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arXiv · 1710.02360

Galaxy overdensities around 3C radio galaxies and quasars at $1<z<2.5$ revealed by Spitzer $3.6/4.5\mu$m and Pan-STARRS

Z. Ghaffari·Ch. Westhues·M. Haas·R. Chini·S. P. Willner·M. L. N. Ashby·B. J. Wilkes
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Abstract

Luminous radio sources are thought to lie in galaxy clusters or proto-clusters. The complete sample of 64 high-redshift 3C sources at $1 3\sigma$) within 30" ($\sim$250 kpc) projected distance from the radio source compared to the surrounding galaxy densities measured in the $50''-120''$ annulus. The Pan-STARRS/IRAC cut reveals higher average overdensities than the IRAC1/2 cut and also a decline of overdensities at $z>1.4$. To infer the nature of the cluster members, we rerun the analysis using a stronger IRAC1/2 cut $[3.6] - [4.5] < -0.1$ which removes $1<z<1.4$ passive ellipticals but not star-forming galaxies. For the strong cut, the overdensities, on average, completely disappear at $1<z<1.4$. We therefore suggest that the 4.5$\mu$m detected cluster member galaxies are mainly passive ellipticals.

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Z. Ghaffari, Ch. Westhues, M. Haas, R. Chini, S. P. Willner, M. L. N. Ashby, B. J. Wilkes. 2017-10-06. Galaxy overdensities around 3C radio galaxies and quasars at $1<z<2.5$ revealed by Spitzer $3.6/4.5\mu$m and Pan-STARRS. https://doi.org/10.1002/asna.201713389

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