Constraints on the Size Evolution of Brightest Cluster Galaxies

Abstract

We measure the luminosity profiles of 16 brightest cluster galaxies (BCGs) at 0.4 < z < 0.8 using high resolution F160W NICMOS and F814W WFPC2 HST imaging. The heterogeneous sample is drawn from a variety of surveys: seven from clusters in the Einstein Medium Sensitivity Survey (EMSS; Gioia & Luppino 1994), five from the Las Campanas Distant Cluster Survey and its northern hemisphere precursor (LCDCS; Dalcanton et al. 1997;Gonzalez et al. 2001;Nelson et al. 2001a), and the remaining four from traditional optical surveys (Spinrad 1980;Koo 1981;Gunn et al. 1986;Couch et al. 1991). We find that the surface brightness profiles of all but three of these BCGs are well described by a standard de Vaucouleurs (r 1/4 ) profile out to at least ∼ 2r e and that the biweight-estimated NICMOS effective radius of our high redshift BCGs (r e = 8.3 ± 1.4 kpc for H 0 = 80 km s −1 Mpc −1 , Ω m = 0.2, Ω Λ = 0.0) is ∼ 2 times smaller than that measured for a local BCG sample (Graham et al. 1996). If high redshift BCGs are in dynamical equilibrium and satisfy the same scaling relations as low redshift ones, this change in size would correspond to a mass growth of a factor of 2 since z ∼ 0.5. However, the biweight-estimated WFPC2 effective radius of our sample is 18 ± 5.1 kpc, which is fully consistent with the local sample. While we can rule out mass accretion rates higher than a factor of 2 in our sample, the discrepancy between our NICMOS and WFPC2 results, which after various tests we describe appears to be physical, does not yet allow us to place strong constraints on accretion rates below that level.

Fossil groups origins

“…There is no extra light over the Sèrsic profile in the outermost regions of the galaxy. This indicates that this galaxy is not a cD galaxy (see Graham et al 1996;Nelson et al 2002;Gonzalez et al 2005;Patel et al 2006;Seigar et al 2007;Vikram et al 2010). It is also interesting to note that the fitted Sèrsic profile has n ∼ 2.…”

EVOLUTION OF BRIGHTEST CLUSTER GALAXY STRUCTURAL PARAMETERS IN THE LAST ∼6 Gyr: FEEDBACK PROCESSES VERSUS MERGER EVENTS

“…A number of works (Caon et al 1993;Graham et al 1996;Patel et al 2006) argued that a much better model to fit the surface brightness of the BCG comes from a Sérsic profile rather than a de Vaucouleur profile, since the universality of the latter is uncertain. However, many recent works have shown evidence that the BCG outermost regions cannot be described by a Sérsic model and to provide a satisfactory fit, the introduction of at least two components is necessary (Nelson et al 2002;Gonzalez et al 2003Gonzalez et al , 2005Seigar et al 2007;Liu et al 2008).…”

“…However, Mancini et al (2010) have presented discrepant results by showing that some high-redshift massive ellipticals have similar sizes to local ones. As long as BCGs are concerned, Nelson et al (2002) and Bernardi (2009) Recently, it has been discovered that the Sérsic shape parameters of early-type galaxies have also evolved during the last Gyr, being larger for nearby galaxies (Vikram et al 2009;van Dokkum et al 2010). Indeed, although the mass of massive early-type galaxies has grown from z ∼ 2 until today, this mass growth has been focused on their external regions (van Dokkum et al 2010).…”

“…For instance, Aragón-Salamanca et al (1998) found that BCG galaxies have grown their masses in the last 8 Gyr. Nelson et al (2002) reported a growth of ∼2 at z ∼ 0.5 and Bernardi (2009) showed that BCGs at z ∼ 0.25 are 70% smaller in size than nearby ones.…”

The DEEP Groth Strip Survey. II. Hubble Space Telescope Structural Parameters of Galaxies in the Groth Strip

“…The bulge+disk model adopted here is not fundamentally new, but GIM2D offers an independent check of other galaxy classification works by including a set of extended features (Sérsic bulge profile, a comprehensive but by all means not exhaustive set of image asymmetry indices, three different fitting methods) and a different fitting algorithm. GIM2D has already been used in a variety of HST and ground-based distant galaxy studies: the optical structure of intermediate-redshift compact narrow emission line galaxies (Guzmán et al 1998), the quantitative morphology of Hubble Deep Field North galaxies (Marleau & Simard 1998), the NICMOS structure of a spiral galaxy lens at z ¼ 0:4 (Maller et al 2000), the luminosity-size relation of field disk galaxies from z ¼ 0:1 to z ¼ 1:1 (Simard et al 1999), the number density and luminosity function of E/SO galaxies to zd1 (Im et al 2002), the fundamental plane of field absorption-line galaxies out to z $ 1 (Gebhardt et al 2002), tests of hierarchical galaxy evolution models (L. Simard et al 2002, in preparation), the colors of luminous bulges at z $ 1 (D. C. Koo et al 2002, in preparation), the galaxy populations of poor, X-ray selected groups of galaxies (Tran et al 2001) and of high and low X-ray luminosity galaxy clusters (Balogh et al 2002), and the size evolution of high-redshift brightest cluster galaxies (Nelson et al 2002).…”