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Clusters, Galaxies and the COSMOS

Clusters, Galaxies and the COSMOS. J Berian James (IfA Edinburgh), John Peacock, Alexis Finoguenov, Henry Joy McCracken & Gigi Guzzo for the COSMOS collaboration. COSMOS – The Cosmic Evolution Survey.

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Clusters, Galaxies and the COSMOS

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  1. Clusters, Galaxies and the COSMOS J Berian James (IfA Edinburgh), John Peacock, Alexis Finoguenov, Henry Joy McCracken & Gigi Guzzo for the COSMOS collaboration

  2. COSMOS – The Cosmic Evolution Survey • The primary goal of COSMOS is to study the relationship between large-scale structure and the formation of galaxies, dark matter, and nuclear activity in galaxies. • 0.5 < z < 3 • 2 million objects (IAB ~ 27) • Volume ~ SDSS/2dFGRS Berian James (IfA Edinburgh)

  3. The assembly of galaxies, clusters and dark matter on mass scales up to 1014; Reconstruction of the dark matter distribution and content at z ~ 1.5; The redshift and environment evolution of galaxy morphology, merger rates and star formation; The evolution of AGN and dependence of black hole growth on galaxy morphology and environment; and The clustering, mass and luminosity distribution of the earliest galaxies, AGN and intergalactic gas at 3 < z < 6. COSMOS & Large-scale structure VLA Spitzer HST (ACS) Subaru UKIRT ESO-VLT CHFT NOAO Galex XMM Chandra Berian James (IfA Edinburgh) Scoville et al., astro-ph/0612305

  4. Clusters and galaxy groups • Data product: Catalogue of approximately 150 cluster locations, including photometric redshifts. VLA Spitzer HST (ACS) Subaru UKIRT ESO-VLT CHFT NOAO Galex XMM Chandra Berian James (IfA Edinburgh) e.g. Finoguenov et al., astro-ph/0612360

  5. Observations Subaru broad-bands (B, V, r+, i+, z+) Intermediate- and narrow-bands (redshift refinement and high-redshift galaxy search) Data products Photometric, flux-calibrated images (.05 mag rms) with absolute astrometry (0.1 x ACS pixel) over the full COSMOS field; Million-source photometric redshift catalogue. Optical galaxies VLA Spitzer HST (ACS) Subaru UKIRT ESO-VLT CFHT NOAO Galex XMM Chandra Berian James (IfA Edinburgh) e.g. Capak et al., astro-ph/0704.2430

  6. The galaxy-cluster cross-correlation Berian James (IfA Edinburgh)

  7. Projected cross-correlation function • Decompose the separation into line-of-sight (redshift) and transverse components; • The uncertainties in photometric redshifts cause distortion along line-of-sight; • To remove this effect, integrate along the line-of-sight. Berian James (IfA Edinburgh) Phleps et al.., A&A 468 113

  8. The galaxy-cluster cross-correlation • Using 110 clusters at 0.3 < z < 1 • Measurement is relative to cluster-random galaxy pairs; the latter reproduces the selection effects of the survey, but is otherwise Poisson-distributed. Correlation amplitude Separation Berian James (IfA Edinburgh)

  9. Evolution with mass and redshift • 3 redshift bins for 0 < z < 1.0 • 3 bins in log M from ~1012 to 1014 • For each bin, measure wp with just the clusters in that bin; • To examine the trend in clustering, compare the amplitude at a fixed value of rp. M increasing z increasing Berian James (IfA Edinburgh)

  10. Adaptive binning in the M-z plane • Division of the plane based on clusters available; • For each bin, measure wp with just the clusters in that bin; • Trends not obvious, but can be improved by optimising the number of clusters per bin M z Berian James (IfA Edinburgh)

  11. Summary • The cluster-galaxy correlation displays evolution with mass and with redshift; • But at higher redshift, the survey probes higher mass clusters, so how much of the redshift trend is really a trend in mass? • Can adaptive binning simultaneously capture the features of the trends in both mass and redshift? • The generation of random cluster catalogues would go some way to improving the result, by allowing the use of more sophisticated cross-correlation measures. Berian James (IfA Edinburgh)

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