Journal Article

Measurement of dwarf galaxies in the rich clusters Abell 665 and 963 at z=0.2

Neil Trentham

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 295, issue 2, pages 360-376
Published in print April 1998 | ISSN: 0035-8711
Published online April 1998 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1046/j.1365-8711.1998.01242.x
Measurement of dwarf galaxies in the rich clusters Abell 665 and 963 at z=0.2

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Abstract

We show that the luminosity functions of the distant rich clusters Abell 665 (z=0.182) and Abell 963 (z=0.206) are flat or gradually rising down to MR=−14, with α≈−1.2±0.4 [here α is the logarithmic slope of the luminosity function: φ(L)∝Lα at the faint end]. We do not confirm the steep luminosity functions (α≤−1.8) that have been recently proposed for these two clusters.

Several technical points are discussed in detail. In particular, we compute the corrections to the background contamination caused by gravitational lensing from the cluster dark matter, and show that the corrections are small unless we wish to determine variations in the luminosity function on small scales.

Recent observations have also shown that the field galaxy luminosity function at z≈0.2 is also shallow between MB=−19 and MB=−13. Abell 665 and 963 are two of the richest clusters known at that redshift. We therefore propose that the galaxy luminosity function might be universal in this magnitude range at z=0.2.

The dwarf galaxies that we see in Abell 665 have a colour distribution that is strongly peaked at BR=1.9. We compute K-corrections based on the spectral energy distributions of local galaxies, and show that these are probably dwarf spheroidal galaxies. This might suggest that the dwarf spheroidal population observed in Virgo already existed at z=0.2.

Keywords: galaxies: clusters: general; galaxies: clusters: individual: Abell 665; galaxies: clusters: individual: Abell 963; galaxies: luminosity function, mass function; gravitational lensing

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Subjects: Astronomy and Astrophysics

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