A. Ptak and E. Colbert 2004 ApJ 606 291 doi:10.1086/382998
A. Ptak1 and E. Colbert1,2
Show affiliationsWe present a statistical analysis of the properties of galaxies containing ultraluminous X-ray objects (ULXs). Our primary goal is to establish the fraction of galaxies containing a ULX as a function of ULX luminosity. Our sample is based on ROSAT HRI observations of galaxies. We find that ~12% of galaxies contain at least one ULX with LX > 1039 ergs s-1, and ~1% of galaxies contain at least one ULX with LX > 1040 ergs s-1. These ULX frequencies are lower limits, since ROSAT HRI observations would miss absorbed ULXs (i.e., with NH
1021 cm-2) and those within ~10'' of the nucleus (due to the positional error circle of the ROSAT HRI). The Hubble type distribution of galaxies with a ULX differs significantly from the distribution of types for nearby Third Reference Catalog galaxies but does not differ significantly from the galaxy type distribution of galaxies observed by the HRI in general. We find no increase in the mean far-infrared (FIR) luminosity or FIR/K-band luminosity ratio for galaxies with a ULX relative to galaxies observed by the HRI in general; however, this result is also most likely biased by the soft bandpass of the HRI and the relatively low number of high star formation rate galaxies observed by the HRI with enough sensitivity to detect a ULX.
Issue 1 (2004 May 1)
Received 2003 October 31, accepted for publication 2004 January 19
A. Ptak and E. Colbert 2004 ApJ 606 291
Anjli Chhikara et al 1999 J. Phys.: Condens. Matter 11 L229
Jerzy Dajka et al 2007 J. Phys. A: Math. Theor. 40 F879
Hiroko Shinnaga et al 2004 ApJ 616 L47
L Li et al 2009 J. Phys. G: Nucl. Part. Phys. 36 125107
M Katsikini et al 2009 J. Phys.: Conf. Ser. 190 012065
Adam Doliwa 2007 J. Phys. A: Math. Theor. 40 12539
T Skrypnyk 2009 J. Phys. A: Math. Theor. 42 472004
M. Schneider et al 2009 Nucl. Fusion 49 125005
Helena Uusijärvi et al 2008 Phys. Med. Biol. 53 4369