Data di Pubblicazione:
2015
Abstract:
The Fermi-Large Area Telescope (LAT) First Source Catalog (1FGL) was released in 2010 February and the
Fermi-LAT 2-Year Source Catalog (2FGL) appeared in 2012 April, based on data from 24 months of operation.
Since they were released, many follow up observations of unidentified γ-ray sources have been performed and new
procedures for associating γ-ray sources with potential counterparts at other wavelengths have been developed.
Here we review and characterize all of the associations as published in the 1FGL and 2FGL catalogs on the basis of
multifrequency archival observations. In particular, we located 177 spectra for the low-energy counterparts that
were not listed in the previous Fermi catalogs, and in addition we present new spectroscopic observations of eight
γ-ray blazar candidates. Based on our investigations, we introduce a new counterpart category of “candidate
associations” and propose a refined classification for the candidate low-energy counterparts of the Fermi sources.
We compare the 1FGL-assigned counterparts with those listed in 2FGL to determine which unassociated sources
became associated in later releases of the Fermi catalogs. We also search for potential counterparts to all of the
remaining unassociated Fermi sources. Finally, we prepare a refined and merged list of all of the associations of
1FGL plus 2FGL that includes 2219 unique Fermi objects. This is the most comprehensive and systematic study of
all the associations collected for the γ-ray sources available to date. We conclude that 80% of the Fermi sources
have at least one known plausible γ-ray emitter within their positional uncertainty regions.
Tipologia CRIS:
03A-Articolo su Rivista
Keywords:
galaxies: active , methods: statistical , quasars: general , surveys
Elenco autori:
F. Massaro;R. D’Abrusco;M. Landoni;A. Paggi;N. Masetti;M. Giroletti;H. Otí-Floranes;V. Chavushyan;E. Jiménez-Bailón;V. Patiño-Álvarez;S. W. Digel;Howard A. Smith;G. Tosti
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