Alison Coil UC-Berkeley for the DEEP2 Survey Team August 2004 Galaxy Clustering and Environment Results from the DEEP2 Survey

The DEEP2 Collaboration U.C. Berkeley: M. Davis (PI), A. Coil, M. Cooper, B. Gerke, R. Yan, C. Conroy 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 Hawaii: N. Kaiser LBNL: J. Newman U. Pitt.: A. Connolly JPL: P. Eisenhardt Princeton: D. Finkbeiner

A Redshift Survey at z=1: The DEEP2 Galaxy Redshift Survey, which uses the DEIMOS spectrograph on the Keck II telescope, will study both galaxy properties and the clustering of galaxies at z= sq. degrees 4 fields (0.5 o x 2 o ) primary z~ ~50,000 redshifts ~6·10 6 h -3 Mpc 3 90 Keck nights One-hour exposures R AB =24.1 z~0 z~1 DEEP2 SDSS 2dF CFA+ SSRS Comparison with local samples: LCRS PSCZ

Our color cuts are highly successful! By applying a relatively simple BRI color cut, we have a sample that is 13% z 60% with no cut. Only 3% of objects that we reject are at z>0.75. In the Extended Groth Strip, we apply no color cut, enhancing multiwavelength studies and also making this test possible.

DEEP2 vs. previous surveys of distant galaxies Galaxies found in large numbers well beyond z=1 Obs. R-I Rest U-B Color bimodality note the z=0.7 color cut

Slitmask spectroscopy Using custom-milled slitmasks with DEIMOS we are obtaining spectra of ~120 targets at a time. A total of 480 slitmasks will be required for the survey; we can tilt slits up to 30 degrees to obtain rotation curves.

A fully automated reduction pipeline A few percent of one DEEP2 mask, rectified, flat-fielded, CR cleaned, wavelength-rectified, and sky subtracted. Note the resolved [OII] doublets. Shown is a small group of galaxies with velocity dispersion   250 km/s at z  1. Note the clean residuals of sky lines! SDSS spectral pipeline code by Schlegel et al. allowed us to rapidly develop a full 2d and 1d spectral reduction pipeline that is completely automated. Check z’s by eye.

Status of the DEEP2 Survey DEIMOS commissioning began June 2002 under clear skies and was extremely successful. DEEP2 observing campaign began in July At the end of 3 semesters of the 6 planned, we had completed 48% of the survey slitmasks! We are on schedule! Observations complete mid Currently ~60% done!

Clustering in DEEP2: First Redshift Maps Projected maps of two DEEP2 pointings (of 13 total). Red = early-type (from PCA).

2-point correlation function:  (r) From the projected function w p (r p ) we can recover the real-space correlation function  (r)= (r 0 /r)  z= : r 0 =3.53 +/ z= : r 0 =3.12 +/ both have slope  = / Errors are estimated using mock catalogs - dominated by cosmic variance  (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 probability of finding a galaxy pair is 2x random

Galaxy bias: galaxy/dark matter clustering Bias evolves with redshift: z=3: b~4 z=0: b~1 Galaxy formation simulation by Kauffmann et al. grey=dark matter particles colors=galaxies DEEP2 sample as a whole: b=0.96 +/-0.13 for  8 =1 today b=1.19 +/-0.16 for  8 =0.8 today could be the result of our R-band target selection – we’re under- sampling older, red stellar populations Coil et al astro-ph/

Clustering as a function of Color and Spectral Type Redder galaxies have a larger correlation length and larger velocity dispersion, as do absorption-line galaxies: reside in more clustered / dense environments. Red galaxies: dashed lines Blue galaxies: solid lines

Galaxy Clustering: color, type, luminosity Redder, passively-evolving and/or more luminous galaxies cluster more strongly than bluer, star- forming, less luminous galaxies - similar as z~0 results Color B-R>0.7: r 0 = 4.32 (0.73)  =1.84 (0.07) B-R<0.7: r 0 = 2.81 (0.48)  =1.52 (0.06) Spectral Type Absorption: r 0 = 6.61 (1.12)  =1.48 (0.06) Emission: r 0 = 3.17 (0.54)  =1.68 (0.07) Luminosity Brighter M B <-19.75: r 0 = 3.70 (0.65)  =1.60 (0.06) Fainter M B >-19.75: r 0 = 2.80 (0.48)  =1.54 (0.06)

Projected Angular 2-pt corr. fnct:  Have photometry for many more galaxies than spectra: ~350,000 galaxies over 5 deg 2, incl. z<0.7 Projected angular 2-point correlation function:  Constrain the 3d galaxy clustering  (r) * if the z dist. of the sources is known 7”3’ slope = -0.8: Smooth decrease in clustering with magnitude. Errors are variance across 15 pointings.

Evolution of Galaxy Clustering  (r,z)=  (r,z=0) (1+z) –(3+  )  =-1.2 fixed in comoving coords.  =0 fixed in proper coords.  >0 clustering grows in proper coords. We find no single value of  fits our data –  must evolve with z. We see significant growth in the clustering amplitude from z>1 to 0. Use DEEP2 spectroscopic sample to measure the redshift distribution of sources in various magnitude ranges. Data is from the Groth Strip where we have no photo-z cut – 3320 galaxies. dn/dz=A z 2 e (-z/z0) /z 0 3 Angular correlation function is an integral of the 3-d clustering along the line of sight.

Angular Clustering as fnct. of R-I color redblue In addition to a trend of redder galaxies being more clustered, the bluest galaxies (R-I <0.2) are also highly clustered – unexpected! blue red Redshift distribution of color samples: Reddest galaxies are at z~0.85, narrow Bluer samples are at lower z, wider Bluest samples have significant components at z<0.5 and z~1.7

Clustering as a function of R-I color Reddest galaxies are likely z>0.5 progenitors of local ellipticals Bluest galaxies are a mix of brightest objects at z>1.4, local faint blue dwarfs, and AGN between z~0-2 Corrected for z>1.4 galaxies Coil et al astro-ph/

Galaxy properties and environment Measure galaxy environment using projected Nth-nearest neighbor distance. See strong trends of restframe color and OII equivalent width with environment. No residual trend in OII EW once the correlation of environment with color is removed. Cooper et al. in prep blue color red environment OII equivalent width

Color-magnitude vs environment Redder galaxies reside in denser environments, with the brightest red galaxies in the most dense environments. Within the blue galaxy population, the brightest also lie in the most dense environments - progenitors of central cluster galaxies at z~0? Bright blue galaxies in densest environments Color vs mag. w/ density contours darker regions = more dense

Galaxy Groups and Clusters in DEEP2 Gerke et al. in prep red=pairs; blue=N>2; size  log (  )  log (halo mass) Voronoi-based methods can also be used to identify clusters and groups of galaxies (Marinoni et al. 2002). DEEP2 group catalogs in two of our pointings will be published shortly. This will allow both the study of group property distributions and of group vs. field galaxies. red=absorption-dominated

Now looking at group correlations and void statistics… Coil et al. in prep Group-group correlation function is larger than the galaxy- galaxy correlation function. Field galaxies are less clustered than the full galaxy sample, which is less clustered than galaxies in groups.

Conclusions 1. r 0 ~3.5 Mpc/h at z~1, b~ for DEEP2 galaxies. 2. Red, passively-evolving galaxies have larger fingers of God and r 0 than blue, star-forming galaxies at z~1. 3. See some luminosity-dependence in the clustering strength. 4. Strong dependence of angular clustering on observed color: red galaxies at z~0.8 have r 0 ~6.5 Mpc/h blue galaxies at z>1.4 have r 0 >~5 Mpc/h Galaxy Clustering: Environment: 1. Color and OII EW correlate strongly with local environment at z~1. 2. Find a population of bright blue galaxies in the densest environments at z~1 which do not exist at z~0 - central cluster galaxies?