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.