SPIDERS: the spectroscopic follow-up of X-ray selected clusters of galaxies in SDSS-IV

• Published in: arXiv.org
• Main Authors: Clerc, Nicolas, Merloni, Andrea, Yu-Ying, Zhang, Finoguenov, Alexis, Dwelly, Tom, Nandra, Kirpal, Collins, Chris A, Dawson, Kyle, Jean-Paul Kneib, Rozo, Eduardo, Rykoff, Eli, Sadibekova, Tatyana, Brownstein, Joel R, Yen-Ting, Lin, Ridl, Jethro, Salvato, Mara, Schwope, Axel, Steinmetz, Matthias, Hee-Jong Seo, Tinker, Jeremy
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 31.08.2016
• Subjects: Active galactic nuclei; Algorithms; Cosmology; Dispersion; Galactic clusters; Galaxies; Large scale structure of the universe; Luminosity; Physics - Cosmology and Nongalactic Astrophysics; Sky surveys (astronomy); Universe; Workflow; XMM (spacecraft)
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1608.08963

SPIDERS (The SPectroscopic IDentification of eROSITA Sources) is a program dedicated to the homogeneous and complete spectroscopic follow-up of X-ray AGN and galaxy clusters over a large area (\(\sim\)7500 deg\(^2\)) of the extragalactic sky. SPIDERS is part of the SDSS-IV project, together with the Extended Baryon Oscillation Spectroscopic Survey (eBOSS) and the Time-Domain Spectroscopic Survey (TDSS). This paper describes the largest project within SPIDERS before the launch of eROSITA: an optical spectroscopic survey of X-ray selected, massive (\(\sim 10^{14}\) to \(10^{15}~M_{\odot}\)) galaxy clusters discovered in ROSAT and XMM-Newton imaging. The immediate aim is to determine precise (\(\Delta_z \sim 0.001\)) redshifts for 4,000-5,000 of these systems out to \(z \sim 0.6\). The scientific goal of the program is precision cosmology, using clusters as probes of large-scale structure in the expanding Universe. We present the cluster samples, target selection algorithms and observation strategies. We demonstrate the efficiency of selecting targets using a combination of SDSS imaging data, a robust red-sequence finder and a dedicated prioritization scheme. We describe a set of algorithms and work-flow developed to collate spectra and assign cluster membership, and to deliver catalogues of spectroscopically confirmed clusters. We discuss the relevance of line-of-sight velocity dispersion estimators for the richer systems. We illustrate our techniques by constructing a catalogue of 230 spectroscopically validated clusters (\(0.031 < z < 0.658\)), found in pilot observations. We discuss two potential science applications of the SPIDERS sample: the study of the X-ray luminosity-velocity dispersion (\(L_X-\sigma\)) relation and the building of stacked phase-space diagrams.