Intracluster Planetary Nebulae in the Virgo Cluster. I. Initial Results

We report the initial results of a survey for intracluster planetary nebulaein the Virgo Cluster. In two 16' x 16' fields, we identify 69 and 16intracluster planetary nebula candidates, respectively. In a third 16' x 16'field near the central elliptical galaxy M87, we detect 75 planetary nebulacandidates, of which a substantial fraction are intracluster in nature. Byexamining the number of the planetaries detected in each field and the shape ofthe planetary nebula luminosity function, we show that 1) the intraclusterstarlight of Virgo is distributed non-uniformly, and varies between subclumps Aand B, 2) the Virgo Cluster core extends ~3 Mpc in front of M87, and thus iselongated along the line-of-sight, and 3) a minimum of 22% of Virgo's stellarluminosity resides between the galaxies in our fields, and that the true numbermay be considerably larger. We also use our planetary nebula data to argue thatthe intracluster stars in Virgo are likely derived from a population that is ofmoderate age and metallicity.