Luminosity distributions within rich clusters — I. A ubiquitous dwarf-rich luminosity function?

Abstract

From deep CCD observations of the cluster Abell 2554 we have recovered the cluster's luminosity distribution over a wide range of magnitude (−24 < M R < −16). We compare the derived A 2554 cluster luminosity function (at redshift 0.1) with that of the local Coma Cluster (A 1656) and the more distant (z = 0.2) cluster A 963. The distribution is remarkably similar for these three clusters of comparable richness and morphology. All show a flat (α = −1.0) luminosity function for the giant galaxies (−24 < M R < −19.5) which exhibits a sharp upturn (α ≈ −1.7) at some intermediate magnitude (M R ≃ −19) and continues to rise to the limits of existing data. We suggest that such a luminosity function may be ubiquitous among rich clusters and that a similar form may apply for poorer clusters and possibly the field as well. The three cluster dwarf LFs are seen over a range of lookback times covering a quarter of the age of the universe. Therefore the similarity between the three measured LFs seems to rule out strong evolution of the dwarf populations in rich cluster environments, at least out to z = 0.2, unless richness effects conspire to conceal evolutionary changes.

Do Clusters Contain a Large Population of Dwarf Galaxies?

“…1997 ;Wilson et al 1997 ;Smith et al 1997 ;Trentham 1997Trentham , 1998Driver et al 1998 ;Garilli et al 1999). In most of these studies, these and other authors have demonstrated using background subtraction procedures that galaxy clusters are dominated in number by a large population of faint galaxies.…”

Environmental Effects on the Faint End of the Luminosity Function

“…It was suggested by the results on A2554 (Smith et al 1997), that the dwarf population was more spatially extended than that of the giants, i.e. the dwarf to giant ratio increased outwards.…”

“…These studies suggest that the LF becomes steep (Schechter (1976) slope a < -1.5) in many clusters, faintwards of about MB = -17.5 or MR ~ -19 (for H 0 = 50 km s -1 Mpc -1 ), where (generally low surface brightness) dwarfs begin to dominate (e.g. Smith, Driver & Phillipps 1997;Trentham 1997a,b). Using deep CCD imaging from the Anglo-Australian Telescope, we have now extended this work (see , in order to examine the luminosity distribution in and across a variety of Abell and ACO clusters.…”

“…However we should note that these clusters were selected (from a larger unpublished sample) only if they had LFs well fitted by a single Schechter function. This obviously precludes clusters with steep LF turn-ups at intermediate magnitudes Smith et al 1997). Note that typical error bars (due to the combination of Poisson errors and background subtraction errors) are 10% in density and 20% in DGR for the denser regions, rising to 30% in density and 50% in DGR at the lowest densities (and hence object numbers).…”

Low Surface Brightness Galaxies in Deep Surveys

“…The other projection of the bivariate brightness distribution, the luminosity function (LF), has also seen some recent developments (Marzke et al 1998;Loveday 1997;Smith, Driver, and Phillipps 1997;Sawicki, Lin, and Yee 1997;Lin et al 1996). In particular there appears to be an emerging consensus that the faint end slope of the LF is steep: N(L) oc L~a with a £ -1.2.…”