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OATS-UNI/TS SEMINAR
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Speaker: Antonio Pipino (Institut fur Astronomie - ETH Zurich)

Title: Specific star formation rate, quenching and the evolution of the galaxies over cosmic time
Date: Wednesday, March 21th, 2012
Time: 11:30
Venue: Villa Bazzoni
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Abstract: In this talk I revisit current issues in semi-analytic models by comparing the predictions by GalICS to the latest observations of the galaxy color (bimodality), the passive fraction in groups , as well as to the galaxy mass function and the specific star formation rate (sSFR) evolution over cosmic time. In particular, I explore a range of star formation prescriptions and (halo- versus stellar mass-) quenching models. "Standard" models predict an excess of red, passive and alpha-enhanced population (satellite) galaxies at masses ~ 1E10 Msun. Whilst both the halo- and the mass-quenching models broadly match the present-day mass functions, a disagreement with data becomes evident at high redshift, in terms of a lack of massive galaxies and an excess of lower mass objects. At lower masses the models predict an excess of (passive) galaxies, as well as a milder evolution at z smaller than 2 in the number density, at variance with observations and irrespective of the adopted quenching model. A better match is achieved by empirically forcing the model galaxies to obey to the observed sSFR evolution. This empirical solution brings the predicted passive-fraction and the colors in better agreement with data and suggests that many of the current problems in semi-analytic models are rooted in the prescriptions for the gas accretion/cooling and the star formation.
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Contact: Francesca Matteucci (DAUT)