1 + z SFR (M sun yr -1 Mpc -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) 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) b

Importance 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 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 micron range. Steidel et al 1999 Ap J 462, L17 Steidel et al 1999 Ap J 519, 1 Steidel et al 2003 Ap J

Steidel et al Photometrically selected using rest frame UV colors – originally, z= Lyman break galaxies (U-band dropouts)High-z example: (list of bands)

Photometric 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 Lyman break Balmer break

Kennicutt 1992 Elliptical Sc Sa Sm/Irr BEST INDICATOR IN THE OPTICAL: THE H α 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 Lyman break Balmer break

Sub-mm Star Forming Sources SCUBA array15m JCMT SCUBA: 850  m 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 Sources SCUBA sources often have no clear optical counterpart, so search with VLA & OVRO L ~ 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 sources VLA positions for 70% of f(850  m) > 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 coeval

“Passively-Evolving” Sources (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+ISAAC 176 hours J,H,K imaging MS N. Forster-Schreiber et al. 5.4’ x 5.4’, seeing 0’’45 HDF South I. Labbe et al. 2.4’ x 2.4’, seeing 0’’45

“Passively-Evolving” Sources (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 H α LINE (6563 A) IN EMISSION

THE ULTRAVOLET EMISSION AS INDICATOR OF ONGOING AND RECENT STAR FORMATION Leitherer and collaborators – STARBURST99

Z=2.43 Z=2.71 Z=3.52 Spectroscopy: not passively evolving!!

Objects with J-K > 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 van Dokkum,Franx, Rix et al

Towards 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 - 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)

V-band Luminosity Function at z~3 Local 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) = 320 z = 3 =0.15 A UV ~1.7  ~5 Shapley et al 2001 Ap J 562, 95 ~ 45 M  yr -1 = ~2 x 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. 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 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 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? Blain et al 2004 Ap J 611, 725 Correlation length r 0 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 and 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? 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) Papovich et al 2006 K-selected sample of 153 DRGs z 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 massSpecific SFR (/mass)

Implications of Cosmic SFH Hopkins & 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