SIMBAD references

2000MNRAS.317..720B - Mon. Not. R. Astron. Soc., 317, 720-736 (2000/September-3)

The cluster environments of the z∼1 3CR radio galaxies.


Abstract (from CDS):

An analysis of the environments around a sample of 28 3CR radio galaxies with redshifts 0.6<z<1.8 is presented, based primarily upon K-band images down to K∼20 taken using the UK Infrared Telescope (UKIRT). A net overdensity of K-band galaxies is found in the fields of the radio galaxies, with the mean excess counts being comparable to that expected for clusters of Abell Class 0 richness. A sharp peak is found in the angular cross-correlation amplitude centred on the radio galaxies that, for reasonable assumptions about the luminosity function of the galaxies, corresponds to a spatial cross-correlation amplitude between those determined for low-redshift Abell Class 0 and 1 clusters.

These data are complemented by J-band images also from UKIRT, and by optical images from the Hubble Space Telescope. The fields of the lower redshift (z≲0.9) radio galaxies in the sample generally show well-defined near-infrared colour-magnitude relations with little scatter, indicating a significant number of galaxies at the redshift of the radio galaxy; the relations involving colours at shorter wavelengths than the 4000Å break show considerably greater scatter, suggesting that many of the cluster galaxies have low levels of recent or on-going star formation. At higher redshifts the colour-magnitude sequences are less prominent owing to the increased field galaxy contribution at faint magnitudes, but there is a statistical excess of galaxies with the very red infrared colours (J-K≳1.75) expected of old cluster galaxies at these redshifts.

Although these results are appropriate for the mean of all of the radio galaxy fields, there exist large field-to-field variations in the richness of the environments. Many, but certainly not all, powerful z∼1 radio galaxies lie in (proto)cluster environments.

Abstract Copyright: 2000, Royal Astronomical Society

Journal keyword(s): galaxies: active - galaxies: clusters: general - galaxies: luminosity function, mass function - radio continuum: galaxies

Simbad objects: 31

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