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Date and Time of the Query: 2019-06-17 T16:37:28 PDT
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For refcode 2001ApJ...560..187O:
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Copyright by American Astronomical Society. Reproduced by permission
2001ApJ...560..187O FUSE Observations of Cooling-Flow Gas in the Galaxy Clusters A1795 and A2597 W. R. Oegerle, L. Cowie, A. Davidsen, E. Hu, J. Hutchings, E. Murphy, K. Sembach, and B. Woodgate Received 2001 April 25; accepted 2001 June 15 ABSTRACT We present far-ultraviolet spectroscopy of the cores of the massive cooling-flow clusters Abell 1795 and 2597, obtained with the Far Ultraviolet Spectroscopic Explorer. As the intracluster gas cools through 3 x 10^5^ K, it should emit strongly in the O VI {lambda}{lambda}1032, 1038 resonance lines. We report the detection of O VI {lambda}1032 emission in A2597, with a line flux of (1.35 +/- 0.35) x 10^-15^ ergs cm^-2^ s^-1^, as well as detection of emission from C III {lambda}977. A marginal detection of C III {lambda}977 emission is also reported for A1795. These observations provide evidence for a direct link between the hot (10^7^ K) cooling-flow gas and the cool (10^4^ K) gas in the optical emission line filaments. Assuming simple cooling-flow models, the O VI line flux in A2597 corresponds to a mass deposition rate of ~40 M_sun_ yr^-1^ within the central 36 kpc. Emission from O VI {lambda}1032 was not detected in A1795, with an upper limit of 1.5 x 10^-15^ ergs cm^-2^ s^-1^, corresponding to a limit on the mass cooling-flow rate of M^dot^(28 kpc) < 28 M_sun_ yr^-1^. We have considered several explanations for the lack of detection of O VI emission in A1795 and the weaker than expected flux in A2597, including extinction by dust in the outer cluster and quenching of thermal conduction by magnetic fields. We conclude that a turbulent mixing model, with some dust extinction, could explain our O VI results while also accounting for the puzzling lack of emission by Fe XVII in cluster cooling flows. Subject headings: cooling flows - galaxies: clusters: individual (Abell 1795, Abell 2597) - intergalactic medium - ultraviolet: galaxies
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