Star-formation histories Sorour Shamshiri with Peter Thomas and thanks to Bruno Henriques Rita Tojiero Star- Formation Histories Outline: VESPA What is VESPA What is the result? Evolution of star-formation history time-bins Comparison SFH between SAMs and VESPA For different redshits Conclusions What is VESPA • An analysis to the Sloan Digital Sky Survey final spectroscopic data release of MGS and LRG sample. • The result is a catalogue of star formation and metallicity histories, dust content and stellar masses of nearly 800,000 galaxies. • VESPA is intrinsically model dependent, including the SSP modeling, IMF or dust modeling. Method • VESPA solves the following problem: • Sλ(t,Z) is the luminosity per unit wavelength of a single stellar population of age t and metallicity Z, per unit mass . VESPA’s bins • In HR bin, it is assumed a constant star formation rate • For low-resolution , a decaying star formation history is used. Model • Initial mass function – BC03 models: a Chabrier initial mass function – Maraston (M05): with a Kroupa initial mass function • Dust model: – One_parameter – Two_parameter TBC= 0.03Gyr VESPA: BC03 vs M05 VESPA: dust models L-Galaxies: evolution of star-formation history time-bins Picture credit: Rob Yates Comparison of models with VESPA SFH for different redshifts Conclusions • We presented Star-Formation Histories for two different versions of the L-Galaxies SA model and compared them with observations from VESPA. • The Guo11 and HWT12 models bracket the VESPA results: HWT12 forms fewer stars at early times (ie high redshift) but a higher starformation rate at all subsequent times.