1996/08/19 by J. J. Mohr, Margaret J. Geller, M. J. Geller +1 · 4 citations
Physics and Astronomy · #Abell 2744 #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Brightest cluster galaxy #Cluster (spacecraft) #Demography #Galaxies: Formation, Evolution, Phenomena #Galaxy #Galaxy cluster #Physics #Population #Redshift #Stellar, planetary, and galactic studies #Velocity dispersion #Virial mass #Virial theorem #astro-ph
paper · pdf · doi:10.1086/118144
22 pages, to appear in the Astronomical Journal, Nov 96
arxiv created 1996/08/19 · openalex publication_date 1996/11/01 · openalex created_date 2016/06/24 · arxiv updated 2016/08/30 · openalex updated_date 2026/08/05
We use 189 new radial velocities and R band CCD photometry to study the galaxy clusters Abell 2626 and Abell 2440. By combining these new optical constraints with archival x-ray images and gas temperature measurements, we investigate the dynamical nature of both systems. We derive masses, luminosity functions, and mass-to-light ratios. The symmetric x-ray emission from A2626 suggests a relaxed, single-component system; however, our sample of 159 redshifts reveals a complex, three-component cluster at cz ~ 17500 km/s. One of these components is a typical x-ray bright cluster, a second has a cluster-like galaxy population with a much lower central galaxy and gas density, and the third is a background structure with field galaxy composition. A comparison of the magnitude distributions within the two subclusters suggests that A2626 is a merger in progress (at 93% confidence). Virial masses and a composite luminosity function for a region with projected radius r= 1.5h-1^ Mpc yield a mass- to-light ratio M/LR_ ~ 610h. Analysis of the x-ray emission from the primary component yields a gas mass function of ~2.2h-3/2^% and a baryon fraction of ~3.4%. A radial infall model indicates that the virial mass may be an underestimate. The bimodal x-ray emission and elongated galaxy distribution of A2440 have been studied before (Baier 1979; Beers et al. 1991). With deeper, CCD R band photometry we demonstrate a striking correspondence between the galaxy and cluster gas distributions. The galaxy distribution has three main components, each associated with a giant elliptical galaxy. The two larger peaks in the galaxy distribution coincide with the primary peaks in the x-ray emission, and the third is associated with a significant x-ray surface brightness enhancement. We use this galaxy-gas correspondence, 48 redshifts, and the structure of the x-ray emission to argue that the subclusters are bound within a single system, and that the two primary components are beginning to merge. The composite luminosity function and estimates of the subcluster virial masses indicate a mass-to-light ratio in the range M/LR_ = 660h to 880h.