The High-redshift Clusters Occupied by Bent Radio AGN (COBRA) Survey: Follow-up Optical Imaging

Abstract

Here we present new red sequence overdensity measurements for 77 fields in the high-z Clusters Occupied by Bent Radio AGN (COBRA) survey, based on r-and i-band imaging taken with Lowell Observatory's Discovery Channel Telescope. We observe 38 COBRA fields in r-band and 90 COBRA fields in i-band. By combining the r-and i-band photometry with our 3.6 µm and 4.5 µm Spitzer IRAC observations, we identify 39 red sequence cluster candidates that host a strong overdensity of galaxies when measuring the excess of red sequence galaxies relative to a background field. We initially treat the radio host as the cluster center and then determine a new cluster center based on the surface density of red sequence sources. Using our color selection, we identify which COBRA cluster candidates have strong red sequence populations. By removing foreground and background contaminants, we more securely determine which fields include cluster candidates with a higher significance than our singleband observations. Additionally, of the 77 fields we analyze with a redshift estimate, 26 include newly estimated photometric redshifts.

Jets in radio galaxies and quasars: an observational perspective

“…The WATs appear to be of higher radio luminosity and tend to be associated with the dominant galaxies in clusters, although not exclusively (e.g. Owen & Rudnick, 1976;Golden-Marx et al, 2019).…”

Multiwavelength view of SPT-CL J2106-5844

“…The morphology of the radio emission around the BCG suggests that it may be associated with a radio jet from the central AGN with mildly bent arms (Sakelliou & Merrifield 2000). Such sources are not uncommon in disturbed galaxy clusters, as the motion of a radio galaxy with respect to the intracluster gas can induce a significant bending of the radio lobes (see, e.g., Paterno-Mahler et al 2017, Garon et al 2019, Golden-Marx et al 2019, Moravec et al 2020. On the other hand, the southern diffuse emission C3 (Fig.…”

VLA resolves unexpected radio structures in the Perseus cluster of galaxies

“…As discussed in Section 4.1, the direction of the motion of bent-jet radio galaxies can usually be roughly estimated based on the orientation of the bent jetsalthough not necessarily in the case of NGC 1272. For instance, in samples of bent-jet radio galaxies (Sakelliou & Merrifield 2000;Golden-Marx et al 2019, 2020, the sources are sometimes identified as "incoming" or "outgoing". The existence of outgoing sources means they have survived an entire first passage through the cluster and persist after crossing the cluster center, where the ICM is turbulent and has a high density.…”

“…These large-scale bulk motions can also provide enough ram pressure to bend their radio jets (Begelman et al 1979). This could in particular explain the bending of the jets in wide-angle tail radio galaxies, which are mostly associated with large elliptical galaxies located at cluster centers (e.g., Owen & Rudnick 1976;O'Donoghue et al 1993, although not exclusively, see Sakelliou & Merrifield 2000;Wing & Blanton 2011;Garon et al 2019;Golden-Marx et al 2019), implying that radio galaxies' velocities through their host cluster's ICM may not be large enough to fully bend the galaxies' radio jets.…”