A systematic cross-search for radio/infrared counterparts of XMM-Newton sources

J. A. COMBI; J. F. ALBACETE COLOMBO; L. PELLIZZA; J. LÓPEZ-SANTIAGO; G. E. ROMERO; J. MARTÍ; A. J. MUÑOZ-ARJONILLA; E. SÁNCHEZ-AYASO; P. L. LUQUE-ESCAMILLA; J. R. SÁNCHEZ-SUTIL

ASTROPHYSICS AND SPACE SCIENCE

SPRINGER

Año: 2010

0004-640X

We present a catalog of cross-correlated radio, infrared and X-ray sources using a very restrictive selection criteria with an IDL-based code developed by us. The significance of the observed coincidences was evaluated throughMonte Carlo simulations of synthetic sources following a well-tested protocol. We found 3320 coincident radio/X-ray sources with a high statistical significance characterized by the sum of error-weighted coordinate differences. For 997 of them, 2MASS counterparts were found. The percentage of chance coincidences is less than 1%. X-ray hardness ratios of wellknown populations of objects were used to provide a crude representation of their X-ray spectrum and to make a preliminary diagnosis of the possible nature of unidentified X-ray sources. The results support the fact that the X-ray sky is largely dominated by Active Galactic Nuclei at high galactic latitudes (|b| > 10 deg). At low galactic latitudes (|b| < 10 deg) most of unidentified X-ray sources (~ 94%) lie at |b| < 2 deg. This result suggests that most of the unidentified sources found toward the Milky Way plane are galactic objects. Well-known and unidentified sources were classified in different tables with their corresponding radio/infrared and X-ray properties. These tables are intended as a useful tool for researchers interested in particular identifications.