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The demographics of ultraluminous X‐ray sources
Author(s) -
Swartz D.A.
Publication year - 2011
Publication title -
astronomische nachrichten
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.394
H-Index - 63
eISSN - 1521-3994
pISSN - 0004-6337
DOI - 10.1002/asna.201011495
Subject(s) - physics , astrophysics , galaxy , luminosity , demographics , luminosity function , population , astronomy , medicine , demography , environmental health , sociology
Results of recent statistical studies of the population of ultraluminous X‐ray sources are presented. Special emphasis is placed on the outcome of a complete survey of 140 nearby galaxies hosting 114 ULXs. It is shown that ULXs are preferentially associated with young star‐forming regions but not necessarily with massive young clusters, that ULXs occur at a higher rate (per unit mass) in dwarf galaxies compared to giant galaxies and that ULXs rarely occur in galactic halos. If an upper limit to the luminosity of ULXs exists, then it must be above several times 10 40 erg s –1 in the X‐ray band. The luminosity function is still too sparsely sampled above this luminosity for a more definitive statement to be made (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)