X‐Ray Spectral Properties of the Cluster Abell 2029

Abstract

We have analyzed ASCA and ROSAT PSPC spectra and images of the galaxy cluster Abell 2029. The ASCA spectra of the cluster indicate that the gas temperature declines with radius. The PSPC image shows that the cluster is very regular and smooth. Also, there is no significant evidence for any irregularities in the temperature distribution in the cluster, as would be produced by a subcluster merger. These results suggest that A2029 is a relaxed cluster and that the gas is in hydrostatic equilibrium. We use the assumption of equilibrium to determine the gravitational mass of the cluster as a function of radius. At a radius of 16' (1.92 h−150 Mpc; H0 = 50 h50 km s-1 Mpc-1), the gravitational mass is Mtot = (9.42 ± 4.22) × 1014 h−150 M☉, while the mass of gas is Mgas = (2.52 ± 0.77) × 1014 h−5/250 M☉. The gas fraction is found to increase with radius; within a spherical radius of 16', the fraction is Mgas/Mtot = (0.26 ± 0.14) h−3/250 . The iron abundance in the gas is found to be 0.40 ± 0.04 solar. There is no significant evidence for any variation in the abundance with position in the cluster. The global X-ray spectra, central X-ray spectra, and ROSAT surface brightness all require a cooling flow at the cluster center. The global X-ray spectrum implies that the total cooling rate is 363+ 79−96 h−250 M☉ yr-1. The global X-ray spectra are consistent with the Galactic value for the soft X-ray absorption toward the cluster. White et al. and Allen & Fabian have suggested that there is significant excess absorption associated with the cooling flow in the cluster. The ROSAT PSPC spectra of the central regions of the cluster are inconsistent with a large value of foreground excess absorption. The upper limit on excess foreground absorption is 7.3 × 1019 cm-2. However, the spectra do not rule out a significant amount of intrinsic absorbing gas located within the cooling flow region.