMB with that seen in a peculiar velocity survey. We show that current type Ia supernovae data is barely sufficient to detect the total dipole. Future data from the LSST may have the potential to detect the intrinsic dipole if it is about 5 sigma larger than the expected value from an almost scale invariant spectrum. |
| Thu, Apr 17 2008, 16:00 | SISSA, Room D | J | Francesco Ferraro (Department of Astronomy, University of Bologna) | Globular Clusters |
| Thu, Apr 17 2008, 11:00 | SISSA, Aula Magna | AC | George Smoot (Lawrence Berkeley National Laboratories and University of California Berkeley) | The Cosmic Microwave Background |
| Thu, Apr 10 2008, 16:00 | SISSA, Room E | SS | Sara Buttiglione (SISSA) | Radio Loud AGNs Optical Spectroscopy: Disk - Jet Relation We are analysing the optical data of a complete subsample of 114 Radio Loud Active Galactic Nuclei (RL AGNs) with redshift < 0.3 from the Third Cambridge Revised Catalogue (3CR) in order to study the accretion properties of different kinds of RL AGNs and to try to connect the properties of the accretion disk to the jets formation. We aim to determine if a particular accretion condition is necessary to prime the jets. We are investigating the radiation emitted by the accretion disk by studying the optical spectra of the sources in our sample. Our main results, so far, are collected in a set of diagnostic diagrams: through the comparison of emission line ratios we can obtain information about the main component of the ionising radiation (star formation, High Excitation Galaxies - HEG, Low Excitation Galaxies - LEG). We have also considered the importance of the AGN total luminosity to complete the characterisation of the source properties. We are still exploring the optical - radio connection: preliminary results show a mild correlation with the extended componet radio emission while the optical - radio correlation for the core component seems to show thighter correlations, both for HEG and for LEG. All these results are to be better investigated once the sample will be completed. |
| Tue, Apr 08 2008, 16:00 | SISSA, Room D | HC | Avery Meiksin (Edinburgh University, UK) | The Structure of the Intergalactic Medium |
| Tue, Apr 01 2008, 16:00 | SISSA, Room D | AC | Andrew Taylor (Max Planck Institute, Heidelberg, Germany) | The Propagation of Cosmic Ray Nuclei and What Can Be Acheived with Just a Pen In this talk I'll explain why cosmic ray nuclei should not be forgotten, particularly with regards to high energy neutrino flux calculations. I'll present my analytic results, and compare them to the Monte Carlo method. |
| Thu, Mar 27 2008, 16:00 | SISSA, Room E | SS | Pratika Dayal (SISSA) | Proving reionization using Lyman Alpha emitters We use a semi-analytic model of Lyman Alpha Emitters (LAE) to constrain the reionization history. By considering two physically motivated scenarios in which reionization occurs either early (ERM) (z_reionization = 7) or late (LRM)(z _reionization =6), we fix the global value of the IGM neutral fraction, leaving only the star formation efficiency and the effective escape fraction of Lyman alpha photons as free parameters. We show that the ERM fits the observed LAE luminosity function (LF) at z=5.7 and 6.5 requiring no redshift evolution or mass dependence of the star formation efficiency while the LRM requires a large drop in SFR efficiency from 6.5 to 5.7. Thus, the data seem to imply that the Universe was already highly ionized at z=6.5. We also show how the model compares to different observations, these being Equivalent width measurements, Weighted skewness and the global SFR density. |
| Thu, Mar 20 2008, 16:00 | ICTP, Seminar Room | J | Neil Turok (Centre for Mathematical Sciences, Cambridge, UK) | What banged? |
| Thu, Mar 13 2008, 16:00 | SISSA, Room E | SS | Stefania Salvadori (SISSA) | Life and times of Dwarf Spheroidal Galaxies The lack of a comprehensive scenario for the formation and evolution of dwarf spheroidal galaxies (dSphs) contrast with the large amount of available data for these nearby Local Group satellites. Recent observations of the stellar Metallicity Distribution Function (MDF) in four nearby dSphs, opened new questions pertaining to their origin: a significant lack of stars with [Fe/H] < -3 is observed in these galaxies, in contrast with the Galactic halo MDF in which the low [Fe/H]-tail extends down to [Fe/H] ~ -4 and even below. We investigate the formation and evolution of dSph galaxies, satellites of the MW, in their cosmological context by using a Monte Carlo method based on the semi-analytical EPS formalism. In our model dSphs form out of the MW environment, whose metallicity evolution depends on the efficiencies of star formation and mechanical feedback along the build-up of the Galaxy, fixed in order to match the general MW properties and the Galactic halo MDF. A global scenario for the formation and evolution of dSphs is proposed which accounts simultaneously for several observed properties of Sculptor, used as a dSphs template. |
| Tue, Mar 11 2008, 16:00 | SISSA, Room D | HC | Jordi Miralda-Escude (Barcelona University, Spain) | Methods to Probe Reionization and the First Objects |
| Thu, Mar 06 2008, 16:00 | SISSA, Room E | SS | Michael Cook (SISSA) | Two-Phase Galaxy Formation I will initially outline a two-phase evolutionary scenario for dark matter halos corresponding typically to a high-redshift merger driven evolution, followed by a quiescent increase in matter at lower redshifts, detailing the main theoretical and observational motivations supporting this approach. Secondly I will describe briefly our model governing the baryonic matter evolution within the evolving dark halos and highlight several key features. Finally I compare the model outputs to the z=0 galaxy population by matching to morphologies, gas fractions, stellar fractions, mass-light ratios, colour magnitudes, Tully fisher relations and Luminosity functions. I will conclude by addressing some of the limitations of this model and discussing directions currently underway for future development. |
| Thu, Feb 28 2008, 16:00 | SISSA, Room E | B | Annalisa Celotti and John Miller (SISSA) | Astrophysical Jets We will first introduce the different contexts in which astrophysical jets arise and summarise the conditions necessary for producing them. We will then talk about energetics for the outflows and give a brief overview of the Blandford/Znajek mechanism. Then we will hope to stimulate a discussion among the audience concerning emission mechanisms from jets, feedback and backgrounds. |
| Thu, Feb 21 2008, 16:00 | SISSA, Room E | JC | Illarionov Alexei (SISSA) | Tkachenko waves as sources of precession of the neutron stars I would like to discuss a simple model, in which long period precession of the isolated neutron star is powered by Tkachenko waves generated by a glitch. Based on a possible observation of a glitch in RXJ0720.4-3125. The period of precession, determined by a NS oblateness, should be equal to the standing Tkachenko wave period for the effective energy transfer from the standing wave to the precession motion. |
| Tue, Feb 19 2008, 16:00 | SISSA, Room D | AC | Ralf Lehnert (Center for Theoretical Physics, MIT ) | Theoretical topics in Relativity violations The breakdown of spacetime symmetries has recently been identified as a promising tool in the search for underlying physics possibly arising at the Planck scale. This talk will give a brief review of the motivations behind the idea and discuss various theoretical and phenomenological aspects in the subject. Particular emphasis will be given on topics with astrophysical or cosmological implications. |
| Thu, Feb 07 2008, 16:00 | SISSA, Room E | JC | Ana Babic (SISSA) | Cosmological evolution of supermassive black holes A model relating the history of supermassive black hole growth and the history of dark matter halo assembly is presented, and the model's observational consequences are discussed. Motivated by the model's prediction that the Eddington ratio averaged over the population of halos evolves strongly with epoch, the results of an investigation of Eddington ratios of AGN in the Chandra Deep Field South are discussed. |
| Thu, Jan 31 2008, 16:00 | SISSA, Room E | JC | Cristiano Germani (SISSA) | An Alternative to Inflation: the cosmological slingshot scenario In this talk I will introduce a non-inflationary way to solve the standard cosmological problems and predict the spectrum of primordial perturbation measured on the CMB by WMAP |
| Tue, Jan 29 2008, 16:00 | SISSA, Room E | AC | Serguei Vorobiov (University of Nova Gorica, Slovenia) | The Pierre Auger Observatory a new stage in the study of the ultra-high energy cosmic rays Since the first detection of a cosmic ray event with energy above 1020 eV in 1962, the nature and origin of these ultra-high energy cosmic rays (UHECR) remain unknown. The standard cosmic ray scenarios of the UHECR production invoke the acceleration of protons and heavier nuclei at the astrophysical objects such as active galactic nuclei, gamma-ray bursts or galaxy clusters. In these scenarios, it is expected that the cosmic ray flux should undergo a strong suppression (so-called GZK cut-off) at energies above approximately 1019.7 eV. The cosmic ray flux observed at the ultra-high energies is very small (about 1 cosmic ray per km2, per steradian and per year at 1018 eV). The experimental challenges necessary to constrain the essential parameters of the UHECR (energy, arrival direction, nature) are considerable, as these cosmic rays are observed indirectly, via secondary particle cascades (extensive air showers, EAS) induced by a primary particle in the atmosphere. This explains the noticeable differences between the results of the past generation cosmic ray experiments (AGASA, HiRes), in particular on the presence of the GZK cut-off in the UHECR energy spectrum. The new generation cosmic ray detector, the Pierre Auger Observatory (PAO) in Argentina, has been designed to answer the crucial questions of the UHECR physics. The experiment consists in large aperture (aiming at 7000 km2 sr above 1019 eV) hybrid detection (combining air fluorescence and ground particle techniques) of the same EAS. The hybrid measurements allow to improve significantly the precision on reconstructed primary cosmic ray parameters, and to perform cross-calibrations between the two techniques at the energies, unreachable with accelerator experiments. The project aims at covering the UHECR sky completely with two observation sites, one in the Southern and the other in the Northern hemisphere. The Southern Observatory is nearing its completion, and the amount of the data collected since the beginning of 2004 is now largely superior to that of the previous experiments. The Auger measurements of the UHECR energy spectrum, the results of the anisotropy search and the studies of the cosmic ray composition will be presented and discussed. |
| Thu, Jan 24 2008, 16:00 | SISSA, Room E | B | Luigi Danese (SISSA) | GRB and their host galaxies at high z |
| Tue, Jan 22 2008, 16:00 | SISSA, Room D, | AC | Emanuele Ripamonti (University of Insubria, Varese) | Feedback effects of black holes during reionization The observation of bright quasars at z~6 suggests that massive and luminous BHs were present at even earlier epochs. Starting from semi-analytical models of the evolution of the cosmological density of BHs, I look at the feedback effects of their emission during the reionization epoch (30>~ z >~ 5). I find that the "neutral" IGM (i.e. the regions which are reionized late, as they are removed from luminous sources) is easily heated to ~ 1000-10000 K by the soft X-rays produced by BHs; this should leave an observable signature upon the 21 cm emission. Furthermore, the heating of the IGM increases the "critical mass" an halo needs in order for its gas to be able to cool, collapse and form stars: at z<~10 such mass goes from 105-106 Msun to 107-108 Msun, and the formation of low mass halos is largely suppressed. This last effect is even stronger when the surroundings of a BH are considered, both because the critical mass is raised to higher levels, and because even halos above the critical mass can lose a large fraction of their gas. |
| Tue, Jan 15 2008, 16:00 | SISSA, Room D | J | Richard Bond (Canadian Institute for Theoretical Astrophysics, Toronto, Canada) | Cosmic Microwave Background and Cosmological Concordance Model |
| Thu, Jan 10 2008, 16:00 | SISSA, Room E | JC | Bruneton J.-P. (SISSA) | MOND-selected topics |
| Tue, Jan 08 2008, 16:00 | SISSA, Room D | HC | Sabine Schindler (Innsbruck University, Austria) | Metal Enrichment of the Intra-Cluster Medium |
| Thu, Dec 13 2007, 16:00 | SISSA, Room D | AC | Aurelio Grillo (Gran Sasso National Laboratories, l'Aquila) | Latest results from the Auger experiment |
| Wed, Dec 12 2007, 16:00 | SISSA, Room E | IAS | Ilia Musco (Queen Mary University of London, UK) | Primordial Black Hole formation with cosmological curvature perturbations. We study Primordial Black Hole (PBH) formation in the early universe. Working within spherical symmetry, we specify an initial configuration in terms of a curvature perturbaion, specifing a curvature profile. In general this represents initial conditions for general metric perturbations away from the homogeneous Friedmann Robertson Walker model that can lead to PBH formation for large amplitude perturbations of the metric. Using an asymptotic quasi-homogeneous solution, we relate a generic curvature perturbation with the hydrodynamical perturbations of the cosmological fluid, which at an early enough time, when the length scale of the configuration is much larger than the cosmological horizon, can be treated as small perturbations of the background values. This solution enable us to consider in a self-consistent way the formation of PBHs in a wide variety of cosmological situations. We show also the possibility to link in a self consistent way the numerical results describing the relaivistic collapse of a single non linear perturbation, with the initial spectrum of cosmological perturbation obtained from inflation. |
| Tue, Dec 11 2007, 16:30 | SISSA, Room D | HC | Abhay Ashtekar (Penn State, USA) | Quantum Nature of the Big Bang in Simple Models According to general relativity, space-time ends at singularities and classical physics just stops. In particular, the big bang is regarded as The Beginning. However, general relativity is incomplete because it ignores quantum effects. Through simple models, I will illustrate how the quantum nature of space-time geometry resolves the big bang singularity. Quantum physics does not stop there. Indeed, quantum space-times can be vastly larger than what general relativity had us believe, with unforeseen physical effects in the deep Planck regime. |
| Thu, Dec 06 2007, 16:00 | SISSA, Room E | JC | Kristopher Gutierrez (SISSA) | High Energy Observations: Cosmic Rays and Black Holes |
| Tue, Dec 04 2007, 16:00 | SISSA, Room D | AC | Ignacio Ferreras (Mullard Space Science Laboratory University College London) | Exploring the formation of massive early-type galaxies Extracting the formation history of galaxies from the properties of their (unresolved) stellar populations poses a major challenge. This problem is even harder in early-type galaxies, whose light is dominated by old, passively evolving stars. I will give a general overview of the field and present a novel approach to the extraction of star formation histories by the use of multivariate techniques such as Principal Component Analysis. |
| Tue, Nov 27 2007, 16:00 | SISSA, Room E | IAS | Michele Liguori (DAMTP, University of Cambridge, UK) | Looking for primordial non-Gaussianity with Planck |
| Tue, Nov 20 2007, 16:00 | SISSA, Room D | AC | Bruno Giacomazzo (Albert Einstein Institute, Potsdam, Germany) | General relativistic magnetohydrodynamics Binary Neutron Stars mergers are not only important sources of gravitational waves, but they are also thought to be at the origin of very important astrophysical phenomena, such as short gamma-ray bursts. In order to describe the dynamics of these events one needs to solve the full set of general relativistic hydrodynamics and magnetohydrodynamics (GRMHD) equations through the use of parallel numerical codes. After an overview on the status of numerical relativity at AEI, I will present the new Whisky(MHD) code developed to solve the equations of GRMHD on dynamical spacetimes in three spatial dimensions and with adaptive mesh refinement techniques. I will then report on some recent achievements obtained using this code in simulating binary neutron stars mergers with and without magnetic fields. |
| Tue, Nov 13 2007, 16:00 | SISSA, Room D | HC | Cristiano Cosmovici (IFSI / INAF, Italy) | Highlights in Bioastronomy (The Search for Primordial Life in the Galaxy) |
| Wed, Oct 31 2007, 16:00 | SISSA, Room E | IAS | Saumyadip Samui (IUCAA, Pune, India) | Probing the star formation history using the redshift evolution of luminosity functions |
| Mon, Oct 29 2007, 14:00 | SISSA, Room E | IAS | Massimo Merengo (CfA, Cambridge, MA, USA) | A Spitzer View of the epsilon Eridani Planetary System When a "radial velocity" planet was discovered orbiting our neighbour star epsilon Eridani, it was thought that the home of the Star Trek "Vulcans" was finally found. Even though it was later determined that Dr. Spock was originally from a different stellar system, epsilon Eridani remains the best available example to study a younger, dustier solar system analog. With an age of 850 Myr and a spectral type of K2V, it is a young main sequence star with a mass just below that of the Sun. Apart for the Jupiter-size planet detected with radial velocity techniques, it also harbors a dusty "debris disk" found by IRAS and first imaged at sub-mm wavelengths, roughly the size of our own Kuiper belt. These characteristics, and the proximity of epsilon Eridani to the Sun (just 3.2 pc), make it the ideal subject to study what could have been the early history of our own solar system. The Spitzer Space Telescope, with its high sensitivity and stability, offers a unique perspective to complete this picture, at wavelengths where the dust emission from the disk are stronger, and it is easier to search for direct emission from sub-stellar companions. |
| Fri, Oct 26 2007, 12:00 | SISSA, Room E | IAPS | Marina Cortes (University of Sussex, Brighton, UK) | On what scale should inflationary observables be constrained? We examine the choice of scale at which constraints on inflationary observables are presented. We describe an implementation of the hierarchy of inflationary consistency equations which ensures that they remain enforced on different scales, and then seek to optimize the scale for presentation of constraints on marginalized inflationary parameters from WMAP3 data. For models with spectral index running, we find a strong variation of the constraints through the range of observational scales available, and optimize by finding the scale which decorrelates constraints on the spectral index nS and the running. This scale is k = 0.017Mpc^-1, and gives a reduction by a factor of more than four in the allowed parameter area in the nSr plane (r being the tensor-to-scalar ratio) relative to k = 0.002Mpc^-1. These optimized constraints are similar to those obtained in the no-running case. We also extend the analysis to a larger compilation of data, finding essentially the same conclusions. |
| Thu, Oct 18 2007, 16:00 | Villa Bazzoni, Conference Room | J | Rachel Somerville (Max Planck Institute for Astronomy, Heidelberg, Germany) | AGN feedback: Where, When, and How? It has become increasingly clear that 'standard' models of galaxy formation set within the hierarchical Cold Dark Matter paradigm fail to reproduce observed galaxy properties in several important ways. The energy released by accretion onto supermassive black holes in galaxies is a promising new ingredient that could solve many of these problems. I will discuss the physical mechanisms whereby AGN are thought to be able to couple with their surroundings, and assess the feasibility of this proposal from the standpoint of empirical energy constraints from observations. Then, I will present new observational results on the environment and redshift dependence of quenched galaxies (the "victims") -- as well as of the smoking guns (the AGN themselves), and compare these with predictions from semi-analytic models from several different groups. |
| Tue, Sep 25 2007, 16:00 | SISSA, Room D | AC | Jason Dick (University of Calivornia Davis, USA) | Constraining inflation with the South Pole Telescope |
| Thu, Sep 20 2007, 16:00 | Villa Bazzoni, Conference Room | J | Bruce Elmegreen (IBM Watson Research Center, USA) | Star formation in High Redshift Galaxies The Hubble Space Telescope for optical and near-infrared light and the Spitzer Space Telescope for the infrared have opened up a view of star formation in young galaxies that has never been possible before. Because the most distant galaxies are viewed as they were when light left them long ago, we can see the various steps of galaxy formation throughout time. Our work in the last three years has concentrated on the nature of star formation in these galaxies, many of which are quite peculiar by the standards of our own neighborhood. The dominant peculiarity is the presence of enormous young clusters and star complexes in the disk systems. These complexes are 1000 times more massive than any star forming regions in galaxies today, and yet they appear to form by standard processes, which begin with a localized collapse of disk gas. The galaxy disks are also smaller and thicker than today's spiral galaxies, and many have less than 1/10 the mass of the Milky Way. This combination of small galaxies and big star complexes makes the youngest disks look very patchy, yet, remarkably, the average positions of these patches, if they were to be smoothed out in each disk, has the same radial density profile as that observed in the more normal spiral galaxies that are also in deep fields. The thicknesses of the star complexes are also about equal to the galaxy thicknesses. Thus it appears that spiral galaxy disks form by the dispersal and dissolution of giant star complexes, which form by gravitational instabilities in thick and turbulent gas layers. This process seems to accompany the growth of galaxy disks over cosmic time, indicating that the growth occurs primarily by the accretion of gas for systems that end up as spirals. Clumpy disk star formation also precedes the formation of spirals and ellipticals, going back to the bandshifting limit of the ACS camera on HST, which is z~5. Thus most star formation in the Universe begins in disk systems, and from these, all of today's Hubble types eventually form. |
| Thu, Jul 05 2007, 6:00 | SISSA, Room D | IAS | Bruce Basset (Portsmouth University, UK) | Chasing dark energy with large scale surveys |
| Thu, Jun 28 2007, 14:00 | SISSA, Room E | IAS | Tina Kahniashvili (New York University, USA) | Gravitational radiation from primordial turbolence |
| Tue, Jun 26 2007, 16:00 | SISSA, Room D | AC | Ettore Carretti (INAF-IRA, Institute for Radioastronomy, Bologna) | CMBP B-Mode and Galactic synchrotron emission The B-mode of the CMB polarization is one of the most powerful tools to attempt the detection of the GW background left by the Inflation. Main CMBP issue, however, is its faint signal, so that Galactic foreground emissions can limit the minimum detectable radiation. In this presentation I will discuss about one of the most important contaminant, the Galactic synchrotron background: what is known so far (few), and the limits of the CMBP detection we can estimate with the available data. I will also present the ongoing surveys we are conducting at 2.3 GHz (PGMS and S-PASS) to improve our knowledge of this not yet sufficiently studied emission. |
| Thu, Jun 21 2007, 16:00 | SISSA, Room D | J | Albert Stebbins (Fermilab, Chicago, Illinois, USA) | Cosmological Large Scale Structure |
| Tue, Jun 19 2007, 16:00 | SISSA, Room D | IAS | Tirth Choudhury (Institute of Astronomy, Cambridge, UK) | Observational constraints on dark ages and cosmic reionization The study of dark ages and reionization is of immense importance in cosmology since they are directly related to the formation of first large scale structures. Research in this area received a big boost due to availability of a variety of observational data accumulated over the past few years with additional progresses expected soon from a number of different ground-based and space-born experiments. In this talk, I will review our understanding of the physical processes related to cosmic reionization based on available data and also discuss future prospects. |
| Tue, Jun 12 2007, 16:00 | SISSA, Room D | HC | Gabriele Ghisellini (INAF, Astronomical Observatory of Brera-Merate) | Gamma Ray Bursts |
| Thu, Jun 07 2007, 6:00 | SISSA, Room E | B | Andrea Ferrara | The first game In order to ensure a lively flow of opinions and stimulate the emergence of innovative views, I will drive the audience through a scientific game involving our picture of the most ancient epochs of the cosmos. |
| Thu, Jun 07 2007, 2:00 | SISSA, Room E | IAS | Mercedes Molla (University of Madrid, Spain) | Chemical and spectrophotometrical evolution of spiral galaxies We will show the predicted results computed for a wide grid of spectro-photometrical models applied to spiral and irregular galaxies. They have been calculated consistently with evolutionary synthesis models which uses as input the information proceeding from chemical evolution models from Molla & Diaz (2005). The comparison of the available spectro-photometrical data, such as spectral energy distribution, colors or spectral indices , with the predictions of single stellar population (SSP) model only to allow to us to determine the averaged stellar age and metallicity for the mix of stellar populations. This is a lost of information, since single averaged values are not sufficient to determine the complex star formation and enrichment history. On the other hand, the chemical abundances and other present time data constraint the possible evolutionary histories in those galaxies. Thus, by using both kind of methods, synthesis and chemical codes, we may determine these histories in spirals with high precision. |
| Thu, May 31 2007, 13:30 | SISSA, Room E | SS | Andrew Schurer | Dust Reprocessing in Galaxies Interstellar dust is a very important component of galaxies and a rigorous treatment must be adopted for a wide range of studies including the modeling of SEDs and the determination of the star formation rate. This galactic component has been treated in several different ways of varying complexity. I will discussone of these models GRASIL (Silva 1998), which computes the spectral evolution of stellar systems taking into account the effects of dust which is distributed within the model galaxy with a realistic geometry. I have used the GRASIL code to reproduce observations of a wide range of galaxies of different morphology within the local universe. I will present some of my results and discuss their implications and limitations and show what problems with the model they highlight. I will conclude by discussing my planned future work which will involve studying the evolution of the interstellar dust component and potentially creating and coupling a dust evolution model with the GRASIL code. |
| Tue, May 29 2007, 16:00 | SISSA, Room D | AC | Crescenzo Tortora (Federico II University, Naples) | Gravitational lensing versus dark matter and cosmology Gravitational lensing in the strong and weak regimes gives rise to spectacular events such as multiple and magnified images of the same source, Einstein rings, giant arcs and arclets in galaxy clusters. Both the distance scale (through the Hubble constant) and the energy content of the universe may be investigated through lensing. Indeed, while the time delays in multiply imaged systems may be used to infer the Hubble constant, it is possible to recover information on the dark energy nature both using strong lensing events and weak lensing by the large scale structure. In addition, the distribution of dark matter can be tested in galaxy and clusters of galaxies. A key role in the strong lensing regime is played by the modeling of the lens. I will show in detail how this can affect the estimate of the Hubble constant, thus arguing for the need of general classes of parametric models for galaxies and clusters, in order to achieve the maximum quantity of information with a little number of initial hypothesis on the form of gravitational potential. Then, one has to compare the results from lensing with those from dynamical analysis or numerical simulations, in order to understand why galaxies are like we observe them and study their evolutive paths. |
| Thu, May 24 2007, 13:30 | SISSA, Room E | SS | Michael Cook | Formation of galaxy disks and the origins of the disk-spheroid dichotomy We are developing a semi-analytical description for the formation and evolution of galaxy disks within a hierarchical cosmology. Tracking the dissipationless collapse of gas within a dark matter halo, we are able to follow the growth of a galaxy disk annuli-by-annuli. This has enabled us to begin the evaluation of some of the evolutionary properties of galaxy disks (dynamics, structure, star formation rates, gas fraction evolution etc). In order to make comparisons with galaxy populations we have coupled the outputs of the disk model to the spectrophotometric code GRASIL in order to provide the broad-band magnitudes for a generated population of galaxy disks. This is now enabling us to analyse several observed galaxy disk relations; such as the Tully-Fisher relation and luminosity functions. In the last few years 'standard' semi-analytical galaxy formation models have found several observations troublesome to reproduce, therefore some authors have begun looking at alternative scenarios. We have begun the investigation of a scenario for galaxy formation which comprises of two phases: A high redshift phase where the formation of spheroids (ellipticals and galaxy bulges) dominated, as envisaged by Granato et al. 2004, and the lower redshift phase dominated by the quiescent formation and growth of disks. In this way we plan to model the formation of galaxy disks along with the anti-hierarchical baryon (ABC) scenario of galaxy formation in a consistent way, with the aim of analysing the origins of the observed disk-spheroid dichotomy in the Universe. |
| Tue, May 22 2007, 16:00 | SISSA, Room D | AC | Paolo Padoan (University of California San Diego, USA) | The Stellar IMF Now and Then The observed mass distribution of stars can be understood as the effect of supersonic turbulence in present-day star forming environments. I will present results of numerical simulations of supersonic turbulence that have allowed us to quantify universal statistical properties of supersonic turbulence. These properties can then be used to derive a statistical model for the origin of stellar mass distribution as a function of turbulent rms velocity, mean gas density, temperature and magnetic field strength. The model predicts the existence of a critical magnetic field strength below which the slope of the power law range of the stellar IMF becomes very steep. This suggests that the IMF of population III or early population II stars may be much steeper than a Salpeter IMF, though probably shifted to a larger mean mass, of order 10 solar masses. I will then present results from the largest simulations of supersonic turbulence to date, confirming the validity of the predictions of the simple statistical model for the origin of the IMF. |
| Thu, May 17 2007, 16:00 | Villa Bazzoni, Conference Room | J | Max Pettini (Institute of Astronomy, Cambridge, UK) | Lyman-break galaxies and their interaction with the IGM |
| Thu, May 17 2007, 13:30 | SISSA, Room E | SS | Marcos Valdes | Constraining dark matter through 21 cm observations Beyond reionization epoch cosmic hydrogen is neutral and can be directly observed through its 21 cm signal. If dark matter (DM) decays or annihilates the corresponding energy input affects the hydrogen kinetic temperature and ionized fraction, and contributes to the Lyman alpha background. The changes induced by these processes on the 21 cm signal can then be used to constrain the proposed DM candidates, among which we select the three most popular ones: 25 keV decaying sterile neutrinos, 10 MeV decaying cold DM and 10 MeV annihilating cold DM. Although we find that the DM effects are considerably smaller than found by previous studies (due to a more physical description of the energy transfer from DM to the gas), we conclude that combined observations of the 21 cm background and of its gradient should be able to put constrains at least on cold DM candidates. |
| Tue, May 15 2007, 16:00 | SISSA, Room D | IAS | Giampiero Mangano (INFN, University of Naples Federico II) | Present bounds on the relativistic energy density in the Universe from cosmological observables We discuss the present bounds on the relativistic energy density in the Universe parameterized in terms of the effective number of neutrinos N using the most recent cosmological data on Cosmic Microwave Background (CMB) temperature anisotropies and polarization, Large Scale galaxy clustering from the Sloan Digital Sky Survey (SDSS) and 2dF, luminosity distances of type Ia Supernovae, Lyman-alpha absorption clouds (Ly-alpha), the Baryonic Acoustic Oscillations (BAO) detected in the Luminous Red Galaxies of the SDSS and finally, Big Bang Nucleosynthesis (BBN) predictions for 4He and Deuterium abundances. We find N= 5.2+2.7-2.2 from CMB and Large Scale Structure data, while adding Ly-alpha and BAO we obtain N= 4.6+1.6-1.5 at 95 % c.l.. These results show some tension with the standard value N=3.046 as well as with the BBN range N= 3.1+1.4-1.2 at 95 % c.l., though the discrepancy is slightly below the 2-sigma level. In general, considering a smaller set of data weakens the constraints on N. We emphasize the impact of an improved upper limit (or measurement) of the primordial value of 3He abundance in clarifying the issue of whether the value of N at early (BBN) and more recent epochs coincide. |
| Thu, May 10 2007, 13:30 | SISSA, Room E | SS | Luca Naso | Magnetic field in proto-neutron stars and in accretion discs The present understanding of the processes which determine the magnetic field observed in neutron stars is still far from being complete. The existence of magnetic fields with different strengths and distributed on different lengthscales can be explained in terms of a dynamo mechanism driven by rotation and turbulent motions. Here we focus our attention on the turbulent mean-field dynamo action, which may be excited in the Neutron Finger Unstable zone. We report results of a 1D model, which includes the feedback processes which tend to saturate the growth of the magnetic field (i.e., \alpha-quenching) and suppress its turbulent diffusion (i.e., \eta-quenching). The set of equations describing the system is evolved numerically under a very large variety of initial conditions (spin period of the PNS, strength of the differential rotation, intensity of the seed magnetic field, and extension of the unstable zone). The second part ofthe seminar is about accretion discs onto magnetized neutron stars. According to the Magnetically Threaded Disc model, the interaction between the stellar magnetosphere and the disc should generate an azimuthal component for the magnetic field. Our first aim is to find an expression for this component by means of a semi-anlytic procedure. Interesting preliminary results are shown. |
| Tue, May 08 2007, 6:00 | SISSA, Room D | HC | Valeria Ferrari (University of Rome La Sapienza) | Studying gravitational wave sources in preparation for Gravitational Wave Astronomy |
| Thu, May 03 2007, 3:30 | SISSA, Room E | SS | Barbara de Marco | Transient Relativistically Shifted Emission Lines in Radio Quiet AGNs Recent XMM-Newton observations have revealed the presence of short-time scale variable narrow emission lines in the 5-6 keV energy range of several Seyfert 1 galaxies [e.g. Iwasawa, Miniutti & Fabian 2004; Turner et al. 2006; Tombesi et al. 2007]. The nature of these lines is not yet understood, but it seems they can be attributed to Fe K(alpha) emission from illuminated spots on the innermost regions of the accretion disc [Dovciak et al. 2004]. The lines appear redshifted because of relativistic effects due to the proximity of the central black hole. Their variability pattern represents a powerful tool for studying the dynamics of the innermost accretion flow and inferring physical parameters of the system, such as the accretion disc inclination and the black hole mass. In this talk I will present a systematic study of a sample of radio quiet AGN. The aim is to perform a detailed time-resolved analysis in the X-ray band in order to look for transient emission lines and to trace their variability pattern. |
| Tue, Apr 24 2007, 16:00 | SISSA, Room D | AC | Stefano Cristiani | The CODEX-ESPRESSO Experiment: Cosmic Dynamics, Fundamental Physics, Planets and much more... |
| Thu, Apr 19 2007, 16:00 | Villa Bazzoni, Conference Room | J | Piero Madau (University of California, Santa Cruz, USA) | Cold Dark Matter Substructure in Galaxy Halos |
| Tue, Apr 17 2007, 16:00 | SISSA, Room D | IAS | Kazushi Iwasawa (Max Planck Institute for extra-Terrestial Physics, Garching, Germany) | X-ray probing for AGN power in the most luminous infrared galaxies |
| Tue, Mar 20 2007, 16:00 | SISSA, Room D | AC | Bodo Ziegler (Institute for Astrophysics, Goettingen, Germany) | Evolution in structure and internal kinematics of spiral galaxies |
| Thu, Mar 15 2007, 16:00 | ICTP, Conference Room | J | Michele Maggiore (University of Geneva, Switzerland) | Gravitational Waves: Theory and Observations |
| Tue, Mar 13 2007, 16:00 | SISSA, Room D | HC | Eline Tolstoy (Kapteyn Observatory, Groningen, The Netherlands) | Galactic Archaeology |
| Mon, Mar 12 2007, 16:00 | SISSA, Room E | J | Yasunori Fujii (Advanced Research Institute for Science and Engineering, Waseda Univ., Japan) | Scalar-tensor theory, the accelerating universe and the time-dependent fine-structure constant, II |
| Tue, Mar 06 2007, 6:00 | SISSA, Room D | AC | Olindo Zanotti (University of Bologna, Italy) | Pulsar magnetospheres: theoretical models and numerical simulations |
| Mon, Mar 05 2007, 6:00 | Villa Bazzoni, Conference Room | J | Yasunori Fujii (Advanced Research Institute for Science and Engineering, Waseda Univ., Japan) | Scalar-tensor theory, the accelerating universe and the time-dependent fine-structure constant, I |
| Tue, Feb 27 2007, 16:00 | SISSA, Room D | AC | Ruben Salvaterra (Univ. Milano Bicocca, Italy) | The GRB Luminosity Function: Insights from Swift |
| Thu, Feb 15 2007, 16:00 | SISSA, Room D | J | Andy Fabian (Institute of Astronomy, Cambridge, UK) | Observations of AGNs |
| Wed, Feb 14 2007, 16:00 | SISSA, Room D | IAS | Jens Niemeyer (Institute for Theoretical Physics and Astrophysics, University of Wurzburg, Germany) | Theoretical Astrophysics and Particle Physics |
| Tue, Feb 13 2007, 16:00 | SISSA, Room D | HC | Julian Chela-Flores (ICTP) | Astrophysics and Astrobiology: A Common Search for Our Origins |
| Tue, Feb 06 2007, 6:00 | SISSA, Room D | AC | Massimo Meneghetti (INAF, Astronomy Institute of Bologna) | Unveiling the inner structure of galaxy clusters with strong lensing |
| Tue, Jan 30 2007, 16:00 | SISSA, Room D | APC | Julien Lesgourgues (LAPTH, Annecy, France) | Prospects of Measuring Neutrino Masses with Cosmological Observations |
| Wed, Jan 24 2007, 14:00 | SISSA, Room E | IAS | Eduardo Guendelman (Ben-Gurion University, Beer-Sheva, Israel) | Vacuum Energy and Child Universes |
| Tue, Jan 23 2007, 16:00 | SISSA, Room D | AC | Harald Dimmelmeier (Max Planck Institute for Astrophysics, Garching, Germany) | Encouraging results for the extragalactic search for gravitational waves from core collapse supernovae |
| Thu, Jan 18 2007, 16:00 | ICTP, Conference Room | J | Viatcheslav Mukhanov (ASC, Physics Department, Munich, Germany) | Inflation: Confronting Predictions with Observations |
| Wed, Jan 10 2007, 11:00 | SISSA, Room E | HC | Jean-Loup Puget (Institute for Space Astrophysics, Paris, France) | Cosmic Infrared Background: latest results from Spitzer |
| Mon, Jan 08 2007, 4:00 | SISSA, Room E | IAS | Alessandra Silvestri (Syracuse University, Syracuse, New York, USA) | Dynamics of Linear Perturbations in Modified Gravity |
Legend:
- HC: Highlight Colloquium
- AC: Astrophysics Colloquium
- IAS: Informal Astrophysics Seminar
- IAPS: Informal Astroparticle Seminar
- J: Joint DAUT-ICTP-INAFTS-SISSA Colloquium
- JC: Journal Club
- SS: Student Seminar
- B: Brainstorming
Nearby seminars:
High Energy SectorSISSA
DAUT/OAT seminars
ICTP High Energy Sector
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