From First Stars to (First) Galaxies

KAS16/MT Lecture IV - DarkLight2

KAS16/MT Lecture IV - DarkLight3

KAS16/MT Lecture IV - DarkLight4

KAS16/MT Lecture IV - DarkLight5

Smith et al. (2009)

n [cm-3]

T [K

]

KAS16/MT Lecture IV - DarkLight6

KAS16/MT Lecture IV - DarkLight

★Goal: Simplest meaningful model to understand evolution of galaxy formation

A model for galaxy formation

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★Galaxies form within dark-matter halos

•Working hypothesis: Dark matter halo assembly main driver of star formation

KAS16/MT Lecture IV - DarkLight

★L(Mh,z) depends on:

1. Stellar populations [young stars brighter]: Age(Mh,z)

2. Stellar mass: Mstar(Mh,z)

Our model for LF evolution

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★DM halos populated by galaxies with UV luminosity L(Mh,z)

L(Mh,z)~Mstar/Age [with constant star-formation history]

KAS16/MT Lecture IV - DarkLight

★Adopted galaxy “age”: DM halo assembly time

Galaxy ages

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★Rapid high-z assembly

★No free parameters

Mh/2 Mh

Halo assembly

time

Tacchella, Trenti & Carollo (2013) [MSc project]

KAS16/MT Lecture IV - DarkLight

★Minimal assumption: Stellar mass does not depend on redshift: Mstar(Mh,z)

From halo to stellar mass

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★Mstar(Mh) derived from single redshift calibration

Halo Mass [log Msun]

log(

Mst

ar/M

h)

KAS16/MT Lecture IV - DarkLight

★Minimal assumption: Stellar mass does not depend on redshift: Mstar(Mh,z)

From halo to stellar mass

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★Mstar(Mh) derived from single redshift calibration

Halo Mass [log Msun]

log(

Mst

ar/M

h)

★Luminosity defined at all z:

KAS16/MT Lecture IV - DarkLight

Luminosity function evolution

12Tacchella, Trenti & Carollo (2013) [MSc project]

KAS16/MT Lecture IV - DarkLight

Luminosity function evolution

13Tacchella, Trenti & Carollo (2013) [MSc project]

KAS16/MT Lecture IV - DarkLight

Luminosity function evolution

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★Model successful from z=0 to z=10!

★Assumptions validated!Tacchella, Trenti & Carollo (2013) [MSc project]

KAS16/MT Lecture IV - DarkLight

Luminosity function evolution

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★Validation from latest z~8-10 data

Mason, Trenti & Treu (2015)

★And predictions for z>10 [first 500 Myr]

KAS16/MT Lecture IV - DarkLight

Stellar mass density evolution

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★Modeling based on galaxy light only

★Yet… Evolution of stellar mass density described extremely well

★Further confirmation that basic model captures essence of galaxy evolution

Mason, Trenti & Treu (2015)

Observations

Predictions

KAS16/MT Lecture IV - DarkLight

Star formation history

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★Drivers of star formation:

★Halo mass function evolution (galaxy abundance)

★Halo assembly time (galaxy age)

More halos

Increased halo assembly time

Log

Star

form

atio

n ra

te [

Msu

n y

r -1

Mpc

-3]

Trenti et al. (2013)

KAS16/MT Lecture IV - DarkLight

Summary

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★Dark Matter halo assembly key driver of star formation

★Basic model reproduces the evolution of the star formation history

★Halos at fixed mass at different redshift have similar stellar mass, but different luminosities because galaxy ages change