The evolution of the high z galaxy populations
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The Evolution of the High-z Galaxy Populations. The Evolution of the Cosmic Star Formation Rate. When did it start / ramp up? When were half of the stars formed? Are we at the end of star-formation? Estimating the “cosmic star-formation rate” Estimating the SFRs in individual objects

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The Evolution of the High-z Galaxy Populations

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The Evolution of the High-z Galaxy Populations

Jerusalem 2004

Hans-Walter Rix - MPIA


The Evolution of the Cosmic Star Formation Rate

  • When did it start / ramp up?

  • When were half of the stars formed?

  • Are we at the end of star-formation?

  • Estimating the “cosmic star-formation rate”

    • Estimating the SFRs in individual objects

    • Are all relevant sources included

      • Faint

      • Obscured

Jerusalem 2004

Hans-Walter Rix - MPIA


The impact of LSS!

Steidel et al

HDF

(too “empty”)

First (1996-1997) estimates of the cosmic star-formation history

W=1!!

HDF

Lilly et al 1995

after Madau et al 1996

Warning: historical plots. Do not use for research!!

Jerusalem 2004

Hans-Walter Rix - MPIA


A current “UV-based” versionGiavalisco et al 2003 (GOODS)

after dust correction

from measured UVdensity

W=0.3 L=0.7 H0=70

Jerusalem 2004

Hans-Walter Rix - MPIA


Dust corrected UV (Giavalisco et al 03)

And from the perspective of sub-mm (thermal dust emission)

Completeness corrected x 11 (undetected sources)

thermal IR observed in sources

W=1

Barger et al 2000

Jerusalem 2004

Hans-Walter Rix - MPIA


Detected sources are likely to have luminosities ~ 5x Arp 220

SFR from ULIRGS now

The Evolution of Intense Starbursts

  • SFR from ULIRGs has dropped by > 100 since ~3!

  • NB: many high-z QSO’s also show enormous thermal dust emission  phases of intense SFR

Jerusalem 2004

Hans-Walter Rix - MPIA


Cosmic Star-Formation History: Upshot

  • <SFR> has risen by 5-7 x from z~0 to z~1.2

  • UV based estimates (after correction by 10) and sub-mm/thermal IR (after different correction of 10)

    give consistent <SFR> estimates 2<z<5

  • 1.5<z<5 <SFR> approximately constant (~2)

    (Note: there is some evidence for a drop beyond 5)

  • ULIRG (>few 100Msun/yr) mode of star-formation has dropped by >100 since z~3

Jerusalem 2004

Hans-Walter Rix - MPIA


Brief, but important aside

  • Galaxies with low SFR exist at 1<z<3.5

  • they can be found in IR-selected samples

  • They seem to make up ½ of the stellar mass (see below) at z~2-3

FIRES: van Dokkum et al 2003 with Spectra

Jerusalem 2004

Hans-Walter Rix - MPIA


The Build-Up of the Stellar MassStep 1

The mean color of galaxies as function of redshift (Rudnick et al 2003):

  • Optical colors  M/LB as long as star-formation history is not too “bursty” (Bell and de Jong 2001)

  • Individual galaxies may have bursts, but an ensemble of galaxies at a given epoch (say Dz~0.5) should not have their bursts all at the same time

  •  Look at the mean color of the galaxies as a function of

Jerusalem 2004

Hans-Walter Rix - MPIA


SFR ~ e-t/7Gyr since z~4-5

Mean Color of the Galaxy Population as a Function of Redshift

  • On average, galaxies were much bluer in the past

  • <M/L> was 10 x lower at z~3

 redshift

K-band selected sample (lrest>5000A)

x10 in M/L!

Jerusalem 2004

Hans-Walter Rix - MPIA


The Build-Up of Stellar MassRudnick et al 2003

  • Take IR-selected sample

  • Multiply jV with <M/L>V to get <r*>

  • ½ of stars since z~1.4

  • 50% between 2>z>1

  • 10% before z~3

Integrated SFR estimates (e.g. Giavalisco 03)

Big Bang

Now

Jerusalem 2004

Hans-Walter Rix - MPIA


Galaxy Clustering and its Evolution

  • Generic prediction of hierarchical CDM models:

    • More massive halos (=more luminous galaxies?) are more strongly clustered

    • (Luminous) Galaxies at early epochs are increasingly “biased”  their clustering remains high

  • Present epoch: redder galaxies are more clustered than blue ones

    • Has that always been true?

Jerusalem 2004

Hans-Walter Rix - MPIA


Example: Red Galaxies in the Hubble Deep Field

Jerusalem 2004

Hans-Walter Rix - MPIA


Jerusalem 2004

Hans-Walter Rix - MPIA

SUBARU Deep Field Ouchi et al 2002


Ly-break galaxies are observed to be clustered(e.g. Giavalisco et al 1998; Ouchi et al 2003)

Z~4 galaxies in the Subaru deep field

Jerusalem 2004

Hans-Walter Rix - MPIA


Correlation Length

S.A.M prediction

Kauffmann et al 99

Baugh et al 99

Bias

Ouchi et al 2003

Jerusalem 2004

Hans-Walter Rix - MPIA


How are galaxies and the IGM (=Ly-a forest) correlated?

  • Search for galaxies near the line of sight to a distant QSO

  • Is there an overabundance of neutral gas in the vicinity of galaxies at z~3?

  • Yes  Galaxies lived in large-scale overdense regions

??

 more HI

Distance LBG to Ly-a Absorption

Jerusalem 2004

Hans-Walter Rix - MPIA


Internal Structure of Early Galaxies

  • (Astro-)folklore:

    • High-z galaxies are compact

    • There are no big disks at high-z

  • Basis of that lore:

    • Observations (see below)

    • Theoretical expectation:

      • Halos that collapse early are denser

      • Spin parameter l is universal

      • Size of galaxies reflects angular momentum of halo

         baryons have less ang. Mom.  small galaxies

Jerusalem 2004

Hans-Walter Rix - MPIA


At the present, “normal” disk galaxies look completely different in the UV than in the optical

M81

“peculiar”, or star-forming ring seen in the UV

Older / redder bulge / bar?

Zspec=2.9

Are there large (disk?) galaxies at high redshift?(Labbe et al 2003; see also Lowenthal et al 1997)

Jerusalem 2004

Hans-Walter Rix - MPIA


Several examples in the HDF South

  • Can’t prove that these objects are disks, but they sure look like local examples

  • However, they are likely to be single entities that are not grossly disturbed

Jerusalem 2004

Hans-Walter Rix - MPIA


Rest-frame 1500A Size

Constant size

Increasing redshift 

Apparent size [“]

Size Evolutionfrom GOODS (Ferguson et al 2003)

  •  UV size at a given UV luminosity was smaller in the past

Jerusalem 2004

Hans-Walter Rix - MPIA


Size  Luminosity

Size  Mass (stellar)

SDSS z~0

Shen et al 2003

Can one map the evolution of size at a given (stellar) mass?(FIRES; Trujillo et al 2003)

  • What is the empirical null hypothesis?

Jerusalem 2004

Hans-Walter Rix - MPIA


  • Simulated distribution of sizes, assuming

    • SDSS size distribution holds high-z

    • same stellar mass as observed in FIRES

    • all observational effects

What if the SDSS Galaxies were observed at 1<z<3 in FIRES?

Jerusalem 2004

Hans-Walter Rix - MPIA


What if the SDSS Galaxies were observed at 1<z<3 in FIRES?

Actually observed in FIRES

Note: rest-frame V-band sizes at all z’s

Jerusalem 2004

Hans-Walter Rix - MPIA


Describing (the lack of) size evolution with redshift

  • Let’s assume that the SDSS distribution holds in its functional form at all redshifts, but that re(M*)~(1+z)a

  • Fit a from the FIRES data…

    At a given stellar mass, galaxies have the same size at all (observed) redshifts!

Re (z | Lv)

Re (z | M*)

Jerusalem 2004

Hans-Walter Rix - MPIA


Summary

  • Different approaches to dM*/dt(z) and M*(z) give (surprisingly?) consistent answers, at the ~2 x level.

    • We live at the end of star/galaxy formation

    • The epoch where most, say 80%, of the stars form has been identified: 3>z>0.5

    • No clear evidence for the “onset” of SF, yet.

  • Galaxies at high-z are observed to be highly clustered

    • They are “rarer” objects  bias

  • Galaxy sizes do not show the expected imprint of “formation epoch”

    • Re(M*)~ const. with z

Jerusalem 2004

Hans-Walter Rix - MPIA


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