TheK-band luminosity functions of cluster galaxies

Abstract

We derive the galaxy luminosity function in the K s band for galaxies in 24 clusters to provide a local reference for higher redshift studies and to analyse how and if the luminosity function varies according to environment and cluster properties. We use new, deep K band imaging and match the photometry to available redshift information and to optical photometry from the SDSS or the UKST/POSS: > 80% of the galaxies to K ∼ 14.5 have measured redshifts. We derive composite luminosity functions, for the entire sample and for cluster subsamples . We consider the luminosity functions for red sequence and blue cloud galaxies. The full composite luminosity function has K * = 12.79 ± 0.14 (M K = −24.81) and α = −1.41 ± 0.10. We find that K * is largely unaffected by the environment but that the slope α increases towards lower mass clusters and clusters with Bautz-Morgan type < II. The red sequence luminosity function seems to be approximately universal (within errors) in all environments: it has parameters K * = 13.16 ± 0.15 (M K = −24.44) and α = −1.00 ± 0.12 (for all galaxies). Blue galaxies do not show a good fit to a Schechter function, but the best values for its parameters are K * = 13.51 ± 0.41 (M K = −24.09) and α = −1.60 ± 0.29: we do not have enough statistics to consider environmental variations for these galaxies. We find some evidence that K * in clusters is brighter than in the field and α is steeper, but note this comparison is based (for the field) on 2MASS photometry, while our data are considerably deeper.

Environmental effects on the UV upturn in local clusters of galaxies

“…Top: UV colours (FUV-V on the left and NUV-V on the right) plotted vs cluster velocity dispersion for all galaxies in the 2dF cluster sample of De Propris (2017). Bottom: UV colours (FUV-r on the left and NUV-r on the right) plotted vs cluster X-ray luminosity in the ROSAT soft band (0.5-2 KeV) for all galaxies in the 2dF cluster sample of De Propris (2017). We also show data from the literature (Ali et al 2018a) for Coma and Perseus.…”

“…This also indicates that the large He-enhancement that leads to the eventual UV upturn in a sub-population of the main sequence in ETGs must also occur intrinsically within the galaxies and at very early times. Propris (2017). Bottom: UV colours (FUV-r on the left and NUV-r on the right) plotted vs ∆V /σ.…”

“…In our previous papers (De Propris 2017; De Propris et al 2018) we have identified galaxies on the red sequence and blue cloud by fitting a straight line to the colour-magnitude relation (in each cluster, separately) using a minimum absolute deviation method that discriminates against outliers (see De Propris 2017;De Propris et al 2018 for details). The 1σ scatter in g −r for red sequence galaxies was measured to be 0.05 mag.…”

Galaxies in X-ray selected clusters and groups in Dark Energy Survey data – II. Hierarchical Bayesian modelling of the red-sequence galaxy luminosity function

“…The Sloan Digital Sky Survey (SDSS 2 ) has enabled detailed analysis of the cluster LFs (or CLFs) with the identification of tens of thousands of clusters to redshift 0.5 (Yang et al 2008;Hansen et al 2009). Above redshift 0.5, most studies have been performed with relatively small samples containing a handful of clusters or groups (Andreon 2008;Rudnick et al 2009;Crawford et al 2009;De Propris et al 2013;Martinet et al 2015;De Propris 2017) and wide field surveys that are more sensitive than SDSS have just provided an opportunity to reinvigorate such analyses (Sarron et al 2018).…”

Hubble Deep Fields

“…Most of this work has concentrated on rich cluster environments, and is not reviewed here except to note that most observers have favored the broad interpretation of quiescent, nearly passive evolution among cluster ellipticals out to z ≈ 1 (e.g. Aragón-Salamanca et al 1993;Stanford et al 1995Stanford et al , 1998Ellis et al 1997;van Dokkum et al 1998;De Propris et al 1999).…”