Roger Bartlett | Searcharxiv

arXiv1997

Intracluster Stars and the Galactic Halos of Virgo

Planetary nebulae can be useful dynamical probes of elliptical galaxy halos, but progress thus far has been hampered by the small data samples available for study. In order to obtain a large sample of planetary nebulae for dynamical analysis, we have re-observed the giant elliptical galaxy M87 in the center of the Virgo Cluster. Surprisingly, we find that the M87 sample is contaminated by a significant fraction of intracluster objects. Follow up observations of three blank fields in the cluster confirm that a significant fraction of Virgo's starlight is intracluster. We discuss the implications of intracluster stars for studies of galaxy halos in clusters.

astro-ph↗

arXiv1997

The Planetary Nebula Luminosity Function of M87 and the Intracluster Stars of Virgo

We present the results of a wide-field [O III] $λ5007$ survey for planetary nebulae (PN) in M87 and its surrounding halo. We show that the planetary nebula luminosity function (PNLF) of M87's halo is unlike any PNLF observed to date, with a shape that differs from that of the empirical law at the 99.9% confidence level. In addition, we find that the PNLF of M87's outer halo differs from that of the galaxy's inner regions at a high degree of certainty ($\sim 92%$). We show that both these effects are most likely due to the existence of intracluster PN, many of which are foreground to M87. These intracluster objects explain the ``overluminous'' [O III] $λ5007$ sources previously identified by Jacoby, Ciardullo, & Ford (1990), and present us with a new tool with which to probe the morphological and dynamical properties of the cluster. By modifying the maximum likelihood procedures of Ciardullo et al (1989a) and using an assumed M31 distance of 770 Kpc (Freedman & Madore 1990), we derive a distance modulus to M87 of $30.79 \pm 0.16$ ($14.4 \pm 1.1$ Mpc).

astro-ph↗