Swift detection of all previously undetected blazars in a micro-wave flux-limited sample of WMAP foreground sources

Abstract

Almost the totality of the bright foreground sources in the WMAP CMB maps are blazars, a class of sources that show usually also X-ray emission. However, 23 objects in a flux-limited sample of 140 blazars of the WMAP catalog (first year) were never reported before as X-ray sources. We present here the results of 41 Swift observations which led to the detection of all these 23 blazars in the 0.3-10 keV band. We conclude that all micro-wave selected blazars are X-ray emitters and that the distribution of the micro-wave to X-ray spectral slope ${\alpha }_{mux}$ of LBL blazars is very narrow, confirming that the X-ray flux of most blazars is a very good estimator of their micro-wave emission. The X-ray spectral shape of all the objects that were observed long enough to allow spectral analysis is flat and consistent with inverse Compton emission within the commonly accepted view where the radiation from blazars is emitted in a Sychrotron-Inverse-Compton scenario. We predict that all blazars and most radio galaxies above the sensitivity limit of the WMAP and of the Planck CMB missions are X-ray sources detectable by the present generation of X-ray satellites. An hypothetical all-sky soft X-ray survey with sensitivity of approximately $10^{-15}$ erg/s would be crucial to locate and remove over 100,000 blazars from CMB temperature and polarization maps and therefore accurately clean the primordial CMB signal from the largest population of extragalactic foreground contaminants.

arXiv comment13 pages, 4 figures, 5 tables, A&A in press

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• A simplified view of blazars: clearing the fog around long-standing selection effects
• The Wilkinson Microwave Anisotropy Probe (WMAP) Source Catalog
• Testing the blazar spectral sequence: X-ray selected blazars
• The low-frequency radio catalog of flat spectrum sources
• The Impact of the Environment on the Early Stages of Radio Source Evolution
• First detection of hard X-ray photons in the soft X-ray transient Narrow-Line Seyfert 1 galaxy WPVS 007: The X-ray photon distribution observed by Swift
• Identification of New Gamma-Ray Blazar Candidates With Multifrequency Archival Observations
• The number counts, luminosity functions and evolution of microwave-selected (WMAP) blazars and radio galaxies