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.