I.C.R.A. Network - Weekly Seminars for May 2013

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Weekly Seminars

Weekly Seminars for May 2013

Friday May 3, 2013 - 4,00 pm

Aula Rasetti (Physics Dept., Old Building - 2nd Floor)

ICRA Seminar

Speaker: Dr.ssa Orchidea Maria LECIAN

Institution: Sapienza Università di Roma & ICRA

Title: Statistical maps for cosmological billiards.

Abstract:

Cosmological billiards are a representation of the solution of the Einstein equations in the asymptotical limit close to the cosmological singularity, when the most general symmetry for the metric tensor is assumed, and under the BKL (Belinski-Khalatnikov-Lifshitz) paradigm, for which points are spatially decoupled. The features of these structures are examined in 4=3+1 spacetime dimensions, where two different kinds of billiards are obtained. The symmetries of these billiards allow for several symmetry-quotienting mechanisms, which can be implemented according to different geometrical features, and which result into different statistical maps. The quantum regime of the model contains the information encoded in the statistical maps.

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La Segreteria ICRA

c/o Dipartimento di Fisica

Sapienza Università di Roma
P.le A. Moro, 5
I - 00185 ROMA, Italy
tel.: +39 06 4991 4 254
fax: +39 06 4454992
email: segreteria@icra.it

Monday May 6, 2013 - 4,00 pm

Aula Conversi (Physics Dept., Old Building - 1st Floor)

Physics Dept./ICRA joint Seminar

Speaker: Dr.ssa Michela MAPELLI

Institution: INAF - Osservatorio Astronomico di Padova

Title: Simulating young star clusters with different metallicity: impact on structural evolution and stellar exotica.

Abstract:

In this talk, I present an upgraded version of the public code STARLAB, in which we implemented metal-dependent stellar evolution, stellar winds from Wolf-Rayet and luminous blue variable stars, and new recipes for the formation of stellar remnants. This code is suitable for simulating young dense star clusters (SCs) with different metallicity. I discuss the results of a set of simulations of young dense SCs, with metallicity ranging from 0.01 solar up to solar. The metallicity plays a crucial role for both the structural e! volution of the SC and the formation of stellar exotica. As for the structural evolution, I show that mass-loss by stellar winds influences the reversal of core collapse and the expansion of the half-mass radius. In particular, the post-collapse re-expansion of the core is weaker for metal-poor SCs than for metal-rich SCs, because the former lose less mass (through stellar winds) than the latter. As a consequence, the half-mass radius expands faster in metal-poor SCs. The difference in the half-light radius between metal-poor SCs and metal-rich SCs is larger than the difference in the half-mass radius. As for the stellar exotica, I discuss the formation and the dynamical evolution of massive (>25 Msun) stellar black holes (MSBHs) in metal-poor SCs. I show that they can contribute significantly to the population of X-ray binaries and of double-degenerate binaries.

**************************************************

La Segreteria ICRA

c/o Dipartimento di Fisica

Sapienza Università di Roma
P.le A. Moro, 5
I - 00185 ROMA, Italy
tel.: +39 06 4991 4 254
fax: +39 06 4454992
email: segreteria@icra.it

Thursday May 30, 2013 - 4,00 pm

Aula Conversi (Physics Dept., Old Building - 1st Floor)

Physics Dept./ICRA joint Seminar

Speaker: Dr. Federico SEMBOLINI

Institution: Universidad Autonoma de Madrid (Spain)/Università "Sapienza" di Roma (Italy)

Title: Exploring the properties of galaxy clusters with hydrodynamicalsimulations: the MUSIC dataset.

Abstract:

I will introduce the MUSIC dataset (Marenostrum-MUltiDark Simultations of galaxy Clusters) - presently the largest sample of hydrodynamically simulated galaxy clusters, comprised of more than 700 clusters and 2000 groups. The analysis of the baryon content (gas and stars) of the most massive clusters of the MUSIC dataset, performed as a function of aperture radius and redshift, is compared with the most recent observational estimates of the gas fraction in galaxy clusters, showing a good agreement when the effects of cooling and stellar feedbacks are included. I will also present a detailed analysis of the scaling relations of the thermal SZ (Sunyaev-Zel'dovich) effect derived from MUSIC clusters. The integrated SZ brightness, Y, is one of the best observational proxies used to infer the total cluster mass, M, as SZ observations allow exploration of regions of clusters not reachable by present X-ray experiments. A possible redshift dependence on the Y-M scaling relatio, extending the analysis to protoclusters, objects typically at redshift higher than 1, is studied. The analysis of the scaling relations of MUSIC clusters is completed by estimating the X-ray properties of the objects using PHOX, in order to explore the relationship between galaxy clusters properties with different observational approaches, as the X-band is considered to be the observational counterpart of the SZ effect.