J/AJ/161/196 An optical overview of blazars with LAMOST. I. (Pena-herazo+, 2021)
An optical overview of blazars with LAMOST.
I. Hunting changing-look blazars and new redshift estimates.
Pena-herazo H.A., Massaro F., Gu M., Paggi A., Landoni M., D'abrusco R.,
Ricci F., Masetti N., Chavushyan V.
<Astron. J., 161, 196-196 (2021)>
=2021AJ....161..196P 2021AJ....161..196P (SIMBAD/NED BibCode)
ADC_Keywords: BL Lac objects; QSOs; Active gal. nuclei; Redshifts; Optical
Keywords: Optical identification; Blazars; BL Lacertae objects
Flat-spectrum radio quasars
Abstract:
The extragalactic γ-rays sky observed by the Fermi Large Area
Telescope (LAT) is dominated by blazars. In the fourth release of the
Fermi LAT Point Source Catalog (4FGL) are sources showing a
multifrequency behavior similar to that of blazars but lacking an
optical spectroscopic confirmation of their nature, known as blazar
candidates of uncertain type (BCUs). We aim at confirming the blazar
nature of BCUs and test if new optical spectroscopic observations can
reveal spectral features, allowing us to get a redshift estimate for
known BL Lac objects. We also aim to search for and discover
changing-look blazars (i.e., blazars that show a different
classification at different epochs). We carry out an extensive search
for optical spectra available in the Large Sky Area Multi-object Fibre
Spectroscopic Telescope (LAMOST) Data Release 5 (DR5) archive. We
select sources out of the 4FGL catalog, the list of targets from our
follow-up spectroscopic campaign of unidentified or unassociated
γ-ray sources, and the multifrequency catalog of blazars: the
Roma-BZCAT. We select a total of 392 spectra. We also compare some of
the LAMOST spectra with those available in the literature. We classify
20 BCUs confirming their blazar-like nature. Then we obtain 15 new
redshift estimates for known blazars. We discover 26 transitional
(i.e., changing-look) blazars that changed their classification.
Finally, we are able to confirm the blazar-like nature of six BL Lac
candidates. All remaining sources analyzed agree with previous
classifications. BL Lac objects are certainly the most elusive type of
blazars in the γ-ray extragalactic sky.
Description:
We extracted sources to carry out our analysis from the following
three samples or catalogs:
(1) The first catalog is the 4FGL (Abdollahi+, 2020, J/ApJS/247/33)
based on the first eight years of science data collected by Fermi in
the energy range between 50MeV and 1TeV.
(2) We selected the 517 sources listed in our optical follow-up
campaign to unveil the nature of unidentified/unassociated γ-ray
sources (UGSs) and blazar candidates of uncertain type (BCUs).
(3) Finally, we also verify redshifts and classification of those
blazars listed in the Roma-BZCAT v5.0
For all sources in our three samples, we retrieved the optical
spectrum available in the LAMOST DR5 and performed the spectral
analysis to measure emission or absorption lines eventually
detectable.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 77 392 Classification results
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See also:
IX/32 : ROSAT Bright Survey (Fischer+, 1998-2000)
VII/259 : 6dF galaxy survey final redshift release (Jones+, 2009)
VII/274 : The Roma BZCAT - 5th edition (Massaro+, 2015)
V/164 : LAMOST DR5 catalogs (Luo+, 2019)
J/ApJ/707/L56 : VLBI and bright Fermi/LAT sources (Kovalev, 2009)
J/ApJ/715/429 : First Fermi-LAT AGN catalog (1LAC) (Abdo+, 2010)
J/ApJ/716/30 : SED of Fermi bright blazars (Abdo+, 2010)
J/ApJS/188/405 : Fermi-LAT first source catalog (1FGL) (Abdo+, 2010)
J/ApJ/748/49 : Optical spectroscopy of 1LAC broad-line blazars (Shaw+, 2012)
J/ApJ/748/68 : WISE IR colors of gamma-ray blazars (D'Abrusco+, 2012)
J/ApJ/752/61 : Blazars in unidentified gamma-ray sources (Massaro+, 2012)
J/ApJ/753/83 : Associations to 1FGL sources (Ackermann+, 2012)
J/ApJ/756/33 : X-ray sources near 2 bright gamma-ray sources (Cheung+, 2012)
J/ApJS/199/31 : Fermi LAT second source catalog (2FGL) (Nolan+, 2012)
J/ApJS/201/10 : SDSS quasar catalog with Swift observations (Wu+, 2012)
J/AJ/146/120 : MOJAVE. X. Parsec-scale kinematics of AGNs (Lister+, 2013)
J/ApJ/763/L36 : MgII and FeII flux of the blazar 3C454.3 (Leon-Tavares+, 2013)
J/ApJ/764/135 : Spectroscopic redshifts of BL Lac objects (Shaw+, 2013)
J/ApJ/779/133 : X-ray & radio fluxes unassociated 2FGL sources (Acero+, 2013)
J/ApJS/206/12 : Blazars with gamma-ray counterparts. I. (D'Abrusco+, 2013)
J/ApJS/206/13 : Blazars with gamma-ray counterparts. II. (Massaro+, 2013)
J/ApJS/207/4 : Unidentified gamma-ray sources. III. Radio (Massaro+, 2013)
J/ApJS/207/16 : BL Lac candidates for TeV observations (Massaro+, 2013)
J/ApJS/208/25 : Swift X-ray observations of 1FGL sources (Takeuchi+, 2013)
J/ApJS/209/9 : Unidentified gamma-ray sources. IV. X-ray (Paggi+, 2013)
J/ApJS/209/10 : UGSs. V. kernel approach (Massaro+, 2013)
J/MNRAS/432/1294 : Fermi unassociated sources ATCA observations (Petrov+, 2013)
J/ApJ/780/73 : Redshifts of BL Lac objects from Fermi (Ajello+, 2014)
J/ApJ/782/41 : 231 AGN candidates from the 2FGL catalog (Doert+, 2014)
J/ApJS/215/14 : WISE cand. gamma-ray blazar radio sources (D'Abrusco+, 2014)
J/A+A/579/A34 : 1WHSP: VHE gamma-ray blazar candidates (Arsioli+, 2015)
J/ApJ/810/14 : Third catalog of LAT-detected AGNs (3LAC) (Ackermann+, 2015)
J/ApJS/217/2 : Refined associations of Fermi/LAT sources (Massaro+, 2015)
J/ApJS/217/4 : 2FGL sources observed between 5-9GHz (Schinzel+, 2015)
J/ApJS/218/23 : Fermi LAT third source catalog (3FGL) (Acero+, 2015)
J/A+A/588/A141 : The MWA view of Fermi blazars (Giroletti+, 2016)
J/ApJS/222/5 : The second Fermi-LAT >50GeV catalog (2FHL) (Ackermann+, 2016)
J/ApJS/224/26 : Spectral energy distributions Roma BZCAT blazars (Mao+, 2016)
J/ApJS/226/20 : X-ray, opt. & radio SEDs of Fermi blazars (Fan+, 2016)
J/ApJ/838/139 : Radio follow-up on 3FGL unassociated sources (Schinzel+, 2017)
J/MNRAS/470/1291 : Classifying 3FGL with ANN (Salvetti+, 2017)
J/ApJ/861/130 : BL Lac objects GTC low resolution spectroscopy (Landoni+,2018)
J/A+A/631/A150 : Softly X-raying the gamma-ray sky I. (Marchesini+, 2019)
J/ApJ/887/18 : Classific. of X-ray counterparts of 3FGL sources (Kaur+, 2019)
J/ApJS/242/4 : Two new catalogs of blazar candidates (D'Abrusco+, 2019)
J/A+A/643/A103 : Fermi-LATi sources low-energy counterparts (Pena-Herazo+,2020)
J/ApJS/247/33 : The Fermi LAT fourth source catalog (4FGL) (Abdollahi+, 2020)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Cat Original sample catalog (1)
9- 27 A19 --- Name Source name
29- 32 A4 --- Class1 Class in the sample catalog (2)
34- 41 F8.6 --- z1 [0.01/3.41]? Redshift in the sample catalog
43- 61 A19 --- LAMOST LAMOST designated name
63- 65 A3 --- Class2 Class identified thanks to our analysis (2)
67- 71 F5.3 --- z2 [0.01/3.43]? Redshift measurement thanks to our
analysis
73- 77 A5 --- SDSSspec? True/false flag indicating an available SDSS
spectrum (204 false, 188 true)
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Note (1): Sample catalogs as follows:
4FGL = Fermi Large Aera Telescope Point Source Catalog DR4 (31 occurrences)
BZCAT = Roma-BZCAT 5th edition (353 occurrences)
OptCamp = Optical campaign (8 occurrences)
Note (2): Class as follows:
agn = Active Galactic Nuclei
bcu = Blazar Candidates of Uncertain type
bll = BL Lac objects
bzb = Blazar with CaII break <0.25
bzg = Blazar with CaII break ≥0.25
bzq = Latter subclass Blazar
fsrq = Flat-Spectrum Radio Quasars
sey = Seyfert 2-like spectrum
rg = radio galaxy
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 29-Jun-2021