Optical Spectroscopic Observations of Gamma-Ray Blazar Candidates. VII.
  Follow-up Campaign in the Southern Hemisphere
  Searching for low energy counterparts of gamma-ray sources is one of the
major challenges in modern gamma-ray astronomy. In the third Fermi source
catalog about 30 % of detected sources are unidentified/unassociated Gamma-ray
Sources (UGSs). We recently started an optical spectroscopic follow up campaign
to confirm the blazar-like nature of candidates counterparts of UGSs. Here we
report the spectra of 61 targets collected with the Southern Astrophysical
Research Telescope (SOAR) between 2014 and the 2017. Our sample includes 33
potential counterparts of UGSs, selected on the basis of WISE colors, and 27
blazar candidates of uncertain type associated with gamma-ray sources of the
last release of the Fermi catalog. We confirm the BZB nature of 20 sources
lying within the positional uncertainty region of the UGSs. All the observed
BCUs show blazar-like spectra, classified as 2 BZQs and 25 BZBs, for which we
obtained 6 redshift estimates. Within the BCUs observations we report the
redshift estimate for the BZB associated with, 3FGL J1106.4-3643 that is the
second most distant BL Lac known to date, at z>1.084.
