Star-formation histories
Sorour Shamshiriwith Peter Thomasand thanks to
Bruno HenriquesRita 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 star-formation rate at all subsequent times.