An extension of the SHARC survey

TL;DR

This paper reports on follow-up observations of X-ray candidates from the SHARC survey, identifying several distant galaxy clusters, QSOs, and other structures, highlighting the importance of wide-field X-ray telescopes for future studies.

Contribution

It extends the SHARC survey by providing optical and X-ray follow-up data, identifying new distant galaxy clusters and clarifying the nature of X-ray sources.

Findings

Identified galaxy clusters at redshifts z~0.28 to 0.53.

Detected several QSOs among the X-ray sources.

Highlighted the need for wide field X-ray telescopes.

Abstract

We report on our search for distant clusters of galaxies based on optical and X-ray follow up observations of X-ray candidates from the SHARC survey. Based on the assumption that the absence of bright optical or radio counterparts to possibly extended X-ray sources could be distant clusters. We have obtained deep optical images and redshifts for several of these objects and analyzed archive XMM-Newton or Chandra data where applicable. In our list of candidate clusters, two are probably galaxy structures at redshifts of z$\sim$0.51 and 0.28. Seven other structures are possibly galaxy clusters between z$\sim$0.3 and 1. Three sources are identified with QSOs and are thus likely to be X-ray point sources, and six more also probably fall in this category. One X-ray source is spurious or variable. For 17 other sources, the data are too sparse at this time to put forward any hypothesis on their nature. We also serendipitously detected a cluster at z=0.53 and another galaxy concentration which is probably a structure with a redshift in the [0.15-0.6] range. We discuss these results within the context of future space missions to demonstrate the necessity of a wide field of view telescope optimized for the 0.5-2 keV range.