“Artists can color the sky redbecause they know it’s blue.Those of us who aren’t artists must colorthings the way they are or people mightthink we’re stupid.”

Jules Feiffer

Red Galaxiesat

High Redshift

Stijn Wuyts, Marijn Franx, Pieter van Dokkum,Ivo Labbé, Natascha Förster Schreiber, Greg Rudnick,TJ Cox, Phil Hopkins, Brant Robertson, Lars Hernquist

• When did the stars in galaxies form?• How was the mass in galaxies assembled?

• When did the stars in galaxies form?• How was the mass in galaxies assembled?

Ingredients & History From colors to physics Evolution

Telescopes

Telescopes

Galaxy interactions

Galaxy interactions-simulations-

Galaxy interactions-simulations-

Holmberg 1941

Galaxy interactions-simulations-

Holmberg 1941 Springel et al.

Quasars&

Black Holes

Richards et al. 2005

Quasars

&

Black Holes

Schmidt 1963

2dF-SDSS LRG and QSO Survey

Genzel et al.

Quasars

&

Black Holes

Schmidt 1963

Häring & Rix 2004

Normal galaxies

Hubble 1926Hubble 1936

• HDFS (5 arcmin2)• MS 1054-03 (25 arcmin2)• CDFS (113 arcmin2)

Labbé et al. 2003

Normal galaxies

Hubble 1926Hubble 1936

• HDFS (5 arcmin2)• MS 1054-03 (25 arcmin2)• CDFS (113 arcmin2)

Stellar population synthesis

Wood 1966

Evolutionary stellar population synthesis

Bruzual & Charlot 2003

Evolutionary stellar population synthesis

Star formation historySSP, exponentially declining (τ300), CSF

Evolutionary stellar population synthesis

Dust screen (Calzetti et al. 2000)

SED modeling - results

Red galaxies at high redshift do not form a uniform population.

Red galaxies at high redshift dominate at the high mass end.

SED modeling - results

Red galaxies dominate the total IR emission at high redshift.

SED modeling - results

Testing SED modeling with simulations

• Wide range of spectral types• Have real universe equivalents

Testing SED modeling with simulations

Mismatch real vs. template SFH→ Impossible to correct for difference light- vs. mass-weighted

Impact of star formation history

Impact of dust

Increased extinction towards young stellar regionsreduces offset light- vs. mass-weighted properties.

Mismatch real vs. template SFH→ Impossible to correct for difference light- vs. mass-weighted→ Less severe in the presence of age-dependent extinction

Impact of dust

Intrinsic Attenuated

Every observer is limited by the light he/she receives.

Impact of dust

Eff

ectiv

e re

dden

ing

Effective extinction

Input: Calzetti, MW or SMC reddening curveEffective reddening: greyer than Calzetti

Impact of dust

Modeling sub-solar stellar populationswith solar-metallicity templates.→ underestimate reddening → underestimate extinction

Impact of metallicity

Real: Stars + AGN → Recovered: younger & dustier stellar pop.

Impact of AGN

Testing SED modeling with simulations: results

An evolutionary scenario

Sanders et al. 1988

ULIRG(L > 1012Lsun)

QSO

An evolutionary scenario

Hopkins et al. 2006

Quasar to galaxy demographics

Hopkins et al. 2006

Quasar to galaxy demographics

Hopkins et al. 2006

Abundance of massive galaxies

Mass function

Colors of massive galaxies

V-J

U-V

Colors of massive galaxies – by type

Colors of massive galaxies – by type

Selecting by specific star formation rate

Abundance of massive galaxies – by type

Pair statistics

Red Galaxiesat

High Redshift

Observations• Diversity at high redshift• Evolutionary scenario involving merger-triggered QSOs• Abundance of massive galaxies OK• Colors of dusty red galaxies not reproduced

Conclusions

Emlen 1967, 1970

After man, the indigo bunting is the best documented example of a speciesthat in its earthly life uses celestial bodies outside the solar system.

• When did the stars in galaxies form?• How was the mass in galaxies assembled?

Ingredients & History From colors to physics Evolution