Optical spectroscopic observations of gamma-ray blazar candidates III. The 2013/2014 campaign in the Southern Hemisphere

TL;DR

This study uses optical spectroscopy to identify and confirm the blazar nature of gamma-ray sources and their counterparts, expanding understanding of Fermi UGS and related objects in the Southern Hemisphere.

Contribution

First spectroscopic confirmation of optical counterparts of Fermi UGS, revealing their blazar-like nature and providing redshift estimates for high-redshift BL Lac objects.

Findings

Confirmed blazar-like nature for all 6 UGS counterparts

Identified 6 AGUs as BL Lac objects

Discovered high-redshift, luminous BL Lac objects

Abstract

We report the results of our exploratory program carried out with the Southern Astrophysical Research (SOAR) telescope aimed at associating counterparts and establishing the nature of the Fermi Unidentified gamma-ray Sources (UGS). We selected the optical counterparts of 6 UGSs from the Fermi catalog on the basis of our recently discovered tight connection between infrared and gamma-ray emission found for the gamma-ray blazars detected by the Wide-Field Infrared Survey Explorer (WISE) in its the all-sky survey. We perform for the first time a spectroscopic study of the low-energy counterparts of Fermi UGS, in the optical band, confirming the blazar-like nature for the whole sample. We also present new spectroscopic observations of 6 Active Galaxies of Uncertain type associated with Fermi sources (AGUs) that appear to be BL Lac objects. Finally, we report the spectra collected for 6 known gamma-ray blazars belonging to the Roma BZCAT that were obtained to establish their nature or better estimate their redshifts. Two interesting cases of high redshift and extremely luminous BL Lac objects (z>1.18 and z>1.02, based on the detection of Mg II intervening systems) are also discussed.