Identifying the 3FHL Catalog. III. Results of the CTIO-COSMOS Optical Spectroscopy Campaign

Abstract

Active galactic Nuclei (AGNs) with their relativistic jets pointed towards the observer, form a subclass of luminous gamma-ray sources commonly known as blazars. The study of blazars is essential to improve our understanding on the AGNs emission mechanisms and evolution, as well as to map the extragalactic background light. To do so, however, one needs to correctly classify and measure a redshift for a large sample of these sources. The Third Fermi-LAT Catalog of High-Energy Sources (3FHL) contains ≈ 1160 blazars reported at energies greater than 10 GeV. However ∼25% of these sources are unclassified and ∼50% lack of redshift information. To increase the spectral completeness of the 3FHL catalog, we are working on an optical spectroscopic follow up campaign using 4-m and 8-m telescopes. In this paper, we present the results of the second part of this campaign, where we observed 23 blazars using the 4 m telescope at CTIO in Chile. We report all the 23 sources to be classified as BL Lacs, a confirmed redshift measurement for 3 sources, a redshift lower limit for 2 sources and a tentative redshift measurement for 3 sources.

Optical spectroscopy of blazars for the Cherenkov Telescope Array

“…After careful examination we possibly detect at the 3.6σ level the CaHK feature at z ∼ 0.421 (the same redshift as in Marchesini et al 2019). We note that at magnitude V = 18.8 the source was much fainter than in Desai et al (2019), which may explain our weak detection and their non-detection. Considering the low significance of the detection, we consider this redshift value as tentative.…”

“…Two spectra of 1RXS J184230.6−584202 have been reported recently. One spectrum (Desai et al 2019) was taken on June 1, 2018, with KOSMOS at the 4 m Mayall telescope. The source had magnitude V = 17.5, and the spectrum was featureless with a S/N of 30.…”

An Empirical “High-confidence” Candidate Zone for Fermi BL Lacertae Objects

“…In addition, we've identified potential BL Lacs and FS-RQs candidates from the 3LAC Clean sample using 4 different SML algorithms (Mclust Gaussian finite mixture models, Decision trees, RF, and SVM; Kang et al 2019a [Paper I]) and from the 4FGL catalogue using 3 different SML algorithms (ANN, RF, and SVM; Kang et al 2019b). Nevertheless, the final confirmation of the BCU nature of candidates in all above approaches is subject to the observations of optical spectroscopy or counterparts in other wavelength (e.g., Massaro et al 2014;Álvarez Crespo et al 2016a,b,c;Massaro et al 2016;Marchesini et al 2016;Klindt et al 2017;Peña-Herazo et al 2017;Marchesi et al 2018;Desai et al 2019;Marchesini et al 2019;Peña-Herazo et al 2019), or broadband spectral features (e.g., Fermi/LAT collaboration, Massaro et al 2009Massaro et al , 2012Massaro et al , 2016Álvarez Crespo et al 2016a,b,c). If such information is missing, classification of BCUs will become challenging especially when no training set is available (see e.g., Shaw et al 2013;Landoni et al 2015;Ricci et al 2015;Paiano et al 2017a,b;Landoni et al 2018;Kaur et al 2019;Kaur et al 2019).…”

Radiografía X del cielo γ

“…A lo largo de nuestra campaña óptico-espectroscópica, aún en curso, para asociar contrapartes a objetos de tipo UGS de Fermi (Paggi et al, 2014a;Massaro et al, 2015b;Landoni et al, 2015b;Ricci et al, 2015;Álvarez Crespo et al, 2016a,b;Peña Herazo et al, 2017;Marchesini et al, 2019a;Peña Herazo et al, 2019), encontramos 27 fuentes que son también parte de nuestra muestra de XBCs. Además, encontramos 23 fuentes más del tipo UGS que fueron clasificadas con espectroscopía óptica en la literatura (Paggi et al, 2014b;Marchesini et al, 2016a;Paiano et al, 2017a;Marchesi et al, 2018;Paiano et al, 2019;Desai et al, 2019). Todas estas 50 fuentes fueron clasificadas en 3 quasares (QSO), 2 BZQ, y 45 BZBs.…”

“…En la columna 1 reportamos el nombre Fermi, en las columnas 2 y 3 las coordenadas ecuatoriales celestes en J2000.0 tomadas del catálogo WISE, en la columna 4 el corrimiento al rojo de la fuente (si fue medido), en la columna 5 la referencia correspondiente en la que fuera publicado su espectro y en la columna 6 el telescopio utilizado para obtener el espectro. Las referencias son: (1) Massaro et al (2014), (2) Paggi et al (2014b), (3) Landoni et al (2015a), (4) , (5) Álvarez Crespo et al (2016c), (6) Paiano et al (2017a), (7) Marchesi et al (2018), (8) Paiano et al (2019), y (9) Desai et al (2019).…”