Optical counterparts to Ultraluminous X-ray sources Jeanette Gladstone - University of Alberta T. P. Roberts (U of Durham), A. D. Goulding (CfA) T. Cartwright & C. O. Heinke, (U of A), C. Copperwheat & A. J. Levan (U of Warwick), M. R. Goad (U of Leceister) Jeanette Gladstone - University of Alberta T. P. Roberts (U of Durham), A. D. Goulding (CfA) T. Cartwright & C. O. Heinke, (U of A), C. Copperwheat & A. J. Levan (U of Warwick), M. R. Goad (U of Leceister) University of AlbertaJeanette GladstoneX-ray Universe 2011 What are Ultraluminous X-ray sources? X-ray point source residing outside the nucleus of the galaxy Thought to be X-ray binaries, containing black hole L X > erg s -1 (above Eddington limit for 10 solar mass black hole) X-ray point source residing outside the nucleus of the galaxy Thought to be X-ray binaries, containing black hole L X > erg s -1 (above Eddington limit for 10 solar mass black hole) composite X-ray (red)/optical (blue & white) image of the spiral galaxy M74 (NASA/CXC/U. Michigan/J. Liu et al.) We know they contain black holes but, what are their masses? What option do we have to explain their nature? Why do we care? University of Alberta What are ULXs? Intermediate mass black holes Missing link in the mass scale Provide route to form super- massive black holes Provide insight into the formation of galaxies Stellar mass black holes Contain objects we can easily form Some of the most extreme accretors in our universe Provides a need for new accretion physics Jeanette GladstoneX-ray Universe 2011 Why do we care? Either way, we have something different and new to study After more than 30 years of study, we are currently unable to settle this in the X-ray band how about optical? After more than 30 years of study, we are currently unable to settle this in the X-ray band how about optical? University of AlbertaJeanette GladstoneX-ray Universe 2011 Identification of optical counterparts Can use unprecedented spatial resolution of the Chandra telescope Allows for more accurate positioning of sources Also need help of HST Can use unprecedented spatial resolution of the Chandra telescope Allows for more accurate positioning of sources Also need help of HST From Zampier et al 2004 showing 90% confidence radii for various X-ray instruments against and ESO 3.6m R-band image of NGC 1313 X-2 University of Alberta New search for stellar counterparts Search restricted