A Prescription for High-Redshift star formation

Alexander (Sasha) MuratovUniversity of Michigan

Advisor: Oleg Gnedin

Star Formation History of The Universe

Madau et al. 1996

State of Simulations

• Collisionless dark matter simulations can be run with great resolution down to zero redshift, but what are the stars and gas doing?

Kravtsov et al. (2004)

Prescriptive Model: Advantages

All quantities available at all times Made to be consistent with observations and

simulations Can provide insight into global processes on

different scales: Star Formation. Makes testable predictions. Disadvantages: makes testable predictions – need to

match many data sets. Sometimes difficult to constrain.

Observed fitsM

*-M

h relation (Woo et al. 2008)

logVc = -0.5 + .27logM* , M

* ~ Vc

3.8

Vc = V

max * 2½

Mh ~ V

max3.3

M*-Mgas relation (McGaugh 2005)

Mass metallicity relation: Woo et al. (2008)

Ms(z=0) = 109.6 MꙨ

Observed fits 2 – time evolution Dave & Oppenheimer

(2007).3 dex lower over 10 Gyr

Conroy & Wechsler (2008)Well fit by M

* ~ (1+z)-2

Equations again

• Mass

MW = 5.5 * 10^10 Solar (M*)

MW = 1 * 10^10 Solar (Mgas)

• Metallicity:

extra constraints:

fgas(z, M)

Anchored by GC's

• DM halos from Kravtsov et al. (2004)

• Hydro constraints from Kravtsov & Gnedin (2005)

• Bimodal metallicity distribution! (Muratov & Gnedin, in prep)

• KS Probablity: 51%

prediction for stellar fraction in dwarf galaxies

• M* = -1.85 + 1.03*Mh

• RMS: 0.212

• Red Line : Andrey Kravtsov's relation (2009)

• Different techniques used: instead of matching brightest to most massive, we apply direct relations.

• Which is right?

Summary

• We present a prescriptive model for baryonic mass and metallicity as a function of time and halo mass.

• Applying this prescription to DM simulations, we have studied GC formation.

• We also obtain a fit for MW Dwarfs. Produces a different result from Kravtsov 2009, Busha 2009.