SEMINAR ANNOUNCEMENT - OAT and DAUT SEMINAR-Wedn. October 25, at 11:00 a.m. (PLEASE NOTE TIME) at Villa Bazzoni

[Gabriella Schiulaz]

I announce you the next seminar at OAT
(Please note that time is 11:00 a.m.)

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                    OAT-DAUT SEMINAR 
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Speaker: Meg Urry (Yale University) 

Title: Supermassive Black Holes in Deep Surveys 

Date: Wednesday, October 25th, 2006 
Time: 11:00 a.m.
Venue: Villa Bazzoni 

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Abstract: 
In principle, counting Active Galactic Nuclei (AGN) reveals the demographics of supermassive black holes. Optical/UV surveys easily find AGN out to high redshift, and they are numerous in the early Universe (z~2-3); however, if obscuration is important, as suggested by local AGN unification and by the spectrum of the X-ray background, the true number could be much larger. Using the deepest data from the Spitzer, Hubble, and Chandra Observatories, the Great Observatories Origins Deep Survey (GOODS) project reveals evidence for a substantial population of obscured AGN, with which we can explain the integrated X-ray background, the redshift distributions in deep X-ray surveys, and the infrared number counts of AGN. We can also directly estimate the AGN contribution to the extragalactic infrared background. With the larger-area MUSYC survey, we extend this work to higher luminosity AGN, and we report the discovery of new EXOs (Extreme X-ray Objects). Finally, combining all the large, deep, multiwavelength surveys, we find that the fraction of obscured AGN increases with redshift.
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Future Seminars


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OAT-DAUT SEMINAR 
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Speaker: Massimo Capaccioli (VST Center and INAF-OACN, Napoli) 
Title: The VLT Survey Telescope 
Date: Monday, October 30th, 2006 (PLEASE NOTE DAY)
Time: 12:00 
Venue: Villa Bazzoni 



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OAT-DAUT SEMINAR 
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Speaker: Matteo Viel (INAF/Oss. Astron. di Trieste) 
Title: Strong MgII systems in quasar and gamma-ray burst spectra 
Date: Wednesday, November 8th, 2006 
Time: 12:00 noon 
Venue: Villa Bazzoni 

Abstract: 
Strong MgII absorption (with equivalent width W>0.3 Angstrom) is produced in patchy gaseous envelopes, up to impact parameters of 80 kpc/h, surrounding galaxies of different morphological types. The incidence of these systems in gamma-ray bursts (GRB) and BL Lac spectra is a few times higher than in quasar (QSO) spectra. I investigate several possible explanations for this effect including: dust obscuration bias, clustering of the absorbers, different beam sizes of the sources, magnification bias of GRBs (i.e. microlensing events), association of the absorbers with the GRB event or the circumburst environment. 


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OAT-DAUT SEMINAR 
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Speaker: Enrico Maria Corsini (Univ. di Padova) 
Title: Direct measurements of bar pattern speed: implications for dark matter distribution and gas fueling in the center of barred galaxies 

Date: Wednesday, November 15th, 2006 
Time: 12:00 noon 
Venue: Villa Bazzoni 

Abstract: 
The dynamics of a barred galaxy depends on the pattern speed of its bar. The only direct method for measuring the bar pattern speed is the Tremaine-Weinberg technique. This method is best suited to gas-poor galaxies and therefore it has been restricted to early-type barred galaxies. On the other hand, a variety of indirect methods, which are based on the analysis of the distribution and dynamics of the gaseous component, has been used to measure the bar pattern speed in late-type barred galaxies. Nearly all the measured bars are as rapidly rotating as they can be. By comparing these results with recent high-resolution N-body simulations of bars in cosmologically-motivated dark matter halos, it is possible to conclude that these bars are not located inside centrally-concentrated halos. The Tremaine-Weinberg technique also permitted us to establish directly that nested bars are rotating with different pattern speeds and, in particular, that the rotation frequency of the secondary bar is higher than that of the primary one. This makes double bars efficient agents in fueling the AGN activity. 



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OAT-DAUT SEMINAR 
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Speaker: Simone Recchi (INAF/Oss. Astr. Trieste) 
Title: Early evolution of Tidal Dwarf Galaxies 
Date: Wednesday, November 22nd, 2006 
Time: 12:00 noon 
Venue: Villa Bazzoni 

Abstract: 
I will present a progress report of a project concerning the dynamical and chemical evolution of Tidal Dwarf Galaxies. Tidal tails, resulting from the interactions of large galaxies, can create self-gravitating structures which are the seeds of dwarf galaxies. In these galaxies, commonly known as Tidal Dwarf Galaxies , the Dark Matter content is very small, which make them more vulnerable to stellar feedback. Our first step is therefore to understand whether a model galaxy without Dark Matter can sustain the feedback of the ongoing star formation. We present tests of the evolution of models in which star formation efficiency, temperature threshold, initial distribution of gas and infall are varied. We conclude that it is feasible to keep a fraction of gas bound for several hundreds of Myr and that the development of galactic winds does not necessarily stop continuous star formation. At the end of my presentation I will briefly introduce a project concerning the self-enrichment of Globular Clusters. I shall summarize the chemical properties of Globular Clusters, focusing on the hints that some of the stars of the Globular Clusters are polluted by the ejecta released by older stars, probably of intermediate-mass, demonstrating therefore that Globular Clusters are not coeval objects. I will show the strategies and the first results adopted to sharpen our understanding on these issues. 
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For additional information on scheduled OAT seminars see:
http://adlibitum.oats.inaf.it/seminari/

Gabriella Schiulaz
segreteria OAT
Phone: 040-3199241
schiulaz at oats.inaf.it
segreteria at oats.inaf.it