tokens: We wish to thank an anonymous referee for his/her helpful suggestions. I.P. acknowledges support by Chandra fund 16617814 contract GO2-13021X. The scientific results reported in this article are based on observations made by the Chandra and XMM-Newton X-ray Observatories. This paper also makes use of data obtained as part of the INT Photometric H Survey of the Northern Galactic Plane (IPHAS, www.iphas.org ) carried out at the Isaac Newton Telescope (INT). The INT is operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias. All IPHAS data are processed by the Cambridge Astronomical Survey Unit, at the Institute of Astronomy in Cambridge. The bandmerged DR2 catalog was assembled at the Centre for Astrophysics Research, University of Hertfordshire, supported by STFC grant ST/J001333/1. This publication makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration. This research makes use of the SIMBAD database, operated at CDS, Strasbourg, France. We also make heavy use of R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. ( http://www.R-project.org/ ).
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