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J. Zahid (Uinv. CA Berkeley), M. DeCesar (Penn State U.), L. Kinnaman (Wittenberg U, OH), M. Rice (Wellesley College), K. Saucedo-McQuade (Oberlin College), T. Ghosh, E. Momjian, C. Salter (NAIC/Arecibo Observatory)
As an Arecibo REU observing project in June 2004, seven galaxies with z < 0.24 were observed in a search for absorption/emission in the 21-cm HI line and all four 18-cm transitions of the OH molecule.
Strong HI absorption was detected against the complex continuum emission from the rich galaxy cluster, Abell 2390. This massive cluster contains a powerful cooling flow.
Follow up higher-spectral resolution observations revealed five Gaussian components in the HI absoprtion spectrum of Abell 2390. The peak absorption is ~7.5 % of the observed continuum surface brightness of the cluster with the 3.3-arcmin Arecibo beam. The derived HI column density is NH ~3 \times 1019 Ts/f cm-2, where Ts is the HI spin temperature and f is the covering factor of the continuum emission by the neutral gas. With the broad Arecibo beam it is impossible to say against which continuum component/s the HI absorption occurs; hence, f is presently unknown.
We have also imaged the L-band continuum emission of the Abell 2390 using VLA A-array archival data. Within the well-known distributed continuum emission of the cluster, we found nine discrete sources on the arcsec scale, including the central cD galaxy.
Future GMRT and WSRT synthesis observations will allow us to map the distribution and the kinematics of the neutral hydrogen in this cluster at a higher spatial resolution. These observation will allow a detailed investigation as to whether the cool neutral gas is associated with one or more individual galaxies, or is a distributed intra-cluster phonomenon.
The Arecibo Observatory is part of the National Astronomy and Ionosphere Center, which is operated by Cornell University under a cooperative agreement with the National Science Foundation.
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.