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High Redshift Starbursts Mauro Giavalisco Space Telescope Science Institute and the GOODS team STScI/ESO/ST-ECF/JPL/SSC/Gemini/Boston U./U. Ariz./U. Fla./U. Hawai/UCLA/UCSC/IAP/Saclay/Yale/AUI The Quest for the Early Galaxies GOODS: Great Observatories Origins Deep Survey Giavalisco 2002 ARA&A Ellis 1997 ARA&A During the mid-90’s, with improved instrumentation, the commissioning of the 8-m class telescopes, and the repair of HST, a number of influential deep galaxy surveys (CFRS, LBGS, HDF) uncovered two important pieces of evidence: 1. Normal, luminous galaxies (the bright end of the Hubble sequence) were essentially in place by z~1 2. Massive (M*) galaxies formed prior to z~1 The universe was well populated with star-forming galaxies at z~3 At z~1 these must be old and/or massive or both. Are these the progenitors of the bright galaxies? Earlier suggestions that the bulk of galaxies formation occurred at z<1 and that “essentially no galaxies are to be expected at redshifts z>1” (1993, actual quote) were dismissed. GOODS: Great Observatories Origins Deep Survey Lilly et al. 1995 Abraham et al. 1996 GOODS: Great Observatories Origins Deep Survey Star-forming galaxies at z~3 (Lyman Break Galaxiess) Steidel, Giavalisco, Dickinson, Pettini & Adelberger 1996 Efficient star formation at z>2.5 GOODS: Great Observatories Origins Deep Survey Steidel, Adelberger, Giavalisco, Dickinson & Pettini 1999 GOODS: Great Observatories Origins Deep Survey Galaxy morphology at z~3 •Smaller •Regulars, •Irregulars, •Merging, •Spheroids? •Disks? •No Hubble Seq. •No l-dependence Giavalisco et al. 1994; Giavalisco et al. 1996; Steidel, Giavalisco, Dickinson & Adelberger 1996; Lowenthal et al. 1997; Dickinson 1998; Giavalisco 1998; Papovich, Giavalisco, Dickinson, Conselice & Ferguson 2003 Papovich, Dickinson, Giavalisco, Conselice & Ferguson 2004 GOODS: Great Observatories Origins Deep Survey Some rates are relatively low, ~ today’s spirals; others are prodigiously high Metallicity ~1/10 to ~ solar Still an open issue UV-star formation rates GOODS: Great Observatories Origins Deep Survey The birth of the GOODS • No Hubble Sequence apparently observed at z>2. When and how did it form? • What kind of galaxies are LBGs – Bursting dwarfs? Massive? – What did they evolve into? How much stellar mass did they contribute? – Up to which redshift are there LBGs? When did SF on galactic scale start? • Are there other (non LBG selectable, I.e. non starforming or very obscured) galaxies at z>2? • How does star formation occur and evolve? GOODS: Great Observatories Origins Deep Survey The GOODS Treasury/Legacy Mission Aim: to establish deep reference fields with public data sets from X-ray through radio wavelengths for the study of galaxy and AGN evolution of the broadest accessible range of redshift and cosmic time. GOODS unites the deepest survey data from NASA’s Great Observatories (HST, Chandra, SIRTF), ESA’s XMM-Newton, and the great ground-based observatories. Primary science goals: • • • • • The star formation and mass assembly history of galaxies The growth distribution of dark matter structures Supernovae at high redshifts and the cosmic expansion Census of energetic output from star formation and supermassive black holes Measurements or limits on the discrete source component of the EBL Raw data public upon acquisition; reduced data released as soon as possible A Synopsis of GOODS GOODS: Great Observatories Origins Deep Survey GOODS Space GOODS Ground • • HST Treasury (PI: M. Giavalisco) – B, V, i, z (3, 2.5, 2.5, 5 orbits) – 400 orbits – Δθ = 0.05 arcsec, or ~0.3 kpc at 0.5<z<5 – 0.1 sq.degree – 45 days cadence for Type Ie Sne at z~1 • SIRTF Legacy (PI: M. Dickinson) – 3.6, 4.5, 5.8, 8, 24 μm – 576 hr – 0.1 sq.degree • • Chandra (archival): – 0.5 to 8 KeV – Δθ < 1 arcsec on axis XMM-Newton (archival) ESO, institutional partner (PI C. Cesarsky), CDF-S – – • Keck, access through GOODS’ CoIs – • • • Very deep U-band imaging Gemini – – • Large-area BVRI imaging NOAO support to Legacy & Treasury – • Deep spectroscopic coverage Subaru, access through GOODS’ CoI – • Full spectroscopic coverage in CDF-S Ancillary optical and near-IR imaging Optical spectroscopy, HDF-N Near-IR spectroscopy, HDF-S ATCA, ultra deep (5-10 mJy) 3-20 cm imaging, of CDF-S VLA, ultra deep HDF-N (+Merlin, WSRT) JCMT + SCUBA sub-mm maps of HDF-N GOODS: Great Observatories Origins Deep Survey GOODS/ACS B = 27.5 GOODS: Great Observatories Origins Deep Survey V = 27.9 i = 27.0 ∆m ~ 0.3-0.6 AB mag; S/N=10 Diffuse source, 0.5” diameter Add ~ 0.9 mag for stellar sources HDF/WFPC2 B = 27.9 V = 28.2 I = 27.6 z = 26.7 In ~2-3 months we will release a new stack of ~15 orbits in the z band, as well as ~50% and ~30% more exp. time in the i and V bands, in both fields, plus source catalogs (GOODS++) GOODS: Great Observatories Origins Deep Survey •Theory predicts that dark matter structures form at z~20-30 •It does not clearly predict galaxies, because we do not fully understand star formation GOODS galaxies at High Redshift B435 V606 i775 z850 Unattenuated Spectrum Spectrum Attenuated by IGM z~4 •Empirical information on galaxy evolution needed to the highest redshifts •GOODS yielded the deepest and largest quality samples of LBGs at z~4 to ~6 B435 V606 z850 GOODS: Great Observatories Origins Deep Survey B-dropouts, z~4 LBG color selection V-dropouts, z~5 Galaxies at z~6 GOODS: Great Observatories Origins Deep Survey Dickinson et al. 2003 (~6.8% of the cosmic age) ACS/grism, Keck/LRIS & VLT/FORS2 observations confirm z=5.83 S123 #5144: m(z) = 25.3 Observed redshift distribution GOODS: Great Observatories Origins Deep Survey #24 Z=5.78 Z=6.24? Curves from full numerical simulations Giavalisco et al. 2004, 2005 V Z=5.83 Spectra from Bunker et al. 2003; Stanway et al. 2003; Vanzella et al. 2004 and the GOODS Team GOODS: Great Observatories Origins Deep Survey LBG luminosity function Apparently, very little evolution in the UV luminosity function GOODS: Great Observatories Origins Deep Survey The history of the cosmic star formation activity: We find that at z~6 the cosmic star formation activity was nearly as vigorous as it was at its peak, between z~2 and z~3. NOTE: soon, nearly all GOODS will have three times the original exposure time in z band, and ~50% more in i band (thanks to the Sne program). Measure at z~6 will significantly improve. a=-1.6 assumed Giavalisco et al. 2004 Giavalisco et al. 2005, in prep. GOODS: Great Observatories Origins Deep Survey Still uncertainty on measures •LF still not well constrained •Clean z~6 color selection still missing •Cosmic variance still not understood •Will use SST data to refine z~6 sample •Will triple exp time in GOODS See also Bunker et al. 2004 Bouwens et al. 2004 GOODS: Great Observatories Origins Deep Survey SFR from X-ray emission Lehmert et al 2005 See also Giavalisco 2002, ARA&A GOODS: Great Observatories Origins Deep Survey Dust obscuration correction: Calzetti starburst obscuration law B&C synthetic SED Similar to what observed at z~3 Star formation rates z~4 B-band dropouts SIRTF Imaging GOODS: Great Observatories Origins Deep Survey GOODS sensitivity 5-σ limiting flux μJy 5-σ limiting AB mag 0.11 26.3 0.21 25.6 1.35 23.6 1.66 23.4 20.0 20.7 Stellar mass & star formation GOODS: Great Observatories Origins Deep Survey Mass: Rest-frame near-IR (e.g., rest-frame K-band at z~3), provides best photometric measure of total stellar content Reduces range of M/L(l) for different stellar populations Minimizes effects of dust obscuration Star formation: Use many independent indicators for to calibrate star formation (obscured & open) in “ordinary” starbursts (e.g. LBGs) at z > 2. • mid- to far-IR (SIRTF/MIPS); rest-frame UV (e.g, U-band); radio (VLA, ATCA); sub-mm (SCUBA, SEST); nebular lines (spectroscopy) PAH + continuum (24 mm) Optical + near-IR + nebular lines Stellar mass fitting UV Far IR (GTO) Measuring star formation GOODS: Great Observatories Origins Deep Survey Rest-optical & -IR at z~6 • SST IRAC detections of z~6 galaxies => stellar population & dust fitting possible ch1, 3.6mm lrest=5300A ch2, 4.5mm lrest=6600A Dickinson et al in prep GOODS: Great Observatories Origins Deep Survey U- and B- dropouts have similar UV-Optical color-magnitude "trends”. Rest-frame UV luminosity density roughly comparable at z ~ 3 and 4. Increase of ~33% in the restframe B-band luminosity density from z ~ 4 to 3. UV-Optical color reddens from z ~ 4 to 3, which implies an increase in the stellar-mass/light ratio. Suggests that the stellar mass is increasing by > 33% growth in B- Luminosity Density versus Color and Redshift Papovich et al. 2003 increase of ~33% Implications for Galaxy Evolution GOODS: Great Observatories Origins Deep Survey Dickinson, Papovich, Ferguson, & Budavari 2003 Implications for Galaxy Evolution GOODS: Great Observatories Origins Deep Survey Dickinson, Papovich, Ferguson, & Budavari 2003 Stellar mass is building up We still need to know how this growth depends on the total mass Total mass of individual galaxies seems to evolve less rapidly: bottles form first, wine is added later GOODS; Papovich et al. 2004 Morphology of Lyman Break Galaxies at z~4 GOODS: Great Observatories Origins Deep Survey Sersic profile fits and Sersic indices: [Ravindranath et al. 2005] Irregulars: (n < 0.5) Disks: (0.5 > n > 1.0) Morphology of Lyman Break Galaxies at z~4 GOODS: Great Observatories Origins Deep Survey Bulges (n > 3.0) Central compact component / point sources? (n = 5.0) LBG morphology: light profiles GOODS: Great Observatories Origins Deep Survey We measured the light profiles and parametrized them with the Sersic index Ravindranath et al. 2005 GOODS: Great Observatories Origins Deep Survey Morphology of LBG Theory predicts that when they form undisturbed, galaxies are disks. Images show a distribution of morphology. Both spheroid-like and disk-like morphology are observed. z=0 disks z=0 spheroids Ravindranath et al. 2005 GOODS: Great Observatories Origins Deep Survey Morphology of LBG: the GINI and M20 coefficients mergers spheroids Both spheroids and disk, as well as “transitional morphologies, observed. Major mergers estimated at 15-25%, both at z~4 and z~1.4 (in agreement with kinematics of close pairs with DEIMOS-DEEP –Lin et al. 2005) Lotz, Madau, Giavalisco, Conselice & Ferguson 2005 Local galaxies at high redshift GOODS: Great Observatories Origins Deep Survey Statistics calibrated using local galaxies Lotz et al. 2005 GOODS: Great Observatories Origins Deep Survey Lotz et al. 2005 LBG morphology GOODS: Great Observatories Origins Deep Survey Lotz et al. 2005 LBG morphology GOODS: Great Observatories Origins Deep Survey Lotz et al. 2005 LBG morphology GOODS: Great Observatories Origins Deep Survey WFPC2 (HDF) and NIC3 J and H images Internal color dispersion consistent with relatively young and homogeneous stellar population Dickinson 1998 Papovich, Giavalisco, Dickinson, Conselice & Ferguson 2004 Papovich, Dickinson, Giavalisco Conselice & Ferguson 2004 Infrequent “morphological k-correction” GOODS: Great Observatories Origins Deep Survey The Evolution of galaxy size First measures at these redshifts Testing key tenets of the theory Galaxies appear to grow hierarchically R~H(z)-2/3 Standard ruler Ferguson et al. 2003 R~H(z)-1 GOODS: Great Observatories Origins Deep Survey Galaxy Clustering at High Redshift • Galaxies at high redshifts have “strong” spatial clustering, I.e. they are more clustered than the z~0 halos “de-evolved back” at their redshift. – High-redshift galaxies are biased, I.e. they occupy only the most massive portion of the mass spectrum (today, the bias of the mix is b~1). • Important: – evolution of clustering with redshift contains information on how the mass spectrum gets populated with galaxies as the cosmic time goes on. – Clustering of star-forming galaxies contains information on relationship between mass and star formation activity GOODS: Great Observatories Origins Deep Survey Giavalisco et al. 1998 Clustering of starforming galaxies at z~3 r0=3.3+/- 0.3 Mpc h-1 g = -1.8 +/- 0.15 Steidel et al. 2003 Adelberger et al. 1998 Strong clustering, massive halos GOODS: Great Observatories Origins Deep Survey g=1.55 r0 =3.6 Mpc h-1 Porciani & Giavalisco 2002 Adelberger et al. 2004 GOODS: Great Observatories Origins Deep Survey local galaxies m*>2.5E10 MO m*>1.0E11 MO LBGs K20 EROs sub-mm SDSS QSOs Somerville 2004 GOODS: Great Observatories Origins Deep Survey Clustering segregation mass drives LUV (SFR) GOODS Ground Lee et al. 2005 Adelberger et al. (1998, 2004) Giavalisco et al. (1998) Giavalisco & Dickinson (2001) GOODS: Great Observatories Origins Deep Survey Clustering segregation at z~4 and 5 Clustering segregation is detected In the GOODS ACS sample at z~4 Consistent with other measures, e.g. Ouchi et al. 2004 Lee et al. 2005 GOODS: Great Observatories Origins Deep Survey We are observing the structure within the halo. Break observed at ~10 arcsec Note: 10 arcsec at z~4 is about ~350 kpc. See also Hamana et al. 2004 Lee et al. 2005 Halo sub-structure at z~4 GOODS: Great Observatories Origins Deep Survey The Halo Occupation Distribution at z~4 Consistent with Hamana et al. 2004 and Bullock et al. 2001 <Ng>=(M/M1)a M>Mmin Lee et al. 2005 1-s 2-s GOODS: Great Observatories Origins Deep Survey a = 0.89 +/- 0.05 M1 = (4.74 +/- 0.50) x 1013 MO Mmin = 6.10 x 1012 MO From SDSS data Zehavi et al. 2004 The Halo Occupation Distribution at z~0 GOODS: Great Observatories Origins Deep Survey Halo substructure: we observe an excess of faint galaxies around bright ones. massive halos contain more than one LBG “Bright Centers”: z_850<24.0 “Faint centers”: 24.0< z_850 <24.7 “Satellites”: z_850 >25.0 Lee et al. 2005 Halos and Galaxies at z~3-5 GOODS: Great Observatories Origins Deep Survey Halos and Galaxies at z~3-5 Clustering scaling in good agreement with hierarchical theory Implied halo mass in the range 5x1010 – 1012 MO 1-σ scatter between mass and SFR smaller that 100% Giavalisco & Dickinson 2001 Porciani & Giavalisco 2002 Lee et al. 2004, in prep. GOODS: Great Observatories Origins Deep Survey EROs, or UV-faint galaxies at z~2-3 Galaxies selected from near-IR photometry [(J-K)>2.3] A fraction would NOT be selected by LBG criteria (UV selection) However, overlap with LBG not quantified and likely significant (see Adelberger et al. 2004). They appear in general more evolved, I.e. more massive (larger clustering), with larger stellar mass, more metal rich, and more dust obscured) than LBGs. Occurrence of AGN also seems higher. At z~3 these galaxies have about 50% of the volume density of LBGs (highly uncertaint). However; they possibly contribute about up to 100% of the LBG stellar mass density, because they have higher M/L ratios Van Dokkum et al. 2004 GOODS: Great Observatories Origins Deep Survey Ks< 22, R-Ks>3.35 Moustakas et al. 2004 EROs EROs GOODS: Great Observatories Origins Deep Survey •ACS resolution is crucial to understand the nature of EROs •Broad-band SED or statistical morphology cannot discriminate •Evidence of massive galaxies at z~1.2-1.5 Moustakas et al. 2004 GOODS: Great Observatories Origins Deep Survey Yan et al. 2004 HUDF/GOODS EROs GOODS: Great Observatories Origins Deep Survey HUDF/GOODS EROs Uses HUDF plus GOODS-SST data SED fitting disfavour very dust obscured, star-forming galaxies SED better reproduced by a two-component composite populations: an old, evolved one, plus a low-intensity star-forming one. Stellar mass relatively large: 1010 – 1011 MO Evidence that similar objects exist at z~7 (Mobasher et al. 2005) Yan et al. 2004 GOODS: Great Observatories Origins Deep Survey Evidence of large stellar mass at z~5, 6 Yan et al. 2005 LBGs at z~5 and 6 GOODS: Great Observatories Origins Deep Survey Evidence of large stellar mass at z~5, 6 Yan et al. 2005 LBGs at z~5 and 6 GOODS: Great Observatories Origins Deep Survey An evolved, massive galaxy at z~7? HUDF + GOODS-SST Mobasher et al. 2005, submitted to Nature GOODS: Great Observatories Origins Deep Survey NIR-selected galaxies NIR selected galaxies with K<20 VLT FORS spectra SED fits show Mstar >1011 MO Claims that NIR selection yields more massive galaxies than UV selection Daddi et al. 2004 GOODS: Great Observatories Origins Deep Survey Near-IR selection picks up the high-end of the distribution of masses (total and stellar) Adelberger et al. 2004 Different populations? Galaxies at z~1-0 GOODS: Great Observatories Origins Deep Survey Cosmic variance Evolution of the integrated mass density, M>1011 MO GOODS data Little evolution in the stellar mass density from z~1 to today Note that at z~1 spirals dominated stellar mass density; the opposite at z~0: morphology transformation Bundy, Ellis & Conselice 2005 Today’s stellar mass density Ravindranath et al. 2003 –Sersic indices n<2 –Rest-frame MB <-19.5 –Photometric redshifts GOODS: Great Observatories Origins Deep Survey Disk galaxy evolution from GOODS Ravindranath et al. 2003 Number-densities are relatively constant to z~1 Tendency for smaller sizes at z~1 (30% smaller) The evolutionary link? GOODS: Great Observatories Origins Deep Survey The expected evolution of clustering (correlation length) suggests what the high redshift galaxies might evolve into at later epochs. Giavalisco, 2002 ARA&A Adelberger et al. 2004 GOODS: Great Observatories Origins Deep Survey Summary • GOODS exploring fundamental issues of cosmic origins • Large-scale star formation in place at less than ~7% of the cosmic time: – SF galaxies observed to at least up z~7 – Massive galaxy started very early in the cosmic evolution • Cosmic star formation (as traced by UV light) varies mildly at 3<z<6 – Universe is ~ as prolific a star former at z~6 as it is at z~3, after triplicating age – Unclear proportion of obscured and evolved galaxies – Obscured SF might contribute up to 100% of stellar mass density and star formation (2x) • SF galaxies seem already diversified at z~4. “Evolved” galaxies up to z~7? – Morphology mix includes spheroids, disks; 14-25% mergers at z~1.4-5 • • • • Direct evidence of growth of stellar mass from z~4 to z~1. Galaxies get smaller at z>1; size evolution consistent with hierarchical growth Massive galaxies in place at z~1; some galaxies are massive at z~2-3 Spatial clustering key to study relationship of star formation and dark matter: – – – – Evidence of halo sub-structure at z~4. Transition at r~1 Mpc; Mmin~109 MO Spatial clustering depends on UV luminosity, decreases for fainter galaxies More massive halos host more star formation; scaling consistent with CDM spectrum Implies relatively large total masses: 5x1010 – 1012 MO