AAS 195th Meeting, January 2000
Session 120. Clusters of Galaxies and Their Contents
Oral, Saturday, January 15, 2000, 10:00-11:30am, Centennial III

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[120.04] A Search for Intracluster Planetary Nebulae in the Virgo Cluster

J.J. Feldmeier (Penn State University)

Intracluster stars, i.e. stars outside of individual galaxies, are a sensitive measure of the poorly understood processes of galactic mergers, cluster accretion, and tidal-stripping that occur in galaxy clusters. Unfortunately, although the first detection of intracluster starlight occurred almost fifty years ago, research into their properties has been hampered by observational difficulties. Recently however, there have been multiple discoveries of individual intracluster planetary nebulae (IPN) in the nearby clusters of Virgo and Fornax. These objects provide us with a new tool to probe the strcuture and evolution of galaxy clusters.

IPN have a number of properties that make them excellent tracers of the intracluster starlight as a whole. The distribution of planetary nebulae closely follow the distribution of starlight in galaxies, so planetaries directly measure the amount of intracluster luminosity. Planetary nebulae also have a well-defined luminosity function allowing us to determine the spatial distribution of the intracluster stars. Finally, since planetaries are emission-line objects, their velocities can be determined readily, and information on the kinematics of the intracluster star population gained.

The goals of this work are to increase the sample of known IPN from a handful to a large number, and to determine their basic properties in the nearby, well-studied, Virgo Cluster of galaxies. In three years of observations, we have surveyed 4988 square arcminutes of the Virgo Cluster, and have detected over a hundred IPN candidates. From this data, we find that the intracluster starlight of Virgo 1) is luminous (at least 15% of the total starlight), 2) varies spatially, 3) is elongated along our line-of-sight, and 4) may be of moderate age and metallicity. Although some (\approx 20%) of the candidates are found to be z \approx 3.1 galaxies, the majority of the candidates appear to be genuine IPN. Future research will be discussed.

This work was partially funded by GO-0612.01-94A & GO-06731.01A-95A from the Space Telescope Science Institute.

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The author(s) of this abstract have provided an email address for comments about the abstract: johnf@astro.psu.edu

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