Constraints on ultraviolet absorption in the intracluster medium of Abell 1030

Abstract

We present results from an extensive HST spectroscopic search for UV absorption lines in the spectrum of the quasar B2 1028+313, which is associated with the central dominant galaxy in the cluster Abell 1030 (z=0.178). This is one of the brightest known UV continuum sources located in a cluster, and therefore provides an ideal opportunity to obtain stringent constraints on the column densities of any cool absorbing gas that may be associated with the intracluster medium (ICM). Our HST spectra were obtained with the FOS and GHRS, and provide continuous coverage at rest-frame wavelengths from ~975 to 4060°A, thereby allowing the investigation of many different elements and ionization levels. We utilize a new technique that involves simultaneous fitting of large numbers of different transitions for each species, thereby yielding more robust constraints on column densities than can be obtained from a single transition. This method yields upper limits of ~<10^11−10^13 cm^−2 on the column densities of a wide range of molecular, atomic and ionized species that may be associated with the ICM. We also discuss a possible Ly-alpha and C IV absorption system associated with the quasar. We discuss the implications of the upper limits on cool intracluster gas in the context of the physical properties of the ICM and its relationship to the quasar (Refer to PDF file for exact formulas).