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Keck Observations of Candidate Ultra-Luminous X-ray Sources

Published online by Cambridge University Press:  12 May 2006

Diane Sonya Wong ,
Ryan Chornock  and
Alexei V. Filippenko
Diane Sonya Wong
Affiliation:
Astronomy Department, 601 Campbell Hall, University of California, Berkeley, CA 94720 USA email: dianew@astro.berkeley.edu
Ryan Chornock
Affiliation:
Astronomy Department, 601 Campbell Hall, University of California, Berkeley, CA 94720 USA email: dianew@astro.berkeley.edu
Alexei V. Filippenko
Affiliation:
Astronomy Department, 601 Campbell Hall, University of California, Berkeley, CA 94720 USA email: dianew@astro.berkeley.edu
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Abstract

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We present results of optical follow-up observations of candidate ultra-luminous X-ray sources (ULXs). Using Keck optical spectroscopy, 17 of the candidates from the Colbert & Ptak (2002) catalog have been identified; this is one of the largest sets of optical identifications of such objects thus far. 15 are background active galactic nuclei (AGN); 2 are foreground stars in our Galaxy. These findings are compared with background and foreground object expectations, as derived from log $N$-log $S$ relations. Also, the results are briefly discussed in terms of the spiral-galaxy/ULX connection.

Keywords

black hole physicscatalogsgalaxies: distances and redshiftsgalaxies: individual (NGC 720, NGC 1316, NGC 1365, NGC 1399, NGC 2775, NGC 3266, IC 2597, NGC 3923, NGC 4151, NGC 4373, NGC 5128)quasars: generalX-rays: galaxies