Poster Presentation Astronomical Society of Australia Annual Scientific Meeting including HWWS 2013

Searching for Intermediate Mass Black Holes in Early Type Galaxies Featuring Prominent Dust Lanes (#201)

Eromanga Adermann 1 , Sean Farrell 1 , Anne Green 1
  1. Sydney Institute for Astronomy, Redfern, NSW, Australia

Current theories suggest that intermediate mass black holes (~100 - 100,000 solar masses) played an important role in the formation of supermassive black holes. The study of intermediate mass black holes may therefore shed light on how supermassive black holes formed and evolved. One of the most promising methods for identifying intermediate mass black holes is through observations of the X-ray emission produced by accretion processes, though X-ray luminosities apparently above the Eddington limit for a low mass black hole can theoretically be produced by high mass X-ray binaries containing stellar mass black holes, accreting at very high rates and possibly emitting anisotropically. Though convincing observational evidence for the existence of intermediate mass black holes has thus far been sparse, the ultraluminous X-ray source HLX-1, located in the dusty early type galaxy ESO 243-49, is a very strong candidate, with an X-ray luminosity far in excess of the Eddington limit for a stellar mass black hole. Recent studies have indicated that HLX-1 is the remnant of a dwarf galaxy that was accreted < 200 Myr ago by ESO 243-49, suggesting that intermediate mass black holes may be the result of galaxy interaction. We sought to explore this idea further by searching for non-nuclear X-ray sources with luminosities above the stellar mass black hole Eddington limit in early type galaxies with prominent dust lanes (such as those present in ESO 243-49), which are believed to be traces of recent minor mergers. The low star formation rates in these galaxies mean that any such sources are unlikely to be extreme high mass X-ray binaries containing stellar mass black holes, and would thus constitute excellent intermediate mass black hole candidates. Here we present the results of our search for active intermediate mass black hole candidates in early type galaxies with prominent dust lanes, performed using archival XMM-Newton and Chandra X-ray data in a sample of galaxies taken from GalaxyZoo.