Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 1992
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992aas...18110501w&link_type=abstract
American Astronomical Society, 181st AAS Meeting, #105.01; Bulletin of the American Astronomical Society, Vol. 24, p.1290
Astronomy and Astrophysics
Astronomy
Scientific paper
Recent analyses of X-ray spectra from the Einstein Observatory have revealed evidence for significant levels of excess absorption over that expected from the Galaxy associated with some cluster cooling flows (White {et al. } 1991; Wang & Stocke 1992). These observations imply the presence of large quantities of cold absorbing material (Mcold ~ 10(11) --10(12) Msun) and could represent direct evidence for the large amounts of cool material which current cooling flow models predict. In addition, such large quantities of absorbing material could have a significant impact on the observed X-ray properties of cluster cooling flows. To assess this impact, we have calculated the emergent X-ray properties for a set of cooling flow models including the effects of accumulated cold gas on the transfer of radiation through the cluster. These models are steady--state, spherically symmetric, and exhibit inhomogeneous gas distributions with material cooling out of the flow over all radii. Our results indicate that the accumulated cold material can have a dramatic effect on the observed X-ray properties of the cluster, reducing the total X-ray luminosity, L_X, in the range 0.1--10 keV by as much as 25% compared to the optically thin case. In the central regions of the flow (r < 1 kpc), the effects are even more extreme with absorption levels reaching values of 70%. Spatially, the opacity due to the cold gas results in X-ray surface brightness profiles which are much less centrally peaked than their optically thin counterparts with decreases between 40%--80% for radii less than 10 kpc. The surface brightness profiles for X-ray lines show similar effects. In addition, the continuum opacity produces spectral line profiles which are asymmetric and have reduced intensity on the ``blue'' side of the line. These photons correspond to emission from the far side of the cluster and must, consequently, traverse a greater pathlength than those on the near side. Finally, we find that the emergent optically thick X-ray spectra cannot be explained by a simple foreground absorption model.
Sarazin Craig L.
Wise Michael Wayne
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