Mon. Not. R. Astron. Soc., 468, 4902-4937 (2017/July-2)
A new method to unveil blazars among multiwavelength counterparts of unassociated Fermi γ-ray sources.
PAIANO S., FRANCESCHINI A. and STAMERRA A.
Abstract (from CDS):
We discuss a new method for unveiling the possible blazar active galactic nucleus nature among the numerous populations of unassociated gamma-ray sources (UGSs) in the Fermi catalogues. Our tool relies on the positional correspondence of the Fermi object with X-ray sources (mostly from Swift-XRT), correlated with other radio, infrared and optical data in the field. We built a set of spectral energy distribution templates representative of the various blazar classes, and we quantitatively compared them to the observed multiwavelength flux density data for all Swift-XRT sources found within the Fermi error box, by taking advantage of some well-recognized regularities in the broad-band spectral properties of the objects. We tested the procedure by comparison with a few well-known blazars, and tested the chance for false-positive recognition of UGSs against known pulsars and other Galactic and extragalactic sources. Based on our spectral recognition tool, we find the blazar candidate counterparts for 14 2FGL UGSs among 183 selected at high galactic latitudes. Furthermore, our tool also allows us to obtain rough estimates of the redshift for the candidate blazar. In a few cases in which this has been possible (i.e. when the counterpart was an SDSS object), we verified that our estimate is consistent with the measured redshift. The estimated redshifts of the proposed UGS counterparts are larger, on average, than those of known Fermiblazars, a fact that might explain the lack of previous association or identification in published catalogues.
© 2017 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society
galaxies: active - gamma-rays: galaxies - BL Lacertae objects: general - BL Lacertae objects: general
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