Galaxy Clustering Properties at z=1: Results from the DEEP2 Redshift Survey Alison Coil Steward Observatory April 2006

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

The DEEP2 Collaboration U.C. Berkeley M. Davis (PI) M. Cooper B. Gerke R. Yan C. 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. 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 z~0 z~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~ DEEP2 has a different geometry than local surveys: 20x~80x1000 h -3 Mpc 3 per field few x smaller than 2dF ~4x larger than 1st epoch VVDS ~2.5x COMBO x COSMOS

Vital Statistics of DEEP2 3 sq. degrees of sky 4 fields (0.5 o x <2 o ) - lower cosmic variance errors primary z~ (pre-selected using BRI photometry) >40,000 redshifts comoving volume: ~5·10 6 h -3 Mpc slitmasks over 80 Keck nights One-hour exposures R AB =24.1 limiting magnitude 1200 l/mm: ~ Å 1.0” slit: FWHM  68 km/s - high-resolution

Coordinated observations of the Extended Groth Strip (EGS) Spitzer MIPS, IRAC DEEP2 spectra and Caltech / JPL K s imaging HST/ACS V,I (Cycle 13) Background: 2 x 2 deg from POSS DEEP2/CFHT B,R,I GALEX NUV+FUV Chandra & XMM: Past coverage Awarded (1.4Ms) Plus VLA (6 & 21 cm), SCUBA, etc….

Redshift Distribution of Data: z~ 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= Cone diagram of 1/12 of the full DEEP2 sample

Galaxy Clustering Primer  (r) follows a ~power-law prescription locally:  (r) = (r 0 /r)  with r 0 ~5 Mpc/h and  ~1.8 r 0 = scale where the prob. of finding a galaxy pair is 2x random Smallest scales (r < 100 kpc/h): mergers + galaxy-galaxy interactions Intermediate 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 clustering at z=1 in DEEP2 data From a sample of 25,000 redshifts over 3 deg 2 in 4 fields - create volume-limited subsamples as a function of luminosity. Brighter samples are more clustered (r 0 ~ Mpc/h) and have steeper slopes on small scales -- preferentially found in groups at z=1 -- sub- structure. Coil et al. ApJ, astro-ph/ kpc/h20 Mpc/h Galaxy separation (Mpc/h) w p (r p ) - clustering amplitude

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=0.1DEEP2 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 - ? DataMock

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 > 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) (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/ 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= : Work done w/ Joe Hennawi + Jeff Newman

Clustering of Galaxies around QSOs Clustering of DEEP2 galaxies around SDSS QSOs at z= 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.