TY - JOUR
T1 - Identifying the 3FHL Catalog. V. Results of the CTIO-COSMOS optical spectroscopy campaign 2019
AU - Rajagopal, M.
AU - Marchesi, S.
AU - Kaur, A.
AU - Domínguez, A.
AU - Silver, R.
AU - Ajello, M.
N1 - Funding Information:
which the universe becomes opaque to gamma-rays (τγγ= 1, where τγγ is the optical depth of EBL as estimated from the models). This opacity originates when very high-energy (E > 100 GeV) photons interact with the low-energy EBL photons causing electron–positron pair production to occur, thus annihilating the photons in the process (Domínguez et al. 2013). The CGRH as a function of redshift has been plotted in Figure 3 for all the highest-energy photons (HEP) in the 3FHL catalog (Ajello et al. 2017). We highlight in the figure both the objects studied in our spectroscopic campaign and the photometric campaign. The photometric dropout technique is based on the flux attenuation caused by the interaction of M.R., S.M., and M.A. acknowledge support from NASA contract 80NSSC19K0151. A.D. is thankful for the support of the Ramón y Cajal program from the Spanish MINECO. The authors thank Alberto Alvarez, Claudio Aguilera, and Sean Points for the help provided during the observing nights at CTIO. This work made use of the TOPCAT software for the analysis of data tables.
Publisher Copyright:
© 2021. The American Astronomical Society. All rights reserved.
PY - 2021/6
Y1 - 2021/6
N2 - As a follow-up to the optical spectroscopic campaign aimed at achieving completeness in the Third Catalog of Hard Fermi-LAT Sources (3FHL), we present here the results of a sample of 28 blazars of an uncertain type observed using the 4 m telescope at Cerro Tololo Inter-American Observatory in Chile. Out of these 28 sources, we find that 25 are BL Lacertae objects (BL Lacs) and 3 are flat-spectrum radio quasars (FSRQs). We measure redshifts or lower limits for 16 of these blazars, and it is observed that the 12 remaining blazars have featureless optical spectra. These results are part of a more extended optical spectroscopy follow-up campaign for 3FHL blazars, where, until now, 51 blazars of an uncertain type have been classified into BL Lac and FSRQ categories. Furthermore, this campaign has resulted in redshift measurements and lower limits for 15 of these sources. Our results contribute toward attaining a complete sample of blazars above 10 GeV, which then will be crucial in extending our knowledge on blazar emission mechanisms and the extragalactic background light.
AB - As a follow-up to the optical spectroscopic campaign aimed at achieving completeness in the Third Catalog of Hard Fermi-LAT Sources (3FHL), we present here the results of a sample of 28 blazars of an uncertain type observed using the 4 m telescope at Cerro Tololo Inter-American Observatory in Chile. Out of these 28 sources, we find that 25 are BL Lacertae objects (BL Lacs) and 3 are flat-spectrum radio quasars (FSRQs). We measure redshifts or lower limits for 16 of these blazars, and it is observed that the 12 remaining blazars have featureless optical spectra. These results are part of a more extended optical spectroscopy follow-up campaign for 3FHL blazars, where, until now, 51 blazars of an uncertain type have been classified into BL Lac and FSRQ categories. Furthermore, this campaign has resulted in redshift measurements and lower limits for 15 of these sources. Our results contribute toward attaining a complete sample of blazars above 10 GeV, which then will be crucial in extending our knowledge on blazar emission mechanisms and the extragalactic background light.
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U2 - 10.3847/1538-4365/abf656
DO - 10.3847/1538-4365/abf656
M3 - Article
AN - SCOPUS:85106660119
SN - 0067-0049
VL - 254
JO - Astrophysical Journal, Supplement Series
JF - Astrophysical Journal, Supplement Series
IS - 2
M1 - 29
ER -