Spatially Resolved Spectroscopy of the Globular Cluster RZ 2109 and the Nature of its Black Hole
Salzer, John J.; Kundu, Arunav; Zepf, Stephen E.; Maccarone, Thomas J.; Peacock, Mark B.; Gronwall, Caryl; Rhode, Katherine L.; Ciardullo, Robin; Stern, Daniel; Waters, Christopher Z.
United States, United Kingdom
Abstract
We present optical Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS) spectroscopy of RZ 2109, a globular cluster (GC) in the elliptical galaxy NGC 4472. This GC is notable for hosting an ultraluminous X-ray source as well as associated strong and broad [O III] λλ4959, 5007 emission. We show that the HST/STIS spectroscopy spatially resolves the [O III] emission in RZ 2109. While we are unable to make a precise determination of the morphology of the emission-line nebula, the best-fitting models all require that the [O III] λ5007 emission has a half-light radius in the range 3-7 pc. The extended nature of the [O III] λ5007 emission is inconsistent with published models that invoke an intermediate-mass black hole origin. It is also inconsistent with the ionization of ejecta from a nova in the cluster. The spatial scale of the nebula could be produced via the photoionization of a strong wind driven from a stellar mass black hole accreting at roughly its Eddington rate.
Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555.