Galaxy Formation and Evolution in Clusters

1
Galaxy Formation and Evolution (in Clusters) 3

• Alice Shapley (Princeton)
• June 14, 15, 16th, 2006

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Overview and Motivation

• 0. Introductory remarks about galaxy
  formation evolution and why clusters are useful
  for this
• Galaxy evolution in clusters from z0-1
  (emphasis on early-type)
• Galaxy evolution in general from z0-1
• Direct observations of cluster galaxy
  progenitors forming at high redshift (z 2)
• Protoclusters at high redshift (z 2)

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III. The Progenitors of Cluster Galaxies Forming
at z2
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Progenitors of Massive Galaxies

• Common theme in earlier lectures the stars in
  E/S0 galaxies formed at high redshift (zgt2)
• Until the mid-1990s the only zgt2 objects known
  were QSOs, radio galaxies, and QS0 absorbers
  (DLA/LLS)
• How can we go about isolating more normal
  galaxies during the epoch of star/galaxy
  formation?
• The study of high-redshift (lets say zgt1.5)
  galaxies has exploded in the last 10 years, with
  multiple techniques for isolating high redshift
  galaxies, making use of multi-wavelength data
  spanning from the radio to the X-ray
• As opposed to traditional magnitude-limited
  surveys, down to specific flux limit, new results
  utilize several complementary selection
  techniques for finding high-z galaxies, selecting
  overlapping yet complementary populations --gt
  must determine how they overlap/complement each
  other to describe entire galaxy population at a
  given epoch.

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Progenitors of Massive Galaxies

• Review of techniques (focus on UV and submm
  selection)
• Some key questions and results

6
Photometric Pre-selection UV

• 50 objects/square arcmin down to R25. How do
  you pick out the high-redshift galaxies?
• Lyman discontinuity at rest-frame 912 A gives
  z3 galaxies very distinctive observed UGR colors

(Steidel et al. 1992, 1993, 1995, 1996, 2003)
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zgt1.5 Rest-UV Color Selection

• z3 UGR Lyman Break criteria, adjusted for z2
  (Adelberger et al. 2004)
• Spectroscopic follow-up with optimized
  UV-sensitive setup (Keck I/LRIS-B)
• 1000 galaxies at z3, gt750 galaxies with
  spectroscopic redshifts at z1.4-2.5, in what was
  previously called the Redshift Desert

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Measuring Redshifts z3

• High redshift
• Lya em/abs, IS abs at zgt2.5
• At z 1.4-2.5, these features are in the near
  UV, while strong rest-frame optical emission
  lines have shifted into the near-IR formerly
  called THE REDSHIFT DESERT

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Redshift Desert

• Low redshift
• Emission-line z
• OII, OIII, Hb, Ha
• At z gt 1.4, OII moves past 9000 AA,
  while Lya below 4000 AA at zlt2.3 no strong
  features in the optical

SDSS galaxy at z0.09
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Redshift Desert

• Low redshift
• Abs-line z
• 4000 AA break, Ca HK, Mg
• At z gt 1.4, 4000AA break moves past 9000 AA

SDSS galaxy at z0.38
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Keck/LRIS-B Efficiency

• LRIS-B 400/3400 grism --gt 40 efficiency from
  3800-5000 AA
• Low night-sky background in near-UV (3 mag
  fainter than at 9000 AA)
• (Steidel et al. 2004)

Unsmoothed
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Measuring Redshifts z2

• Low- and high-ionization outflow lines, Ly?
• He II emission, CIII emission
• Fewer galaxies have Lya emission (57 have no
  Lya) than in z3 sample (cf. SMG!)
• (Steidel et al. 2004)

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Measuring Redshifts z2

• Low- and high-ionization outflow lines, Ly?
• He II emission, CIII emission
• Fewer galaxies have Lya emission (57 have no
  Lya) than in z3 sample (cf. SMG!)
• (Steidel et al. 2004)

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Outflow Kinematics z3 vs. z2

• Kinematic evidence for large-scale outflows is a
  generic feature of UV-selected galaxies at zgt2
• v0 from rest-frame optical nebular emission
  lines OIII at z3 and Ha at z2
• Signature of feedback, perhaps fundamental to
  understanding galaxy formation
• (Steidel et al. 2004)

z3
z2
Unsmoothed
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zgt1.5 Rest-UV Color Selection

• z3 UGR criteria (Lyman Break), adjusted for
  z2 (Adelberger et al. 2004)
• Spectroscopic follow-up with optimized
  UV-sensitive setup (Keck I/LRIS-B)
• 1000 galaxies at z3, gt750 galaxies with
  spectroscopic redshifts at z1.4-2.5, in what was
  previously called the Redshift Desert

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Clustering DM Halo Masses

• 28,500 galaxies
• 21 fields, 0.8 degree2
• 1600 spectroscopic redshifts
• RAB23.5-25.5
• Correlation lengths
  ?z?2.9 (LBG), r04.0?0.6 h-1 Mpc
• ?z?2.2 (BX), r04.2?0.5 h-1 Mpc ?z?1.7
  (BM), r04.5?0.6 h-1 Mpc
• Implied halo masses 1011.5 M?
  (LBG)
• 1012M? (BX/BM)
• (from comparison with GIF-LCDM numerical
  simulation, DM Halos with same clustering)

(Adelberger et al. 2004, based on w(q))
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Evolution of Clustering to z1, 0

• Follow evolution of DM halo clustering in
  simulation
• Matches early-type absorption line DEEP2
  galaxies at z1 (Coil et al. 2003)
• Matches SDSS ellipticals at z0.2 (Budavari et
  al. 2003)
• Typical UV-selected galaxy at z2-3 will
  evolve into an elliptical by z0

(Adelberger et al. 2004)
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zgt1.5 Rest-UV Color Selection

• Large set of results about UV-selected galaxies
  at z1.5-3 abundance and clustering, luminosity
  function, sfr (typical sfr50-100M?/yr), dust
  extinction, metallicities (emission-line,
  absorption-line), detailed spectral properties,
  stellar masses/populations (typical stellar mass
  few x 1010M?, large range), impact on the IGM
  (SNe feedback, ionizing radiation)
• What does UV-selection mean in terms of physical
  properties? Star-formation thats only moderately
  (factor of few-100) extinguished by dust, but a
  large range of stellar masses (smaller range of
  baryonic masses), clustering implies that these
  will correspond to early-type galaxies at z0.

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zgt1.5 Near-IR selection (40 zs)

• Extension of K20 survey group (i.e., get zs for
  everything with Klt20), use B-z, z-K color
  criteria to select both star-forming galaxies and
  passive galaxies at zgt1.4
• Incomplete for fainter objects with small Balmer
  Breaks, weighted more towards fairly massive
  objects
• Significant overlap of BzK/SF with UV-selected
  samples

(Daddi et al. 2004)
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zgt1.5 FIRES/J-K selection (20 zs)
(Franx et al. 2003)
(Reddy et al. 2005)

• J-Kgt2.3 criteria meant to select massive evolved
  galaxies with significant Balmer/4000 Å breaks at
  zgt2 turns out selection also yields massive
  dusty starbursts
• 25 appear to contain AGN (much higher than
  fraction of UV-selected population)
• Only limited number of spectroscopic redshifts

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zgt1.5 Submm Selection (75 zs)
(courtesy I. Smail)
(Smail 2005)

• Submm galaxies, dusty, most of luminosity comes
  out in submm waveband
• First detected by SCUBA/JCMT in 1997 at 850 ?m
• Counts 1000/sq. degree at 5 mJy (limit of
  bright SCUBA survey) a few hundred submm
  galaxies IDd
• In principle, SCUBA is sensitive to dusty
  galaxies out to z6 (negative K-correction)

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zgt1.5 Submm Selection (75 zs)
(courtesy I. Smail)
(Chapman et al. 2005)

• Breakthrough using radio (1.4 GHz) positions
  for optical spectroscopy (ameliorates ambiguity
  from 15 SCUBA beam), 70 of sources
• Redshifts enable study of physical properties
• Typical LIR8x1012L? and dust temperature Td38K
  (confirmed by 350 ?m observations)
• Less than 10 of submm galaxies are at zgtgt3

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zgt1.5 Submm Selection (75 zs)
(courtesy I. Smail)
(Chapman et al. 2005)

• IR luminosities correspond to sfr gt1000 M?/yr
  (Salpeter) if bulk of FIR is powered by star
  formation. If SF lasts for 108 yr, significant
  stellar mass formed
• Much rarer than other samples, but higher
  inferred SFR, could contribute significantly to
  sfr density at high z

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zgt1.5 Submm Selection (75 zs)
(Chapman et al. 2003)

• Rest-frame UV spectra obtained with Keck/LRIS-B
  (like UV-selected samples)
• Spectra show features of star-formation and AGN
  (Ly?, NV, CIV, SIV), rest-frame optical spectra
  sometimes NII/H?????or broad H?
• Raises question of AGN contribution to
  bolometric luminosity, Deep (Chandra 2 Msec
  image) X-ray emission indicates presence of Fe
  K??line, and absorbed non-thermal continuum slope
• BUT AGN appears not to be energetically
  important -gt submm emission dominated by star
  formation

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zgt1.5 Submm Selection (75 zs)
Note galaxies w/ smaller star formation rates
not detected yet in CO
(Tacconi et al. 2006)

• Masses stellar masses estimated from
  SED-fitting (how does AGN affect stellar mass
  estimates?) dynamical masses estimated from H?,
  CO-linewidths cold molecular gas masses
  estimated from CO line luminosities
• Dynamical masses w/in 10kpc, 2x1011 M?(Swinbank
  et al. 2004, 2006), molecular gas masses 5x1010
  M? (Tacconi et al. 2006)

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zgt1.5 Submm Selection (75 zs)

• Submm galaxies appear to be massive systems with
  prodigious star-formation rates, may also be
  strongly clustered (but uncertain because of
  small number of redshifts)
• Could be progenitors of QSOs, massive galaxies
  at lower redshift
• More robust mass estimates (disks, mergers?),
  and estimate of AGN contamination to bolometric
  luminosity
• Interesting note several years ago, a lot was
  made of the fact that there was so little overlap
  between submm galaxies and z3 LBGs. But now we
  know that most submm galaxies are at zlt3, and
  have similar redshift distribution to z2
  UV-selected galaxies. 65 of submm galaxies have
  colors of UV-selected galaxies (but bigger
  star-formation rates)

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zgt1.5 Summary

• In addition to UV-selected, BzK, J-K, submm,
  there are other techniques, such as the
  K-band/photo-z technique of the Gemini Deep Deep
  Survey (GDDS), and new Spitzer capabilities IRAC
  (mass-selected), MIPS/24 micron (sfr-selected,
  analogous to SCUBA)
• Now that there are several groups using
  different selection techniques to find galaxies
  at z2, we need to understand how the samples
  relate to each other (each sample has certain
  benefits but is incomplete e.g., UV-selected
  sample has largest set of redshifts and spectra)
• Reddy et al. (2005) considered the overlap among
  different samples, and contribution of each to
  the sfr density at z2-2.5

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Key Questions

• What is the evolution in global sfr and stellar
  mass density vs. z?
• What is the evolution in number density of
  galaxies as a function of (stellar) mass and
  star-formation rate?
• What are the star-formation histories of
  galaxies (burst/episodic, continuous), and how do
  they accumulate their stellar mass?
• What are the origins of different morphological
  types?
• What is the chemical enrichment in galaxies vs.
  z, and by how much do they enrich their
  surroundings (vs. mass)?
• What is the effect of supernovae/AGN feedback on
  gas in galaxies and the surrounding IGM?
• How do we make a continuous timeline of galaxies
  from high redshift to z0 (map one sample to
  another)?

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Key Techniques/Goals

• New multi-wavelength technologies are helping us
  address these questions, beyond ground-based
  optical imaging and spectroscopy
• Wide-field near-IR imaging (stellar masses) and
  near-IR spectroscopy (dynamical masses, sfr,
  chemical abundances)
• Chandra X-ray observations (sfr and AGN)
• Spitzer/IRAC (stellar masses) and MIPS (dust
  luminosity, sfr)
• HST ACS/NICMOS (morphologies)
• Full understanding of energetics and stellar and
  metal content is a multi-wavelength endeavor
• Detailed comparison with numerical simulations
  and semi-analytic models

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Morphological Classification?

• 240 UV-selected galaxies with spectroscopic zgt1.4
• Do not exhibit regular morphologies!!

BX/BM/LBG with Rlt25.5
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50 GOODS-N Galaxies, z1.5-2.0
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Morphological Classification? Sizes

• Half-light radii of GOODS/ACS (HST) galaxies
  measured as a function of radius
• Compared with models of dark matter halos of
  fixed mass (green) or fixed virial velocity (red)

(Ferguson et al. 2004)
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IV. Protoclusters at High Redshift (z2)
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Finding High-z Protoclusters

• Highest redshift X-ray-detected cluster at
  z1.45 (Stanford et al. 2006)
• But there are large-scale overdensities of
  galaxies that have been detected at z2, which
  may evolve into gt1014M?clusters by z0
• Significant galaxy overdensities serendipitously
  discovered during UV-selected survey (z3.09,
  2.30, 2.85)
• Overdensities of Ly? emitters discovered around
  targeted radio galaxies at 2ltzlt5

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Q170064 Field

• QSO field (V16, zem2.72), very sensitive obs.
  of IGM
• Optical, near-IR imaging and spectra
• Spitzer/IRAC photometry 3.6-8.0 mm (Barmby et
  al. 2004)
• 72 gals at z1.4-2.9 (most are at zlt2.5) with
  optical-IRAC SEDs and redshift IDs--gt stellar
  populations, masses (Shapley et al. 2005)
• BC2003 exp(-t/t) and CSF models, Calzetti
  extinction
• Serendipity Large redshift spike at
  z2.299/-0.015 (20 galaxies) --gt study
  properties vs. environment

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Stellar Populations Masses

• Near/Mid-IR Imaging
• Deep J, K imaging with WIRC, Palomar 5-m, to
  Ks22.5, J23.8
• Spitzer IRAC data at 3.6, 4.5, 5.4, 8 ?m
• Use for modeling stellar populations, masses

Ks (2.15 mm)
(Barmby et al. 2004, Steidel et al. 2005)
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Stellar Populations Masses

• Near/Mid-IR Imaging
• Deep J, K imaging with WIRC, Palomar 5-m, to
  Ks22.5, J23.8
• Spitzer IRAC data at 3.6, 4.5, 5.4, 8 ?m
• Use for modeling stellar populations, masses

IRAC (4.5 mm)
(Barmby et al. 2004, Steidel et al. 2005)
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Q170064 The z2.3 Spike

• Only identified 25 of galaxies in the field -gt
  gt80 galaxies in the spike
• Galaxy redshift overdensity, dgal7,
  real-space matter overdensity ?m1.8, will
  virialize by z0 with M1015M?
• ltMstargt in spike is x2 larger than outside
• ltAgegt in spike is 1.4 Gyr, whereas it is 0.7 Gyr
  outside
• zform earlier in spike?
• Now with HST were looking at morphology vs.
  environment (hard!!)

(Steidel et al. 2005)
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Finding High-z Protoclusters UV

• At least 2 other examples of galaxy spikes
  discovered in UV surveys by Steidel et al.
• 1) z3.09 (first evidence that LBGs were strongly
  clustered)

2) z2.85 at the same redshift as bright QSO
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Finding High-z Protoclusters HiZRG

• Environments of high-redshift radio galaxies
  make useful protocluster targets
• -gtHiZRG may have extreme stellar masses
  (1012M?), based on K-band magnitudes
• -gt extended clumpy morphology consistent w/
  simulations of formation of brightest cluster
  galaxies
• -gtstrong clustering at z1
• -gtextreme radio rotation measures, indicative
  of dense hot gas environments large Ly? halos,
  regions consistent w/ originating from a cooling
  flow

From Pentericci et al. (1998), clumps spread over
100 kpc in z2.16 HiZRG
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Finding High-z Protoclusters HiZRG

• VLT program to target 10 HiZRG at 2ltzlt5,
  searching for overdensities in galaxies (Miley,
  Rottgering, de Breuck, Kurk, Overzier)
• Use Ly??NB imaging to measure the of Ly?
  emitters at redshift of radio galaxy and estimate
  overdensity (design special filter that is Ly? at
  the redshift of the AGN)
• In some cases, have followed up with H?, and
  surveyed fields for LBGs

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Finding High-z Protoclusters HiZRG

• HiZRG 1138-262, z2.16, K16, stellar
  mass1012M?
• ( Left) HST/WFPC2/F606W image of HiZRG
• (Right) Lya emission spectra for 14 confirmed
  galaxies at redshift of AGN

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Finding High-z Protoclusters HiZRG

• HiZRG 1138-262, z2.16, K16, stellar
  mass1012M?
• (Right) Histogram of 15 emitters, solid curve is
  response of NB filter, use histogram of Ly?
  velocities to get dynamical mass, gt 1014 M?, more
  difficult to quantify than for LBGs

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Finding High-z Protoclusters HiZRG

• Several more targets at zgt2
• Implications protocluster masses1014-1015M?
• Look at galaxy properties as a function of
  environment

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Concluding Philosophical Comment

• Rich set of observations of galaxies in the
  early universe, for statistical samples of
  galaxies selected with different techniques
  (though its still a challenge to get spectra)
• Much much more that I could have presented
• Field of zgt1.5 galaxy evolution is completely
  different since just 10 years ago, when
  UV-selection technique was first implemented
• Whats happening in the next 10 years?
  (feedback, connecting to samples at other
  redshift, building mass/sfr-limited samples, disk
  galaxies)