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

The Evolution of the High-z Galaxy Populations

Jerusalem 2004

Hans-Walter Rix - MPIA


The evolution of the cosmic star formation rate

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


First 1996 1997 estimates of the cosmic star formation history

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 version giavalisco et al 2003 goods

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


And from the perspective of sub mm thermal dust emission

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


The evolution of intense starbursts

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

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

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 mass step 1

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


Mean color of the galaxy population as a function of redshift

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 mass rudnick et al 2003

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

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

Example: Red Galaxies in the Hubble Deep Field

Jerusalem 2004

Hans-Walter Rix - MPIA


The evolution of the high z galaxy populations

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

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


The evolution of the high z galaxy populations

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

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

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


Are there large disk galaxies at high redshift labbe et al 2003 see also lowenthal et al 1997

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

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


Size evolution from goods ferguson et al 2003

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


Can one map the evolution of size at a given stellar mass fires trujillo et al 2003

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


What if the sdss galaxies were observed at 1 z 3 in fires

  • 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 fires1

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

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

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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