UCSC - August, 2004

Large-Scale Structure in the DEEP2 Galaxy Redshift Survey

Jeffrey NewmanLawrence Berkeley National Laboratory

And The DEEP2 Team

Large-Scale Structure of the DEEP2 team

U.C. BerkeleyM. Davis (PI)

A. Coil

M. Cooper

B. Gerke

R. Yan

C. Conroy

LBNL J. Newman

U. Hawaii N. Kaiser

U.C. Santa Cruz S. Faber (Co-PI)

D. Koo P. Guhathakurta

D. Phillips C. Willmer B. Weiner

R. Schiavon K. Noeske A. Metevier

L. Lin N. Konidaris

G. Graves

JPL P. Eisenhardt

Princeton D. Finkbeiner

U. Pitt. A. Connolly

K survey (Caltech) K. Bundy

C. Conselice R. Ellis

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.

UCSC - August, 2004CDM Universe

LSS provides the link between galaxies and their cosmological context

LSS

Nearly Normal(?) Galaxies

UCSC - August, 2004

Outline

I. The DEEP2 Redshift Survey

II. Clustering of Galaxies in DEEP2

III. DEEP2 galaxies and their environments

IV. Galaxy groups in DEEP2

V. Voids in DEEP2

UCSC - August, 2004

Scientific Goals of the DEEP2 Galaxy Redshift Survey

1. Characterize the properties of galaxies (colors, sizes, linewidths, luminosities, etc.) at z~1 for comparison to z~0

2. Study the clustering statistics (2- and 3-pt. correlations) of galaxies as a function of their properties, illuminating the nature of the galaxy bias

3. Determine N(z) of groups and clusters at high redshift, providing constraints on m and w

4. Measure the small-scale “thermal” motions of galaxies at z~1, providing a measure of the mass of the halos the galaxies are within

UCSC - August, 2004

Comparison with Local Surveys

1.00E+03

1.00E+04

1.00E+05

1.00E+06

1.00E+05 1.00E+06 1.00E+07 1.00E+08

Volume ( h -3 Mpc3)

Number of Galaxies z~0z~1

DEEP2

SDSS

2dF

CFA+SSRS

LCRS

PSCZ

DEEP2 was designed to have comparable size and density to the previous generation local redshift surveys and is

>50 times larger than past surveys at z~0.3-1.

DEEP2 is similar to LCRS in sample

size, but at z~1

UCSC - August, 2004

DEEP2 has been made possible by DEIMOS, a new instrument on Keck II

DEIMOS (PI: Faber) and Keck provide a unique combination of wide-field multiplexing (up to 160 slitlets over a 16’x4’ field), high resolution (R~5000), spectral range (~2600 Å at highest resolution), and telescope size.

UCSC - August, 2004

A Redshift Survey at z~1Observational details:

• 3 sq. degrees over 4 fields• primary z~0.75-1.4 (pre-selected using BRI photometry)• ~5·106 h-3 Mpc3 volume• lookback 6 - 8.5Gyr• >400 1-hour exposures• >40,000 z’s to RAB=24.1 • 1200 l/mm: ~6500-9200 Å• 1.0” slit: FWHM 68 km/s

Color cut used in 3 of 4 DEEP2 fields

UCSC - August, 2004

Redshift Distribution of Data: z~0.7-1.4

Status: - Designed as a

three-year survey- Began summer 2002- 80 night UC time allocation is now complete-Finished 3 of 4 fields, 4th >75% done (will complete in S06)

Our color cuts are very successful! ~90% of our targets are at z>0.75 and we miss only 3% of high-z objects.

UCSC - August, 2004

Coordinated observations ofthe Extended Groth Strip

(EGS)Spitzer MIPS, IRAC

DEEP2 spectra and Caltech / JPL Ks imaging

HST/ACSV,I (Cycle 13)

Background: 2 x 2 degfrom POSS

DEEP2/CFHTB,R,I

GALEX NUV+FUV

Chandra & XMM: Past coverage Awarded (1.4Ms)

Plus VLA (6 & 21 cm), SCUBA, etc….

UCSC - August, 2004

LSS in DEEP2 vs. local surveys

Structure seen in DEEP2 7 Gyr ago looks similar to that in SDSS (rescaling by the cosmic expansion); another sign that we live in a Universe with low m. Detailed studies can test Dark Energy models and galaxy formation scenarios.

UCSC - August, 2004

DEEP2 sees the same color bimodality as SDSS, COMBO-17,

etc. to z~1.4

Our R-band magnitude limit corresponds to ~4000Å rest-frame at z=0.7, ~2800 Å at z=1.4 . As redshift increases, red galaxies of a given luminosity fall out before blue ones. Nevertheless, bimodality appears to persist to the limits of the survey, and is a vital tool for many of our analyses.

Willmer et al. 2005

UCSC - August, 2004

Galaxy Clustering in DEEP2

We are now performing a second generation of studies of the galaxy correlation function using volume-limited samples and a much larger dataset. Locally, (r) is roughly a power-law: (r0/r) with r0~5 Mpc/h and ~1.8. Local trends of correlation vs. color persist at z~1.

Coil et al. 2005, in prep.

(for L>=L*, z=0.7-1.0, preliminary:)

red: r0=5.09 (0.11) =1.95 (0.05) blue: r0=3.56 (0.07) =1.74 (0.05)

UCSC - August, 2004

(rp,) depends strongly on color

Red galaxies not only have a larger correlation length, but alsolarger velocity dispersion/fingers of god: they

reside in more clustered / denser environments. We detect coherent infall on large scales for both blue and red galaxies.Coil et al. 2005, in prep.

UCSC - August, 2004

Clustering vs. Luminosity in DEEP2

We are starting to measure correlation statistics of galaxies as a function of many other properties: luminosity, linewidth/velocity dispersion, stellar mass, morphology, etc. Many comparisons to models will soon be possible.

Coil et al. 2005, in prep.As at low z, brighter galaxies

cluster more strongly in DEEP2.

UCSC - August, 2004

Galaxy Properties and Environment We measure galaxy environments using projected 3rd-nearest

neighbor distance, shown to be near-optimal in Cooper et al. 2005 (accepted). As at z~0, there is a strong trend of galaxy density with restframe color. [OII] trends are weaker and explained by color.

Cooper et al. 2005, in prep.

blue color red

line

ar o

verd

ensi

ty

blue color red

log

over

dens

ityDEEP2SDSS

(Blanton et al. 2004)

UCSC - August, 2004

Environment over the CMD

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. 2005, in prep.

brighter

redder

SDSS, z~0.1 DEEP2, 0.75<z<1.05

UCSC - August, 2004

Environment over the CMD, II

However, unlike locally, red and blue galaxies have very similar trends of environment vs. luminosity at z~1. Suggestive that the bright blue galaxies we see at z~1 will be part of the red population at z~0.

Cooper et al. 2005, in prep.

Blue galaxies Red galaxies

brighter

dens

er

UCSC - August, 2004

Galaxy groups in DEEP2 We can focus on galaxy populations in the densest regions by studying groups of galaxies. We identify groups in DEEP2 by finding overdensities in the galaxy distribution in redshift space using the VDM algorithm of Marinoni et al. (2002).

We are identifying groups in DEEP2 not only to study galaxy evolution, but also because their apparent abundance provides a test of dark energy models. (N.B. For our purposes, “clusters” are just especially massive groups.)

, zposition

Group in early DEEP2 data ~250 km/sec

UCSC - August, 2004

Evolution of blue fraction in groups

We define the blue fraction using galaxies to the left of a limit shown by the dashed line in the CMDs below (to which we are complete at all z), dividing at the dotted line.

Blue fraction is lower in groups than the field, but appears to be converging at z~1.1.

Gerke et al. 2005, in prep. (SEE POSTER!)

UCSC - August, 2004

Group & galaxy correlation functions

Coil et al. 2005, submitted, astro-ph/0507647

We can also use correlation statistics to study the relationship between galaxies and groups. The group-galaxy cross-correlation shows how galaxies are clustered within and around groups. Red galaxies are preferentially found near the centers of DEEP2 groups, while blue galaxies actively avoid them. We’re testing the same thing in many ways…

UCSC - August, 2004

Group-based correlations are sensitive to relationship between galaxies & halos

Coil et al. 2005, submitted, astro-ph/0507647

Mock catalogs which match early DEEP2 (r) predict very different clustering of group galaxies or field galaxies than observed.

UCSC - August, 2004

Void statistics at z~1 and z~0We have studied the Void Probability Function (VPF) - the

probability that a sphere of radius R centered at a random point contains no galaxies - using both DEEP2 and SDSS data.

The VPF can be described by an infinite sum of higher-order correlation functions and potentially contains a wealth of information on biasing, etc. However, a simple “negative binomial” ansatz predicts the observed VPF very well, given only the two-point correlation function and the number density of the tracer used.

Conroy et al. 2005, submitted, astro-ph this week

UCSC - August, 2004

Measuring the VPF

Conroy et al. 2005, submitted

Voids are larger for brighter / redder / less common galaxies.

“Negative binomial” ansatz works fairly well for both

DEEP2 & SDSS data, for all subsamples and scales probed.

DEEP2

SDSS“Negative binomial” model matches VPF for dark matter halo

centers (not mass points) in simulations - insensitive to halo

model parameters.

UCSC - August, 2004

ITo understand the evolution of galaxies, we need to know not just how things change… but where!

DEEP2 is opening many new windows on galaxies by allowing us to study them

within their LSS context over a >7 billion year span. Many more analyses

still to come!

UCSC - August, 2004

Other recent and upcoming papers include:• Angular clustering of galaxies: Coil et al., 2004, ApJ, 617, 765• DEEP2 survey strategy & dark energy: Davis et al.,astro-ph/0408344• Evolution of close-pairs/merger rates: Lin et al., 2004, ApJ, 617, 9• DEEP2 Group catalog: Gerke et al., 2005, ApJ, 625, 6• Satellite galaxy kinematics: Conroy et al., astro-ph/0409305• Environment in deep redshift surveys: Cooper et al., acc. (0506518)• DETF white paper: Davis et al., astro-ph/0507555• Luminosity function: Willmer et al. & Faber et al., submitted• Metallicities of DEEP2 galaxies: Shapley et al., submitted• K+A galaxies in DEEP2 : Yan et al., in prep. (SEE POSTER!)• Test for evolution in fine structure constant: Newman et al., in prep.

First semester’s data is now public: http://deep.berkeley.edu/DR1

UCSC - August, 2004

Color vs. Equivalent Width of [OII]

Red galaxies have low [OII] equivalent width, while blue galaxies span a wide range. It appears that the scatter in this relation is most likely not due to environment. Color correlates better with environment than [OII] EW; there is little residual trend when env. vs. color trend is removed (diamonds).

Why search for groups in DEEP2?In Newman et al. (2002) we showed that the apparent abundance of groups as a function of redshift and velocity dispersion, dN(,z)/dzd, provides a useful test of the dark energy equation of state. For modest-mass groups, this is dominated by differences in the volume element (which varies by 3x between w=0 and w=-1), though affected by the growth factor as well.

Changes to constraint estimatesWe have recently added completely-covariant (i.e. pessimistic) systematic errors to our constraint estimates, and fixed an error in our growth factor calculations noticed by Eric Linder.

Here we plot the new 95% error contours for a CDM model resulting from combining DEEP2 with SDSS results, including systematic errors but assuming 8 is known.

Tests with mocks indicate we can use groups with >350 km/sec reliably.

Constraints for w=-0.7

As for most techniques, constraints are a bit stronger for w=-0.7 models than w=-1.

UCSC - August, 2004

We are beginning to measure w…

N() from 314 groups are plotted. Even ignoring redshift information, the sensitivity to w is clear. However, the group abundance also depends on other parameters we need to tie down…Furthermore, we are still checking systematics!!

Gerke et al. 2005

UCSC - August, 2004

8 Dependence of N()

The normalization of the Power Spectrum, 8, can strongly influence the abundance of groups, as if 8 is greater, fluctuations are larger and groups are more common.

To be able to constrain w, we need an accurate measurement of 8 . New SDSS studies are now making this possible (e.g.. Seljak et al. 2004).

M Dependence of N()

The number of high-redshift groups is sensitive to M .

However, given a value of 8, the z~0 SDSS cluster abundance will tie down M very tightly (Newman et al. 2002).

UCSC - August, 2004

Velocity bias and N()

A final degenerate parameter is the “velocity bias”, bv. This is the factor by which the velocity dispersion of galaxies in a cluster differs from the dark matter dispersion. Some simulations currently favor bv=1.1, others 0.9.

In the end, our results match bv~1.1, M ~0.4, 8~1, or w ~-1.25.

UCSC - August, 2004

Some conclusions• Our results are consistent with no evolution in the fine structure constant from z~0 to z~0.7.

• Large surveys can make possible many kinds of scientific discoveries, and go far beyond whatever topics and fields are thought to be interesting when the survey is designed.

•Future baryonic oscillation surveys may be able to do very well at constraining evolution in , if they have the resolution and right wavelength coverage; they will have large samples of bright, star-forming galaxies at z~1. 100x larger samples may be feasible.

UCSC - August, 2004

Looking for changes from z=0

Start with the simplest thing: combine all data with z>0.6 into one bin, and measure <2>.

UCSC - August, 2004

Results - exploring d/dt

UCSC - August, 2004

Redshift Maps in 4 Fields: z=0.7-1.3

Cone diagram of 1/12 of the full DEEP2 sample

UCSC - August, 2004

Finding groups in DEEP2 We find groups using the locations of galaxies in redshift space - no photometric information is used, just the overdensity in the 3d galaxy

distribution.

position

Group in early DEEP2 data

In particular, we are using the Voronoi-

Delaunay Method of Marinoni et al. (2002),

which has been optimized for use at high z and

performs well. (For our purposes, “clusters” are just especially massive

groups.)

Why search for groups in DEEP2?In Newman et al. (2002) we showed that the apparent abundance of groups as a function of redshift and velocity dispersion, dN(,z)/dzd, provides a useful test of the dark energy equation of state. Here we plot the expected 95% error contours for CDM from combining DEEP2 with SDSS results, including systematics. Tests with mocks indicate we can use groups with >350 km/sec for this.

UCSC - August, 2004

First DEEP2 Group Catalog

Gerke et al. 2005, astro-ph/0410721

We currently have group catalogs for 3 fields

UCSC - August, 2004

Group Richness Distribution

Most groups have N=2-3 within our sample(but we are sampling ~L* galaxies - there are many more fainter galaxies

in these groups)

Ngroups

>200 km/s)

group richness

Gerke et al. 2005, astro-ph/0410721

UCSC - August, 2004

Galaxy properties in groups

We are using the group catalog to study galaxy properties within groups. We find that redder, early-type galaxies are preferentially found in groups at z~1, similar to local trends.

0.7<z<0.9Gerke et al. 2005

UCSC - August, 2004

The Voronoi-Delaunay Method Group-Finder (VDM)

• We use the Voronoi cell volume to find dense regions: potential ‘group seeds’.

• Then we use the Delaunay mesh, its geometric dual, to estimate density of group core.

• Then we search adaptively for group members based on central density estimate.

• We have been testing VDM extensively using realistic DEEP2 mock catalogs to optimize the group-finder and test our systematics.

UCSC - August, 2004

K+A Post-Starburst Galaxies

Yan et al. in prep

K+A galaxies show little on-going star-formation (lack of OII) but strong Balmer features due to recent star-formation (within 1 Gry) -

‘post-starburst galaxies’. These objects are rare, but we cover a large enough volume to find a large statistical sample.

Have ~100 galaxies with features of K stars (old, elliptical-type spectra) and A stars (youngish,

<1 Gyr) - K+A galaxies.

UCSC - August, 2004

K+A Post-Starburst Galaxies

These galaxies populate the ‘gap’ in the color bi-modality and lie on the red sequence - they may provide clues as to how galaxies move onto the red sequence. We are currently estimating

evolution in the rate of K+A galaxies from z=1 to z=0 and investigating their morphologies and

environments.

Yan et al. in prep