Optical Photometric Indicators of Galaxy Cluster Relaxation
[1];
[3];
[4];
[5]
- Stanford Univ., CA (United States); Ecole Normal Superieure, Paris (France)
- San Diego State Univ., CA (United States); Univ. of Colorado, Boulder, CO (United States)
- Stanford Univ., CA (United States). Kavli Institute for Particle Astrophysics & Cosmology
- Stanford Univ., CA (United States). Kavli Institute for Particle Astrophysics & Cosmology; SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)
- Stanford Univ., CA (United States). Kavli Institute for Particle Astrophysics & Cosmology; Chulalongkorn Univ., Bangkok (Thailand)
The most dynamically relaxed clusters of galaxies play a special role in cosmological studies as well as astrophysical studies of the intracluster medium (ICM) and active galactic nucleus feedback. While high-spatial-resolution imaging of the morphology of the ICM has long been the gold standard for establishing a cluster’s dynamical state, such data are not available from current or planned surveys, and thus require separate, pointed follow-up observations. With optical and/or near-IR photometric imaging, and red-sequence cluster finding results from those data, expected to be ubiquitously available for clusters discovered in upcoming optical and millimeter-wavelength surveys, it is worth asking how effectively photometric data alone can identify relaxed cluster candidates, before investing in, e.g., high-resolution X-ray observations. Here we assess the ability of several simple photometric measurements, based on the redMaPPer cluster finder run on Sloan Digital Sky Survey data, to reproduce X-ray classifications of dynamical state for an X-ray selected sample of massive clusters. We find that two simple metrics contrasting the bright central galaxy (BCG) to other cluster members can identify a complete sample of relaxed clusters with a purity of ~40% in our data set. Including minimal ICM information in the form of a center position increases the purity to ~60%. However, all three metrics depend critically on correctly identifying the BCG, which is presently a challenge for optical red-sequence cluster finders.
- Research Organization:
- SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC); National Science Foundation (NSF); Alfred P. Sloan Foundation; USDOE
- Grant/Contract Number:
- AC02-76SF00515
- OSTI ID:
- 2349569
- Alternate ID(s):
- OSTI ID: 2396964; OSTI ID: 2403396
- Journal Information:
- The Astrophysical Journal, Vol. 967, Issue 1; ISSN 0004-637X
- Publisher:
- IOP PublishingCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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