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

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.

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

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

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

  3. 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. The DEEP2 Collaboration 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 U.C. Berkeley M. Davis (PI) M. Cooper B. Gerke R. Yan C. Conroy Steward Obs. A. Coil C. Willmer

  4. Large-Scale Structure in 2dF 220,000 galaxies in 1500 sq. degrees - z=0.1

  5. 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. 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 SDSS 2dF LCRS DEEP2 CFA+ SSRS z~0 z~1 PSCZ

  6. 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-3Mpc3 • 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

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

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

  9. Observing conditions in spring ‘04 were poor… The CFHT dome as seen from Gemini

  10. Redshift Maps in 4 Fields: z=0.7-1.3 Cone diagram of 1/12 of the full DEEP2 sample

  11. Galaxy Clustering Primer x(r) follows a ~power-law prescription locally: x(r) = (r0/r)g with r0~5 Mpc/h and g~1.8 r0 = 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

  12. 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. wp(rp) - clustering amplitude Galaxy separation (Mpc/h) 100 kpc/h 20 Mpc/h Coilet al. ApJ, astro-ph/0512233

  13. 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. Coilet al. 2006, ApJ

  14. 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., 2005 ApJ

  15. Bias: galaxy clustering/dark matter clustering Bias is expected to evolve with redshift, as first galaxies at high-z formed in densest regions. Observations + theory: z=3: b~4 z=0: b~1 LBGs SDSS Evolution of bias and dependence on scale and galaxy properties places strong constraints on galaxy formation theories. Galaxy formation sim. at z=3 by Kauffmann et al.grey=dark matter particlescolors=galaxies

  16. Luminosity/scale-dependence of bias Have now measured the scale-dependence and luminosity-dependence of galaxy bias at z=1 (assuming LCDM). 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

  17. Theoretical Modelling of x(r) Risa will talk about predicting the luminosity-dependent x(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.

  18. SDSS QSOs in DEEP2 fields 36 SDSS + 16 DEEP2 spectroscopic QSOs in the DEEP2 fields between z=0.7-1.4: Work done w/ Joe Hennawi + Jeff Newman Coil et al., ApJ submitted

  19. 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

  20. 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

  21. 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 x(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.

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