Clusters, Galaxies and the COSMOS
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Transcript of 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
Berian James (IfA Edinburgh)
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)
COSMOS & Large-scale structure 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.
VLA
Spitzer
HST (ACS)
Subaru
UKIRT
ESO-VLT
CHFT
NOAO
Galex
XMM
Chandra
Scoville et al., astro-ph/0612305
Berian James (IfA Edinburgh)
Data product: Catalogue of approximately 150 cluster locations, including photometric redshifts.
Clusters and galaxy groups VLA
Spitzer
HST (ACS)
Subaru
UKIRT
ESO-VLT
CHFT
NOAO
Galex
XMM
Chandra
e.g. Finoguenov et al., astro-ph/0612360
Berian James (IfA Edinburgh)
Optical galaxies 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.
VLA
Spitzer
HST (ACS)
Subaru
UKIRT
ESO-VLT
CFHT
NOAO
Galex
XMM
Chandra
e.g. Capak et al., astro-ph/0704.2430
Berian James (IfA Edinburgh)
The galaxy-cluster cross-correlation
Berian James (IfA Edinburgh)
Projected cross-correlation function
Phleps et al.., A&A 468 113
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)
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.
Separation
Corr
ela
tion
am
plit
ud
e
Berian James (IfA Edinburgh)
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.
z increasing
M in
creasi
ng
Berian James (IfA Edinburgh)
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
z
M
Berian James (IfA Edinburgh)
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.