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Seminars are organized jointly by the Trieste Astronomical Observatory (INAF/OATS) and the Astronomy Unit of the Physics Dept. of the Trieste University (UNI/TS). They usually take place on Wednesdays at 11:30, in the seminar room (Sala Ovale) of Villa Bazzoni in via Bazzoni 2, TS.

 

NEXT SEMINAR:

 

 

Mon, OCT 23, 2017 - EXTRA SEMINAR @ 15:30 
SPEAKER: Daniel Gruen (KIPAC/Stanford University, Stanford, CA, USA)
TITLE: Weak Lensing in the Dark Energy Survey

ABSTRACT: The Dark Energy Survey has combined analyses of galaxy clustering and weak gravitational lensing two-point correlation functions in its first year (Y1) of observations. The goal of this is to constrain cosmological parameters from lensing measurements of structure in the evolved Universe. The combination of two-point correlation functions provides information on the amplitude of density fluctuations (S8=0.794+0.029-0.027) and the dark energy equation of state (w=-0.80+0.20-0.22) that is competitive with Planck CMB data. When joint with probes of cosmic geometry, it yields the best measurement of these parameters to date. Besides reviewing these results and the technical advances that facilitated them, I will also give an outlook on upcoming work that provides a DES lensing view of higher than second moments of the matter density field.

contact: Mario Nonino

 

 

Wed, OCT 25, 2017
SPEAKER: Fabio Fontanot (INAF-OATS, Trieste, IT)
TITLE: Variations of the stellar initial mass function in semi-analytical models

ABSTRACT: I will discuss the implications of implementing a two independent variable Initial Mass Function (IMF) scenarios in semi-analytic models. These approaches provides a description of the dependence of the stellar IMF shape on the physical properties of model galaxies (either the SFR or the SFR surface density). In the framework of the GAEA (GAlaxy Evolution and Assembly) model, which features a detailed treatment of chemical enrichment and stellar feedback, I will show that realizations with a universal IMF predict a rather flat alpha/Fe-stellar mass relation. The models assuming a variable IMF, instead, are able to reproduce the observed increase of alpha-enhancement with stellar mass. This is mainly due to the fact that massive galaxies are characterized by larger star formation rates at high-redshift, leading to stronger alpha-enhancement with respect to low-mass galaxies. At the same time, the final stellar masses and mass-to-light-ratio of our model galaxies are larger than those estimated from the synthetic photometry assuming a universal IMF, providing a self-consistent interpretation of recent claims for IMF variations in massive galaxies, based on dynamical analysis of local early type galaxies. Indeed, the different variable IMF scenarios does not affect significantly the trend for shorter star formation timescales for more massive galaxies, but they can change significantly their star formation histories. Nonetheless, the definition of observational tests able to discriminate between these scenarios is challenging even for the next generation facilities.

contact: