Abstract
Adami et al. (2010) have detected several cluster candidates at z>0.5 as part of a systematic search for clusters in the Canada France Hawaii Telescope Legacy Survey, based on photometric redshifts. We focus here on two of them, located in the D3 field: D3-6 and D3-43. We have obtained spectroscopy with Gemini/GMOS and measured redshifts for 23 and 14 galaxies in the two structures. These redshifts were combined with those available in the literature. A dynamical and a weak lensing analysis were also performed, together with the study of X-ray Chandra archive data. Cluster D3-6 is found to be a single structure of 8 spectroscopically confirmed members at an average redshift z=0.607, with a velocity dispersion of 423 km/s. It appears to be a relatively low mass cluster. D3-43-S3 has 46 spectroscopically confirmed members at an average redshift z=0.739. It can be decomposed into two main substructures, having a velocity dispersion of about 600 and 350 km/s. An explanation to the fact that D3-43-S3 is detected through weak lensing (only marginally, at the ~3sigma level) but not in X-rays could be that the two substructures are just beginning to merge more or less along the line of sight. We also show that D3-6 and D3-43-S3 have similar global galaxy luminosity functions, stellar mass functions, and star formation rate (SFR) distributions. The only differences are that D3-6 exhibits a lack of faint early type galaxies, a deficit of extremely high stellar mass galaxies compared to D3-43-S3, and an excess of very high SFR galaxies. This study shows the power of techniques based on photometric redshifts to detect low to moderately massive structures, even at z~0.75.
Highlights
Galaxy evolution is still a major topic in cosmology because of the complexity of the processes involved
We propose adding our contribution to this problem through spectroscopy and photometry of candidate cluster galaxies observed with GEMINI/GMOS and primarily detected from CFHTLS survey photometric redshift catalogues
We performed the same Kolmogorov-Smirnov tests and found that for the D3-6 cluster, the probability for the early and late-type galaxy luminosity functions to originate from the same parent distribution was higher than 99% for 0% of the realisations, and higher than 75% for only 63% of the realisations
Summary
Galaxy evolution is still a major topic in cosmology because of the complexity of the processes involved. According e.g. to Mateus et al (2007), galaxy evolution is accelerated in denser environments. We propose adding our contribution to this problem through spectroscopy and photometry of candidate cluster galaxies observed with GEMINI/GMOS and primarily detected from CFHTLS survey photometric redshift catalogues. In this framework, Adami et al (2010) have published a catalogue of ∼1200 cluster candidates from public photometric redshifts (obtained following Ilbert et al 2006; see Coupon et al 2009) of the CFHTLS data release T0004 in the D2, D3, D4, W1, W3, and W4 regions.
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