The Host Galaxies and Environment of Chandra ‐Selected Active Galactic Nuclei in the Deep ACS GTO Cluster Fields

Abstract

We present catalogs and images of optical counterparts to the Chandra-selected X-ray sources found in the fields of the five clusters RX J0152À1357, RX J0849+4452, RDCS J0910+5422, MS 1054À0321, and RDCS J1252À2927, which were imaged with the Advanced Camera for Surveys as part of the ACS Guaranteed Time Observer programs. A total of 98 X-ray sources fall within the ACS mosaics, and positive identifications are made for $96% of them, including confirmed cluster members. We classify the sources as active galactic nuclei (AGNs) or QSOs depending on their X-ray output. The log N (> S ) Ylog S test indicates a significant overdensity of X-ray sources in the RX J0152À 1357, RDCS J0910+5422, and MS 1054À0321 fields with respect to the CDF-S, suggesting an association of some X-ray sources with the large-scale structure of the clusters. From the asymmetry and concentration indices, $52% of the optical counterparts are early-type galaxies, $35% late-type, and the remainder irregular. A blue core is found in approximately half of the early-type galaxies. From visual examination, approximately 40% of the counterparts possess an unresolved nucleus, a common signature of nuclear activity. A majority of these nuclei are found in near faceon late-type galaxies although selection effects might be important. The X-ray to optical flux ratio of the nuclei correlates with the inclination angle of the late-type galaxies but not of the early types, as expected if dust is significant in the circumnuclear regions. The AGNs possess a $50% excess of nearby companions compared to the overall galaxy population in the same fields. The surface density of the X-ray sources is highest at projected radii of P1 Mpc from the cluster center and relatively flat at larger radii. We describe the morphology and environment of the cluster members and compare them with the other optical counterparts.

A CENSUS OF MID-INFRARED-SELECTED ACTIVE GALACTIC NUCLEI IN MASSIVE GALAXY CLUSTERS AT 0 ≲z≲ 1.3

“…We find that a third (4/12) of our cluster IR-AGNs are also known X-ray sources (Martel et al 2007;Johnson et al 2003), a fraction that is nominally consistent with results from the AGN and Galaxy Evolution Survey (AGES) where ∼50% of IR-AGNs are also X-ray sources ). However, it is worth mentioning here that X-ray flux limits are not the same among these studies, and so agreement on this ratio is not necessarily implied.…”

“…This cluster shows signs of having gone through a large-scale merger event recently as indicated by its X-ray emission, luminosity distribution, and weak-lensing profile (Jee et al 2005a). We detect two IR-AGNs in this cluster, both of which are classified as X-ray QSOs (Martel et al 2007); no other cluster galaxies are detected as X-ray sources. One of the IR+X-ray AGNs is about 800 kpc from the cluster core while the second appears to be in a merging system.…”

“…This unfortunately brings the "passive cloud" closer to the AGN wedge, possibly introducing contamination. Of the 29 RDCS 1252 members shown in Figure 3, 4 are inside the AGN wedge, of which 1 has been previously identified as an X-ray AGN (Martel et al 2007;Demarco et al 2007). Three of the four candidate IR-AGNs are hosted by morphologically irregular galaxies (Figure 4) that are likely to be gravitationally disrupted because of the large-scale cluster merger or by galaxy-galaxy mergers (HST image from Blakeslee et al 2003 andDemarco et al 2007).…”

THE X-RAY ZURICH ENVIRONMENTAL STUDY (X-ZENS). I.CHANDRAANDXMM-NEWTONOBSERVATIONS OF ACTIVE GALACTIC NUCLEI IN GALAXIES IN NEARBY GROUPS

“…There is evidence in a number of other studies (e.g., Ruderman & Ebeling 2005;Martini et al 2007;Martel et al 2007;Fassbender et al 2012) that AGN show a preference for the inner regions of massive clusters, at halo masses larger than the X-ZENS values, and that AGNs may possibly be associated with the brightest cluster members. There are however other studies which report opposite results, i.e., even possible AGN excesses in the outskirts of galaxy clusters (e.g., Gilmour et al 2009;Pentericci et al 2013).…”

VLT and ACS Observations of RDCS J1252.9−2927: Dynamical Structure and Galaxy Populations in a Massive Cluster atz= 1.237

“…A value of 99 has been assigned to unavailable photometry. The last column gives the morphological T-type (de Vaucouleurs et al 1976) of the galaxy, as determined by Postman et al (2005). upper right side of the plot, marked with a square, corresponds to an X-ray source at the cluster redshift (ID 174; see Rosati et al 2004;Martel et al 2007). Note the unusual morphology of this source (see Fig.…”