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High Redshift Starbursts
Mauro GiavaliscoSpace 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
GOODS: Great Observatories Origins Deep Survey
The Quest for the Early Galaxies
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 Massive (M*) galaxies formed prior to z~1
2. 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.
Giavalisco 2002 ARA&AEllis 1997 ARA&A
GOODS: Great Observatories Origins Deep Survey
Abraham et al. 1996
Lilly et al. 1995
GOODS: Great Observatories Origins Deep Survey
Star-forming galaxies at z~3 (Lyman Break Galaxiess)
Steidel, Giavalisco, Dickinson, Pettini & Adelberger 1996
GOODS: Great Observatories Origins Deep Survey
Efficient star formation at z>2.5
Steidel, Adelberger, Giavalisco, Dickinson & Pettini 1999
GOODS: Great Observatories Origins Deep Survey
Galaxy morphology at z~3
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 2003Papovich, Dickinson, Giavalisco, Conselice & Ferguson 2004
•Smaller•Regulars,•Irregulars,•Merging,•Spheroids?•Disks?•No Hubble Seq.•No -dependence
GOODS: Great Observatories Origins Deep Survey
UV-star formation rates
Some rates are relatively low, ~ today’s spirals;
others are prodigiously high
Metallicity ~1/10 to ~ solar
Still an open issue
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 star-forming 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
GOODS: Great Observatories Origins Deep Survey
A Synopsis of GOODS
GOODS Space• 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)
GOODS Ground• ESO, institutional partner (PI C. Cesarsky),
CDF-S– Full spectroscopic coverage in CDF-S
– Ancillary optical and near-IR imaging
• Keck, access through GOODS’ CoIs– Deep spectroscopic coverage
• Subaru, access through GOODS’ CoI– Large-area BVRI imaging
• NOAO support to Legacy & Treasury– Very deep U-band imaging
• Gemini– Optical spectroscopy, HDF-N
– Near-IR spectroscopy, HDF-S
• ATCA, ultra deep (5-10 Jy) 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: Great Observatories Origins Deep Survey
GOODS/ACS
B = 27.5
V = 27.9
i = 27.0
z = 26.7
∆m ~ 0.3-0.6
AB mag; S/N=10Diffuse source, 0.5” diameterAdd ~ 0.9 mag for stellar sources
HDF/WFPC2
B = 27.9
V = 28.2
I = 27.6
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
GOODS galaxies at High Redshift
•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
•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
Unattenuated Spectrum Spectrum
Attenuated by IGM
B435 V606 i775 z850
z~4
GOODS: Great Observatories Origins Deep Survey
LBG color selection
B-dropouts, z~4 V-dropouts, z~5
GOODS: Great Observatories Origins Deep Survey
Galaxies at z~6 (~6.8% of the cosmic age)
S123 #5144: m(z) = 25.3
ACS/grism, Keck/LRIS & VLT/FORS2 observations confirm z=5.83
Dickinson et al. 2003
GOODS: Great Observatories Origins Deep Survey
Observed redshift distribution
V
Z=5.78
Z=5.83
Z=6.24?
Spectra fromBunker et al. 2003;Stanway et al. 2003;Vanzella et al. 2004and the GOODS Team
Curves from fullnumerical simulationsGiavalisco et al. 2004, 2005
#24
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.
Giavalisco et al. 2004Giavalisco et al. 2005, in prep.
=-1.6 assumed
GOODS: Great Observatories Origins Deep Survey
Still uncertainty on measures
Bouwens et al. 2004
•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
GOODS: Great Observatories Origins Deep Survey
SFR from X-ray emission
Lehmert et al 2005See also Giavalisco 2002, ARA&A
GOODS: Great Observatories Origins Deep Survey
Star formation rates
Dust obscuration correction:
Calzetti starburst obscurationlaw
B&C synthetic SED
Similar to what observed at z~3
z~4 B-band dropouts
GOODS: Great Observatories Origins Deep Survey
SIRTF Imaging
GOODS sensitivity
0.1126.3
0.2125.6
1.3523.6
1.6623.4
20.020.7
5-σ limiting flux μJy5-σ limiting AB mag
GOODS: Great Observatories Origins Deep Survey
Stellar mass & star formation
PAH + continuum (24 m)
UV
Far IR(GTO)
Optical+ near-IR+ nebular lines
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() 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)
Stellar mass fitting
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
Dickinson et al in prep
ch1, 3.6mrest=5300A
ch2, 4.5mrest=6600A
GOODS: Great Observatories Origins Deep Survey
Luminosity Density versus Color and Redshift
increase of ~33%
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 rest-frame 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-band luminosity density.
Papovich et al. 2003
GOODS: Great Observatories Origins Deep Survey
Implications for Galaxy Evolution
Dickinson, Papovich, Ferguson, & Budavari 2003
GOODS: Great Observatories Origins Deep Survey
Implications for Galaxy Evolution
Dickinson, Papovich, Ferguson, & Budavari 2003
GOODS; Papovich et al. 2004
Stellar mass is building up
We still need to know how this growth depends on the total mass
Total mass of individualgalaxies seems to evolveless rapidly:bottles form first, wine is added later
GOODS: Great Observatories Origins Deep Survey
Morphology of Lyman Break Galaxies at z~4
Sersic profile fits and Sersic indices:
[Ravindranath et al. 2005]
Irregulars: (n < 0.5)
Disks: (0.5 > n > 1.0)
GOODS: Great Observatories Origins Deep Survey
Morphology of Lyman Break Galaxies at z~4
Bulges (n > 3.0)
Central compact component / point sources? (n = 5.0)
GOODS: Great Observatories Origins Deep Survey
LBG morphology: light profiles
Ravindranath et al. 2005
We measured the light profiles and parametrized them with the Sersic index
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 areobserved.
Ravindranath et al. 2005z=0 disksz=0 spheroids
GOODS: Great Observatories Origins Deep Survey
Morphology of LBG: the GINI and M20 coefficients
Lotz, Madau, Giavalisco, Conselice & Ferguson 2005
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)
mergers spheroids
GOODS: Great Observatories Origins Deep Survey
Local galaxies at high redshift
Statistics calibrated using local galaxies
Lotz et al. 2005
GOODS: Great Observatories Origins Deep Survey
LBG morphology
Lotz et al. 2005
GOODS: Great Observatories Origins Deep Survey
LBG morphology
Lotz et al. 2005
GOODS: Great Observatories Origins Deep Survey
LBG morphology
Lotz et al. 2005
GOODS: Great Observatories Origins Deep Survey
Infrequent “morphological k-correction”
Dickinson 1998
Papovich, Giavalisco, Dickinson, Conselice & Ferguson 2004
Papovich, Dickinson, GiavaliscoConselice & Ferguson 2004
WFPC2 (HDF) and NIC3 J and H images
Internal color dispersion consistent with relatively young and homogeneous stellar population
GOODS: Great Observatories Origins Deep Survey
The Evolution of galaxy size
Standard ruler
R~H(z)-2/3
R~H(z)-1
First measures at these redshiftsTesting key tenets of the theory
Galaxies appear to grow hierarchically
Ferguson et al. 2003
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
Clustering of star-forming galaxies at z~3
Giavalisco et al. 1998Steidel et al. 2003Adelberger et al. 1998
r0=3.3+/- 0.3 Mpc h-1
= -1.8 +/- 0.15
GOODS: Great Observatories Origins Deep Survey
Strong clustering, massive halos
Porciani & Giavalisco 2002 Adelberger et al. 2004
=1.55r0 =3.6 Mpc h-1
GOODS: Great Observatories Origins Deep Survey
local galaxiesm*>2.5E10 MO
m*>1.0E11 MO
EROs
sub-mm
K20
SDSS QSOs
LBGs
Somerville 2004
GOODS: Great Observatories Origins Deep Survey
Clustering segregationmass drives LUV (SFR)
Adelberger et al. (1998, 2004)Giavalisco et al. (1998)Giavalisco & Dickinson (2001)
GOODS Ground
Lee et al. 2005
GOODS: Great Observatories Origins Deep Survey
Clustering segregation at z~4 and 5
Lee et al. 2005
Clustering segregation is detected In the GOODS ACS sample at z~4
Consistent with other measures, e.g.Ouchi et al. 2004
GOODS: Great Observatories Origins Deep Survey
Halo sub-structure at z~4
Lee et al. 2005
We are observingthe structure withinthe halo.
Break observed at ~10 arcsec
Note: 10 arcsec at z~4 is about ~350 kpc.
See also Hamana et al. 2004
GOODS: Great Observatories Origins Deep Survey
The Halo Occupation Distribution at z~4
<Ng>=(M/M1)
M>Mmin
Lee et al. 2005
Consistent with Hamana et al. 2004and Bullock et al. 2001
2-1-
GOODS: Great Observatories Origins Deep Survey
The Halo Occupation Distribution at z~0
From SDSS dataZehavi et al. 2004
= 0.89 +/- 0.05M1 = (4.74 +/- 0.50) x 1013 MO
Mmin = 6.10 x 1012 MO
GOODS: Great Observatories Origins Deep Survey
Halos and Galaxies at z~3-5
Lee et al. 2005
Halo substructure:we observe an excess of faintgalaxies around bright ones.massive halos contain morethan one LBG
“Bright Centers”: z_850<24.0“Faint centers”: 24.0< z_850 <24.7“Satellites”: z_850 >25.0
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 range5x1010 – 1012 MO
1-σ scatter between mass and SFRsmaller that 100%
Giavalisco & Dickinson 2001Porciani & Giavalisco 2002Lee et al. 2004, in prep.
GOODS: Great Observatories Origins Deep Survey
EROs, orUV-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 quantifiedand 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 about50% of the volume density of LBGs (highly uncertaint). However; they possibly contribute about up to 100% of the LBG stellar mass density, becausethey have higher M/L ratios Van Dokkum et al. 2004
GOODS: Great Observatories Origins Deep Survey
EROs
Ks< 22, R-Ks>3.35
Moustakas et al. 2004
GOODS: Great Observatories Origins Deep Survey
EROs
•ACS resolution is crucial tounderstand 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
HUDF/GOODS EROs
Yan et al. 2004
GOODS: Great Observatories Origins Deep Survey
HUDF/GOODS EROs
Yan et al. 2004
Uses HUDF plus GOODS-SST data
SED fitting disfavour very dustobscured, 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)
GOODS: Great Observatories Origins Deep Survey
LBGs at z~5 and 6
Yan et al. 2005
Evidence of large stellar mass at z~5, 6
GOODS: Great Observatories Origins Deep Survey
LBGs at z~5 and 6
Yan et al. 2005
Evidence of large stellar massat z~5, 6
GOODS: Great Observatories Origins Deep Survey
An evolved, massive galaxy at z~7?
Mobasher et al. 2005, submitted to Nature
HUDF + GOODS-SST
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
Different populations?
Adelberger et al. 2004
Near-IR selectionpicks up the high-endof the distribution of masses (total and stellar)
GOODS: Great Observatories Origins Deep Survey
Galaxies at z~1-0
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 dominatedstellar mass density; the oppositeat z~0: morphology transformation
Bundy, Ellis & Conselice 2005
Cosmic variance
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 GOODSRavindranath et al. 2003
Tendency for smaller sizes at z~1 (30% smaller)
Number-densities are
relatively constant to z~1
GOODS: Great Observatories Origins Deep Survey
The evolutionary link?
Giavalisco, 2002 ARA&A
The expected evolution of clustering (correlation length) suggests what thehigh redshift galaxies might evolve into at later epochs.
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