ROSAT X-ray Observations of the Cooling Flow Cluster A2597

Abstract

The cluster A2597 was observed in X-rays with the ROSAT PSPC and HRI detectors. The X-ray isophotes are oriented similarly to the optical isophotes of the central cD galaxy and to the isopleths of the galaxy distribution in the cluster, but are otherwise quite regular, suggesting that this cluster is reasonably relaxed and in hydrostatic equilibrium. The merged HRI and PSPC surface brightness profile is not adequately fit by a beta model because of the central X-ray surface brightness peak, indicating the presence of a cooling flow. If the central 108 arcsec in radius are excluded, an acceptable fit is found which gives beta = 0.64 but only an upper limit to the core radius, rcore < 78 arcsec. Within a radius of 2 Mpc, we found masses of Mgas = 1.2e14 Msun and Mtot = 6.5e14 Msun, and a gas mass fraction of about 19%. Both the overall cluster spectrum and the spatially resolved spectra within 300 kpc require the presence of both hot gas and a cooling flow in the spectrum. The spectrally determined total cooling rate of Mdot = 344 Msun/yr is in good agreement with those derived from analyses of the X-ray surface brightness profile from the Einstein IPC and the ROSAT HRI images. The ROSAT spatially resolved X-ray spectra indicate that the cooling component is distributed over the inner ~300 kpc in radius of the cluster. We do not detect any significant excess X-ray absorption toward the center of A2597, and we set a very conservative upper limit on the excess column in front of the cooling flow region of NH < 1.72e20 cm**-2.