Large-Scale Structure at z=1:
Results from the DEEP2 Survey
Alison Coil
Steward Observatory
University of Arizona
March 2006
Talk Overview
•DEEP2 Redshift Survey overview
•Luminosity-dependence of Clustering at z=1
•Galaxy Properties vs. Environment
•Evolution of Blue Fraction in Groups
•QSO-galaxy clustering
The DEEP2 Collaboration
The DEEP2 Galaxy Redshift Survey, which uses the DEIMOS
spectrograph on the Keck II telescope, is studying both galaxy
properties and large-scale structure at z=1.
U.C. Berkeley
U.C. Santa Cruz
LBNL
M. Davis (PI)
S. Faber (Co-PI)
D. Koo
P. Guhathakurta
D. Phillips
K. Noeske
A. Metevier
L. Lin
N. Konidaris
G. Graves
J. Newman
M. Cooper
B. Gerke
R. Yan
C. Conroy
Steward Obs.
A. Coil
C. Willmer
Maryland
B. Weiner
Virginia
R. Schiavon
NOAO
J. Lotz
Comparison with Other Surveys
DEEP2 was designed to have comparable size and density to
previous generation local redshift surveys and is
>50 times larger than previous intermediate surveys at z~0.3-1.
1.00E+06
DEEP2 has a different
geometry than local
surveys: 20x~80x1000
h-3 Mpc3 per field
Number of Galaxies
SDSS
2dF
1.00E+05
LCRS
DEEP2
1.00E+04
1.00E+03
1.00E+05
CFA+
SSRS
z~0
z~1
PSCZ
1.00E+06
1.00E+07
Volume (h -3 Mpc3)
few x smaller than 2dF
>4x larger than VVDS
~2.5x COMBO-17
1.00E+08
Vital Statistics of DEEP2
•3
sq. degrees of sky
• 4 fields (0.5o x <2o) - lower cosmic variance errors
• primary z~0.7-1.4
(pre-selected using BRI photometry)
• >40,000 redshifts
• comoving volume: ~5·106 h-3 Mpc3
• 400 slitmasks over 80 Keck nights
• One-hour exposures
• RAB=24.1 limiting magnitude
• 1200 l/mm: ~6500-9200 Å
• 1.0” slit: FWHM 68 km/s - high-resolution
AEGIS: the All-wavelength Extended
Groth Strip International Survey
Spitzer MIPS, IRAC
DEEP2 spectra
and Ks imaging
HST/ACS
V,I (Cycle 13)
DEEP2/CFHT
B,R,I
GALEX NUV+FUV
Chandra & XMM:
Past coverage
Awarded (1.4Ms)
VLA - 6cm (0.5 mJy) +
21cm (0.1 mJy)
SCUBA
Background: 2 x 2 deg
from POSS
AEGIS ApJ Letters in prep:
Conselice: Properties of Massive and Red Galaxies
Fang: Chandra observations of DEEP2 groups
Georgakakis: Environments of Chandra sources
Gerke: A binary AGN at z=0.71
Huang: Mid-Infrared Spectroscopy of a very massive LBG at z=2.98
Ivison: Deep radio imaging of EGS
Kirby: SEDs of faint galaxies
Le Floc'h: Hidden star formation associated with a bright X-ray source
Lin: SFR in close pairs
Metevier: Tully-Fisher relation for z>=0.9 galaxies in EGS
Moustakas: Strong gravitational lensing in the EGS
Nandra: Host galaxy colors and masses of X-ray selected AGN
Pierce: AGN host morphologies
Weiner: Extinction and Star Formation Rate Calibrations from Optical
Emission Lines
Evolution of Galaxy Morphology in EGS
Poster by J. Lotz on changes in morphological
distribution of galaxies from z=1.2 to z=0.3
using ~2000 DEEP2 galaxies:
1. buildup of E/S0/Sa since z~1
2. red sequence is mostly disk galaxies at z~1 and
E/S0/Sa by z~0.3
3. merger fraction is less than 10% and constant
with z
4. fraction of irregular galaxies decreases toward
low z
5. most 24mm sources are Sc/d/Irr
Redshift Distribution of Data: z~0.7-1.4
Target galaxies to be at z>0.7
with B-R, R-I colors. The cuts
are very successful! Only miss
3% of high-z objects (blue).
Don’t apply color cut in the
EGS.
Redshifts are precise
(30 km/s) and have high
confidence: OII doublet and Ca
H+K abs. features
Status:
-three-year survey
-currently ~90% complete
-finishing EGS this spring
DEEP2 sees the same color bi-modality as
SDSS, COMBO-17, etc. to z>1
red
blue
bright
faint
two distinct spectral
types as well
Evolution of the Luminosity Function
M* evolves by ~1.3
mags/z - brighter in
past for both red and
blue galaxies!
Number density is
~constant for blue
and lower at z=1 for
red galaxies.
Build-up of galaxies
on the red sequence.
The red population is
not just evolving
passively!
Willmer et al, 2005 + Faber et al. 2005, ApJ
Redshift Maps in 4 Fields: z=0.7-1.3
Cone diagram of 1/12 of the full DEEP2 sample
Luminosity-dependence of clustering
at z=1 in DEEP2 data
From a sample of 25,000
redshifts over 3 deg2 in 4 fields create volume-limited
subsamples as a function of
luminosity.
Galaxy separation
(Mpc/h)
100 kpc/h
20 Mpc/h
Brighter samples are more
clustered and have steeper
slopes on small scales -preferentially found in groups
at z=1 -- sub-structure.
Coil et al. 2006, ApJ
Deviations from a power-law at z=1
SDSS z=0.1
DEEP2 z=1
Similar deviations from a power-law that are seen at z=0.1.
Generally interpreted as one-halo and two-halo terms.
Coil et al. 2006, ApJ
Measure one-halo and two-halo terms
Data
Mock
Can measure the one-halo and two-halo terms directly with a group
catalog! Compare with mock catalogs that use an HOD model + DM
NFW profile and find a discrepancy on small scales - ?
Coil et al., ApJ 2005
Luminosity/scale-dependence of bias
Have now measured the
scale-dependence and
luminosity-dependence
of galaxy bias at z=1!
Rise in bias on small
scales reflects physics of
galaxy formation and
radial profile of galaxies
in halos.
DEEP2 sample - large-scales:
b =1.26 (0.04) - 1.54 (0.05)
From the observed bias can infer the dark matter halo
masses that host these galaxies: M > 9 1011-3 1012 Mo/h
Theoretical Modelling of x(r)
Conroy, Wechsler and Kravtsov
2006, ApJ predict the luminositydependent x(r) using dark matter
simulations - identify halos and
subhalos, assign L using the
observed LF and the dist. of
(sub)halo masses by matching
number densities: get a simple
relation b/w L-Vmax of halo
-reproduce DEEP2 results quite
well! (incl. rise on small scales)
Diamonds - DEEP2 results
Solid line - theoretical model
Dotted line - dark matter
Implies that luminositydependence of clustering is
driven by mass of (sub)halos
Galaxy Properties and Environment
SDSS
(Blanton et al. 2004)
blue
color
DEEP2
log overdensity
linear overdensity
We can measure the local density - i.e., the
“environment” of any given object - using the distance
to the 3rd nearest neighbor DEEP2 galaxy.
color red
Cooper et al. 2006, ApJ: astro-ph/0603177
red
blue
Environment over the CMD
SDSS, z~0.1
DEEP2, 0.75<z<1.05
redder
brighter
Basic trends from z~0 studies persist at z~1: e.g., the reddest and
brightest galaxies are preferentially found in dense environments.
Cooper et al. 2006, ApJ: astro-ph/0603177
Environment vs. Luminosity
Red galaxies
denser
Blue galaxies
brighter
brighter
However, unlike locally, red and blue galaxies have very
similar trends of environment vs. luminosity at z~1.
Cooper et al. 2006, ApJ: astro-ph/0603177
denser
In other words…
brighter
There exists a population of bright, blue galaxies in dense
regions that is present at z~1 but not today. Presumably, their
star-formation has quenched and are now on the red sequence.
Baby pictures of today’s RS galaxies?
ACS data in the EGS - bright blue galaxies at z~1
Finding groups in DEEP2
We find groups using the locations of galaxies in redshift space - no
selection based on color, magnitude, etc. - just overdensity in the
galaxy distribution.
position
l
Uses of groups include:
1. LSS/cosmology: N(s,z)
constrains w
2. Galaxy formation and
evolution: e.g., the
Butcher-Oemler effect
First DEEP2 Group Catalog
We currently have group catalogs for all 4 fields
Gerke et al. 2005, ApJ
Color/environment trend is driven by
group (not massive cluster) galaxies
log overdensity
Mean &
median
trends
After group
and cluster
galaxies are
removed
blue
red
Cooper et al. 2006, ApJ: astro-ph/0603177
Do these trends evolve over time?
Sample definition is
critical for a clean test of
the Butcher-Oemler
effect. Volume-limited
samples, to diff. limiting
mag, w/ and w/o passive
evolution. Tested
extensively in mock
catalogs w/ and w/o
evolution in them.
brighter
Gerke et al. 2006, in prep
Evolution of blue fraction in groups
increasing z
The blue fraction is
lower in groups than
the field, but evolves
more quickly, and
appears to be
converging w/ field at
z~1.2.
Suggests that galaxies
in groups start
quenching at z~1.5 or
so.
Gerke et al. 2006, in prep
SDSS QSOs in DEEP2 fields
36 SDSS + 16 DEEP2 spectroscopic QSOs in
the DEEP2 fields between z=0.7-1.4:
Coil et al., ApJ submitted
Clustering of Galaxies around QSOs
Clustering of DEEP2
galaxies around SDSS
QSOs at z=0.7-1.4.
Errors include Poisson
errors + cosmic variance.
Why measure the crosscorrelation? Divide by the
clustering of DEEP2
galaxies around DEEP2
galaxies to get the bias of
QSO hosts…
Coil et al., ApJ submitted
Relative bias of QSOs to DEEP2 galaxies
The relative bias is ~1 +/-0.2
Galaxies that host QSOs at z=1
have the same clustering properties
(same halo mass) as typical DEEP2
galaxies.
Don’t have same clustering as
red/early-type galaxies (2s result) -- see the same result using local
environment/overdensity
Places constraints on theoretical
and semi-analytic models of
quasars (Hopkins, Croton, etc.)
Coil et al., ApJ submitted
Other DEEP2 Papers
•Clustering of Groups and Group Galaxies (Coil et al., ApJ)
•Void Probability Function (Conroy et al., ApJ)
•Merger rate (Lin et al., ApJ)
•Satellite Galaxy Kinematics (Conroy et al., ApJ)
•Environments in Deep Redshift Surveys (Cooper et al., ApJ)
•Metallicities of DEEP2 Galaxies (Shapley et al., ApJ)
•Evolution of Galaxy Morphologies (Lotz et al., submitted ApJ)
•Ages/Zs of early-type galaxies (Schiavon et al., submitted ApJ)
•K+A/post-starburst galaxies (Yan et al., in prep)
•Evolution of fine structure constant (Newman et al., in prep)
Data Release 1 (DR1): http://deep.berkeley.edu/DR1 - 1st season’s
data - 7,500 redshifts + spectra - ~20% of full dataset