1 + z

SF

R (

Msu

n y

r-1 M

pc-3

)

Hopkins 2004

Evolution of SFR density with redshift, using a common obscuration correction where necessary. The points are color-coded by rest-frame wavelength as follows: Blue: UV; green: [O II]; red: H   and H  ; pink: X-ray, FIR, submillimeter, and radio. The solid line shows the evolving 1.4 GHz LF derived by

Haarsma et al. (2000). The dot-dashed line shows the least-squares fit to all the z < 1 data points, log(  *)

= 3.10 log(1 + z) - 1.80. The dotted lines show pure luminosity evolution for the Condon (1989

) 1.4 GHz LF, at rates of Q = 2.5 (lower dotted line) and Q = 4.1 (upper dotted line). The dashed line

shows the "fossil" record from Local Group galaxies (Hopkins et al. 2001b).

Importance of High z DataImportance of High z Data•Now introduce three key 1 < z < 4 galaxy populations whose studies are relevant to addressing these issues – complementary!!

I: Lyman break galaxies: color-selected luminous star forming galaxies z > 2

II: Sub-mm galaxies located via redshifted dust emission

III: Various categories of “passively-evolving” sources whose selection has been enabled via deep IR data (BETTER: DRG=Distant

Red Galaxies, or EROs = Extremely Red Objects)

(TABELLA -- say ARAA)

Finding star-forming galaxies at high zFinding star-forming galaxies at high z

The Lyman continuum discontinuity is particularly powerful for isolating star-forming high redshift galaxies.

From the ground, we have access to the redshift range z=2.5-6 in the 0.3-1 micron range.

Steidel et al 1999 Ap J 462, L17 Steidel et al 1999 Ap J 519, 1Steidel et al 2003 Ap J 592 728

Steidel et al. 2003

Photometrically selected using rest frame UV colors – originally, z=2.7-3.4

Lyman break galaxies (U-band dropouts)High-z example:

(list of bands)

Photometric Cuts: Prediction and PracticePhotometric Cuts: Prediction and Practice

Expectations Real Data (10’ field)

Spectral energy distributions allow us to predict where distant SF galaxies lie in color-color diagrams such as (U-G vs G-R) (Steidel et al 1996)

Spectroscopic Confirmation at Keck

Giavalisco ARAA 2002

Dark shaded:

SFR calculated from UV luminosities without any dust correction

Light blue:

Corrected for dust assuming a continuous SF with age T=0.1Gyr and using the starburst obscuration law (E(B-V) derived from comparison observed and predicted colors

Light shaded:

Corrected for dust fitting broad-band photometry (UV to optical) with specphot. Models)

Lyman break galaxies (U-band dropouts)

Most well studied high-z galaxies:

HST images of spectroscopically-confirmed “Lyman break” galaxies with z>2 in Hubble Deep Field North revealing small physical scale-lengths and irregular morphologies

Giavalisco et al 1996 Ap J 470, 189

Extending the Technique 1 < z < 4 Extending the Technique 1 < z < 4

Lyman break

Balmer break

Kennicutt 1992

Elliptical

Sc

Sa

Sm/Irr

BEST INDICATOR IN THE OPTICAL:

THE Hα LINE (6563 A) IN EMISSION

THE ULTRAVOLET EMISSION AS INDICATOR OF ONGOING AND RECENT

STAR FORMATION

Leitherer and collaborators – STARBURST99

Extending the Technique 1 < z < 4 Extending the Technique 1 < z < 4

Lyman break

Balmer break

Sub-mm Star Forming SourcesSub-mm Star Forming Sources

SCUBA array15m JCMT

SCUBA: 850m array detects dusty star forming sources:- behind lensing clusters (Smail et al Ap J 490, L5, 1997) - in blind surveys (Hughes et al Nature 394, 211, 1998)

Source density implies 3 dex excess over no evolution model based on density of local IRAS sources:

Key question is what is the typical redshift, luminosity and SF rate?

Sub-mm astronomers

SUBMILLIMITER OBSERVATIONS

Sampling the IR emission with 850micron fluxes (e.g. Hughes et al. 1998) – Dust heated by either star formation or an active nucleus

Negative K-corrections – the flux density of a galaxy at ~800micron with fixed intrinsic luminosity is expected to be roughly constant at all redshifts 1 < z < 10

While the Lyman break technique prefentially selects UV-bright starbursts, the submillimiter emission best identifies IR luminous starbursts. The approaches are complementary (debated relation between the two poulations).

Radio Identification of Sub-mm SourcesRadio Identification of Sub-mm Sources

SCUBA sources often have no clear optical counterpart, so search with VLA & OVRO

L ~ 1013 L if z~2

Could be as important as the UV Lyman break population

Frayer et al (2000) AJ 120, 1668

Redshifts for radio-selected SCUBA sourcesRedshifts for radio-selected SCUBA sources

• VLA positions for 70% of f(850m) > 5 mJy (20% b/g)• Slits placed on radio positions (22 < I < 26.5) with Keck• 10-fold increase in number of SCUBA redshifts (LRIS-B)Chapman et al (2003) Nature 422, 695 Chapman et al (2005) Ap J 622, 722

• Most sub-mm sources have z < 4• Peak z = 2.4 – comparable to that for AGN • Although (LBG) 10 (SCUBA), luminosity/SF densities comparable: significant contribution to the star formation at high redshift

•Progenitors of ellipticals?

Sub-mm and Lyman break galaxies coevalSub-mm and Lyman break galaxies coeval

2003 2005

““Passively-Evolving” SourcesPassively-Evolving” Sources(wrong name!!!)(wrong name!!!)

for z ~ 1-2: select on I-H colour for z > 2: select on J-K colour

Such objects would not be seen in the Lyman break samples

LBGs and sub-mm are both star forming sources

Arrival of panoramic IR cameras opens possibility of locating non-SF (or dusty) galaxies at high z

Termed variously:

• Extremely Red Objects

• Distant Red Galaxies

depending on selection criterion (see McCarthy 2004 ARAA).

FIRES – VLT+ISAAC176 hours J,H,K imaging

MS1054-03N. Forster-Schreiber et al.5.4’ x 5.4’, seeing 0’’45

HDF SouthI. Labbe et al.2.4’ x 2.4’, seeing 0’’45

““Passively-Evolving” SourcesPassively-Evolving” Sources(wrong name!!!)(wrong name!!!)

for z ~ 1-2: select on I-H colour for z > 2: select on J-K colour

Such objects would not be seen in the Lyman break samples

LBGs and sub-mm are both star forming sources

Arrival of panoramic IR cameras opens possibility of locating non-SF (or dusty) galaxies at high z

Termed variously:

• Extremely Red Objects

• Distant Red Galaxies

depending on selection criterion (see McCarthy 2004 ARAA).

Kennicutt 1992

Elliptical

Sc

Sa

Sm/Irr

BEST INDICATOR IN THE OPTICAL:

THE Hα LINE (6563 A) IN EMISSION

THE ULTRAVOLET EMISSION AS INDICATOR OF ONGOING AND RECENT

STAR FORMATION

Leitherer and collaborators – STARBURST99

Z=2.43

Z=2.43

Z=2.43

Z=2.71

Z=3.52

Spectroscopy: not passively evolving!!Spectroscopy: not passively evolving!!

Objects with Objects with J-K J-K > 2.3> 2.3

Surprisingly high surface density:– ~0.8/arcmin to K=21 (two fields)– ~2/arcmin to K=22 (HDF-S)– ~3/arcmin to K=23 (HDF-S)

2

2

2

2

van Dokkum,Franx, Rix et al

Towards a Unified View of the Various High z PopulationsTowards a Unified View of the Various High z Populations

Integrating to produce a comoving cosmic SFH dodges the important question of the physical relevance of the seemingly diverse categories of high z galaxies (e.g. LBGs, sub-mm, DRGs).

Given they co-exist at 1<z<3 what is the relationship between these objects?

Key variables:

- basic physical properties (masses, SFRs, ages etc)

- relative contributions to SF rate at a given redshift

- degree of overlap (e.g. how many sub-mm sources are LBGs etc)

- spatial clustering

Some recent articles:

Papovich et al (2006)

Reddy et al (2005)

Lyman Break Galaxies - ClusteringLyman Break Galaxies - Clustering

UV bright galaxies at z~3 are clustered nearly as strongly as bright galaxies in the present Universe. Of what population are they the progenitors?

What are the masses of these galaxies (both dark and stellar)?

Adelberger et al (1998) demonstrated strong clustering of LBGs consistent with their hosting massive DM halos perhaps as progenitors of massive ellipticals (Baugh et al 1998)

(r) A(r r0)

V-band Luminosity Function at z~3V-band Luminosity Function at z~3Local LF

Shapley et al 2001 Ap J 562, 95

Key to physical nature of LBGs is origin of intense SF. Is it:

- prolonged due to formation at z~3 (Baugh et al 1998)

- temporary due to merger-induced star burst (Somerville et al 2001)

LBG Properties (z~3)LBG Properties (z~3) <age> = 320 Myr @ z = 3

<E(B-V)> =0.15 AUV~1.7 ~5

Shapley et al 2001 Ap J 562, 95

<SFR> ~ 45 M yr-1

<M*> = ~2 x 1010 M

Extinction correlates with age– young galaxies are much dustier

SFR for youngest galaxies average 275 M yr-1 ; oldest average 30 M yr-1 Objects with the highest SFRs are the dustiest objects

Composite Spectra: Young vs. OldComposite Spectra: Young vs. Old

• Young LBGs also have much weaker Ly emission, stronger interstellar absorption lines and redder spectral continua

• Galaxy-scale outflows (“superwinds”), with velocities ~500 kms s-1, are present in essentially every case examined in sufficient detail

LBG SummaryLBG Summary

• Period of elevated star formation (~100’s M yr-1) for ~50 Myr with large dust opacity (sub-mm galaxy overlap)

• Superwinds drive out both gas and dust, resulting in more quiescent star formation (10’s M yr-1) and smaller UV extinction

• Quiescent star formation phase lasts for at least a few hundred Myr; by end at least a few 1010 M of stars have formed

So how is this LBG-submm connection viewed from the sub-mm point of view?

What about clustering of sub-mm sources?What about clustering of sub-mm sources?

Blain et al 2004 Ap J 611, 725

Correlation length r0

Clustering allows us to determine the typical halo mass in which different galaxy types live

Evidence for stronger clustering than LBGs (though N=73 cf. N>1000 LBGs) suggesting more massive subset in dense structures

Daddi et al 2004 Ap J 617, 746

`BzK’ selection of passive `BzK’ selection of passive andand SF z>1.4 galaxies SF z>1.4 galaxies

New apparently less-biased technique for finding all galaxies 1.4<z<2.5

sBzK: star forming galaxies

pBzK: quiescent galaxies

(z-K)

(B-z) WHERE DO THESE FIT IN?

Reddy et al 2005 Ap J 633, 248

LBG & `BzK/SF’ z~2 populations are the same?LBG & `BzK/SF’ z~2 populations are the same?

Fraction of BzK/SF galaxies selected as LBGs and v.v.

(including X-ray AGN)

(excluding X-ray AGN)

Contribution to SF density

LBG

Spitzer Studies of Massive Red Galaxies (J-K>2.3)Spitzer Studies of Massive Red Galaxies (J-K>2.3)

Papovich et al 2006

K-selected sample of 153 DRGs z<3; many with M>1011 M ; 25% with AGN

Specific SFR (including IR dust emission) ~2.4 Gyr-1; >> than for z<1 galaxies

Witnessing bulk of SF in massive galaxies over 1.5<z<3

Stellar mass Specific SFR (/mass)

Implications of Cosmic SFHImplications of Cosmic SFHHopkins & Beacom (2006) – at z<1, SF density goes as (1+z)3.1

GALEX, SDSS UV

Spitzer FIR

ACS dropouts

Fitting parametric SFH can predict * (z) in absolute units

Cole et al 2dF

• Satisfactory agreement with local 2dF/2MASS mass density

• Data suggests half the local mass in stars is in place at z~2 0.2

• Major uncertainties are IMF and luminosity-dependent extinction

Star formation history Mass assembly history