Optical spectroscopic observations of gamma-ray blazar candidates. X. Results from the 2018–2019 SOAR and OAN-SPM observations of blazar candidates of uncertain type

Menezes, Raniere de; Amaya-Almazán, Raúl A.; Marchesini, E. J.; Peña-Herazo, H. A.; Massaro, F.; Chavushyan, V.; Paggi, A.; Landoni, M.; Masetti, N.; Ricci, F.; D’Abrusco, R.; Franca, F. La; Smith, H. A.; Milisavljevic, Dan; Tosti, G.; Jiménez‐Bailón, E.; Cheung, C. C.

doi:10.1007/s10509-020-3727-5

Cited by 21 publications

(14 citation statements)

References 51 publications

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“…The completeness plots for our campaign sources with respect to all blazars in the energy range 10 GeV -2 TeV are shown in Figure 3. The latest release of the fourth catalog of AGN detected by the Fermi -LAT (4LAC-DR2; Ajello et al 2020) was used to update the 3FHL catalog in order to include recent redshift measurements and classifications of sources as provided by various campaigns (e.g., Peña-Herazo et al 2017;Paiano et al 2019;de Menezes et al 2020;Paiano et al 2020;Peña-Herazo et al 2020). Completeness was obtained by considering the ratio of the number of classified blazars or blazars with z above a given flux and above divided by the total number of blazars in the same range.…”

Section: Discussionmentioning

confidence: 99%

Identifying the 3FHL catalog: V. Results of the CTIO-COSMOS optical spectroscopy campaign 2019

Rajagopal,

Marchesi,

Kaur

et al. 2021

Preprint

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As a follow-up of 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 uncertain type observed using the 4 m telescope at Cerro Tololo Inter-American Observatory (CTIO) 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, whereas it is observed that the 12 remaining blazars have featureless optical spectra. These results are part of a more extended campaign of optical spectroscopy follow up of 3FHL blazars, where until now 51 blazars of uncertain type have been classified into BL Lac and FSRQ categories. Further, this campaign has resulted in redshift measurements and lower limits for 15 of these sources. Our results contribute towards 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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Section: Discussionmentioning

confidence: 99%

Identifying the 3FHL catalog: V. Results of the CTIO-COSMOS optical spectroscopy campaign 2019

Rajagopal,

Marchesi,

Kaur

et al. 2021

Preprint

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“…The second sample is constituted of 517 blazars observed during our optical spectroscopic campaign (Cowperthwaite et al 2013;Paggi et al 2014;Landoni et al 2015;Massaro et al 2015cRicci et al 2015;Álvarez Crespo et al 2016aÁlvarez Crespo et al , 2016cPeña-Herazo et al 2017Marchesini et al 2019b;de Menezes et al 2020), or collected from the literature (see, e.g., Shaw et al 2013;Paiano et al 2017aPaiano et al , 2017bPaiano et al , 2019Klindt et al 2017;Desai et al 2019). This sample is distinguished in 417 BZBs, 30 BZGs, 44 BZQs, and 24 quasars.…”

Section: Sample Selectionmentioning

confidence: 99%

“…This was the underlying reason to carry out our optical spectroscopic campaign, mainly dedicated to observe target selected on the basis of peculiar mid-IR colors, similar to those of known γ-ray blazars (Massaro et al 2011;D'Abrusco et al 2012D'Abrusco et al , 2019 started in 2014 (Paggi et al 2014;Massaro et al 2015c). Hundreds of new blazars were discovered (Landoni et al 2015;Ricci et al 2015;Álvarez Crespo et al 2016aÁlvarez Crespo et al , 2016cPeña-Herazo et al 2017;Marchesini et al 2019b;Peña-Herazo et al 2019;de Menezes et al 2020), also including searches in the archives of major spectroscopic surveys (Álvarez Crespo et al 2016b;de Menezes et al 2019) as the Sloan Digital Sky Survey (SDSS; Aguado et al 2019), Large Sky Area Multi-Object Fibre Spectroscopic Telescope Data Release 5 (LAMOST DR 5; Zhao et al 2012), and the Six-Degree Field Galaxy Survey (Jones et al 2004(Jones et al , 2009.…”

Section: Introductionmentioning

confidence: 99%

An Optical Overview of Blazars with LAMOST. II. Gamma-Ray Blazar Candidates and Updated Classifications

Peña-Herazo

Massaro

et al. 2021

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Blazars represent the dominant class of associated γ-ray sources detected by the Fermi Large Area Telescope (LAT). However, in the more recent release of the Fourth Fermi-LAT Point Source Catalog (4FGL), ∼25% of the sources associated with lower-energy counterparts show a multifrequency behavior similar to that of blazars, but lacks an optical spectroscopic confirmation of their nature and are therefore classified as Blazar Candidates of Uncertain Type (BCUs). A particularly challenging task in blazar studies is to classify these BCUs and, when possible to estimate their redshifts, in particular for BL Lac objects, characterized by almost featureless optical spectra with only weak emission lines. Continuing our study of blazars with Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) optical spectral data, we perform an extensive search for optical spectra available in the LAMOST Data Release 6 archive. Our aim is confirming the blazar nature of BCUs and to test if new data can allow us to get a redshift estimate for BL Lac objects that lack measurement, as well as to search for and discover changing-look blazars. We selected sources out of the 4FGL catalog, the list of targets from our follow-up spectroscopic campaign of unidentified and/or unassociated γ-ray sources, and the Roma-BZCAT multifrequency catalog of blazars, finding a total of 42 sources with available LAMOST DR6 spectra. We confirmed the blazar-like nature of four blazar candidates . For the remaining 37 sources we confirm their previous classification.

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“…The sources were selected among heterogeneous criteria such as their detection in γ-rays at GeV or TeV band (see e.g. Atwood et al (2009); Paiano et al (2017b), WISE infrared colour (Massaro et al (2012a);D'Abrusco et al (2019);de Menezes et al (2019de Menezes et al ( , 2020) or the properties of their broadband SED (Padovani & Giommi (1995a,b); Costamante & Ghisellini (2002); Costamante (2020)). According to the properties of their optical spectra in ZBLLAC, we labeled 295 objects as BLL by adopting spectral criteria based on the absence of emission features or, if detected, on the value of the EW, luminosities and broadness of the lines.…”

Section: The Zbllac Spectroscopic Databasementioning

confidence: 99%

ZBLLAC -- A spectroscopic database of BL Lacertae objects

Landoni,

Falomo,

Paiano

et al. 2020

Preprint

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This paper describes the database of optical spectra of BL Lacertae (BLL) objects ZBLLAC available at the URL https://web.oapd.inaf.it/zbllac/. At the present date, it contains calibrated spectra for 295 BLL. For about 35% of them, we report a firm measure of redshift z while for 35 sources we set a lower limit on z based on the detection of intervening absorption systems, mainly ascribed to Mg II (λ2800 Å). We report here on the architecture of the database and on its web front-end that permits to filter, query and interactively explore the data. We discuss some properties of the objects in the present dataset by giving the distribution of the redshifts and reporting on the detected emission lines, which turn out to be mainly forbidden and ascribed to [O II] (λ3737 Å) and [O III] (λ5007 Å). Finally, we discuss on intervening absorption systems detected in 35 BLLs that allow us to set lower limits to their distance.

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Optical spectroscopic observations of gamma-ray blazar candidates. X. Results from the 2018–2019 SOAR and OAN-SPM observations of blazar candidates of uncertain type

Cited by 21 publications

References 51 publications

Identifying the 3FHL catalog: V. Results of the CTIO-COSMOS optical spectroscopy campaign 2019

Identifying the 3FHL catalog: V. Results of the CTIO-COSMOS optical spectroscopy campaign 2019

An Optical Overview of Blazars with LAMOST. II. Gamma-Ray Blazar Candidates and Updated Classifications

ZBLLAC -- A spectroscopic database of BL Lacertae objects

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