Optical spectroscopic classification of a selection of Southern Hemisphere Fermi-LAT unclassified blazars

Abstract

The Fermi-LAT has detected more than 3000 sources in the GeV $\gamma$-ray regime. The majority are extra-galactic and these sources are dominated by blazars. However, $\sim 28$ per cent of the sources in Fermi 3LAC are listed as blazar candidates of uncertain type (BCU). Increasing the number of classified Fermi-LAT sources is important for improving our understanding of extra-galactic $\gamma$-ray sources and can be used to search for new very high energy sources. We report on the optical spectroscopy of seven selected unclassified BCU sources during 2014 and 2015 undertaken using the SAAO 1.9-m and Southern African Large Telescope (SALT). Based on the identified spectral lines we have classified three of the sources as FSRQs and the remaining four as BL Lac objects, determining the redshift for four sources.

arXiv comment9 page, 10 figures, 5 tables. Accepted for publication in MNRAS

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• Fundamental differences in the properties of red and blue quasars: measuring the reddening and accretion properties with X-shooter
• Optical spectroscopic characterization of Fermi blazar candidates of uncertain type with TNG and DOT: First Results
• An empirical "high-confidence" candidate zone for $Fermi$ BL Lacertae objects