Galaxy Clustering Properties at z=1: Results from the DEEP2

Redshift Survey

Alison CoilSteward Observatory

April 2006

Talk Overview

•DEEP2 Redshift Survey overview•Luminosity-dependence of clustering at z=1•QSO-galaxy clustering

The DEEP2 Collaboration

U.C. BerkeleyM. Davis (PI) M. Davis (PI)

M. Cooper M. Cooper

B. Gerke B. Gerke

R. Yan R. Yan

C. ConroyC. Conroy

Steward Obs. A. Coil

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

D. Koo

P. Guhathakurta

D. Phillips

K. Noeske

A. Metevier

L. Lin

N. Konidaris

G. Graves

LBNL J. NewmanJ. Newman

Maryland B. Weiner

Virginia R. Schiavon

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.

C. Willmer

Large-Scale Structure in 2dF

220,000 galaxies in 1500 sq. degrees - z=0.1

Comparison with Other 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 Mpc 3)

Number of Galaxies z~0z~1

DEEP2

SDSS

2dF

CFA+SSRS

LCRS

PSCZ

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.

DEEP2 has a different geometry than local

surveys: 20x~80x1000 h-3 Mpc3 per field

few x smaller than 2dF~4x larger than 1st

epoch VVDS~2.5x COMBO-17

1.5 x COSMOS

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

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….

Redshift Distribution of Data: z~0.7-1.4

Status: -three-year survey-currently ~90% complete-hoping to finish EGS this spring…

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). We do not apply z cuts in the EGS!Redshifts are precise (30 km/s) and have high confidence: OII doublet and Ca H+K abs. features

Observing conditions in spring ‘04 were poor…

The CFHT dome as seen from Gemini

Redshift Maps in 4 Fields: z=0.7-1.3

Cone diagram of 1/12 of the full DEEP2 sample

Galaxy Clustering Primer

(r) follows a ~power-law prescription locally:

(r) = (r0/r) with r0~5 Mpc/h and ~1.8

r0 = scale where the prob. of finding a galaxy pair is 2x random

Smallest scales (r < 100 kpc/h): mergers + galaxy-galaxy interactionsIntermediate scales (100 kpc/h < r < 2 Mpc/h): radial profiles of

galaxies w/in groups and clusters Large scales (r > 2 Mpc/h): large-scale density field / cosmology

Locally, both 2dF and SDSS quantify galaxy clustering to few %-can now measure to similar accuracy at z=1

Luminosity-dependence of clusteringat 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.

Brighter samples are more clustered (r0~3.7-4.4 Mpc/h) and have steeper slopes on

small scales -- preferentially found in groups at z=1 -- sub-

structure.

Coil et al. ApJ, astro-ph/0512233100 kpc/h 20 Mpc/h

Galaxy separation(Mpc/h)

wp(

r p) -

clu

ster

ing

ampl

itud

e

Deviations from a power-law at 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

SDSS z=0.1 DEEP2 z=1

Measure one-halo and two-halo terms

Coil et al., 2005 ApJ

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 - ?

Data Mock

Bias: galaxy clustering/dark matter clustering

Observations + theory: z=3: b~4 z=0: b~1

Galaxy formation sim. at z=3 by Kauffmann et al. grey=dark matter particles colors=galaxies

Bias is expected to evolve with redshift, as first galaxies at high-z

formed in densest regions.

LBGs SDSS

Evolution of bias and dependence on scale and galaxy

properties places strong constraints on galaxy formation

theories.

Luminosity/scale-dependence of bias

From the observed bias can infer the dark matter halo masses that host these galaxies: M > 9 1011-3 1012 M/h

Have now measured the scale-dependence and

luminosity-dependence of galaxy bias at z=1 (assuming CDM).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)

Theoretical Modelling of (r)

Risa will talk about predicting the luminosity-dependent (r) using dark matter simulations and

assigning luminosities to halos:Conroy, Wechsler, Kravtsov astro-ph/0512234

Good agreement with our data implies that luminosity-dependence of clustering is driven by

mass of (sub)halos.

Zheng will talk about performing direct HOD fits to these results, measuring relation between galaxy

luminosity and halo mass and determining the halo mass distributions for central vs. satellite galaxies. We

are comparing with SDSS - measure evolution in HOD.

SDSS QSOs in DEEP2 fields

Coil et al., ApJ submitted

36 SDSS + 16 DEEP2 spectroscopic QSOs in the DEEP2 fields between z=0.7-1.4:

Work done w/ Joe Hennawi + Jeff

Newman

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 cross-correlation? 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 (2 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

Summary

Have measured the luminosity-dependence of galaxy clustering at z=1 in the DEEP2 data. The clustering amplitude is lower than z=0.1 and can be explained as mass-dependent using a simple model to relate luminosity to dark matter halo mass.

See deviations from a power-law on small scales at z=1 for bright galaxies - due to sub-structure.

Directly measure the one-halo and two-halo components of (r) for galaxies in groups.

Can now model the HOD at z=1 and compare with z=0.1 to measure evolution.

Galaxies that host QSOs at z=1 reside in the same mass halos as typical DEEP2 galaxies.