J/ApJS/278/11 4LAC FSRQs & BL Lac objects energy distributions (Liang+, 2025)
Discerning misclassified flat-spectrum radio quasars from low-frequency-peaked
BL Lacertae objects.
Liang S., Yang W.G., Zheng Y.G., Kang S.J.
<Astrophys. J. Suppl. Ser., 278, 11 (2025)>
=2025ApJS..278...11L 2025ApJS..278...11L
ADC_Keywords: QSOs; BL Lac objects; Gamma rays; Energy distributions; Redshifts
Keywords: Flat-spectrum radio quasars ; BL Lacertae objects
Abstract:
A sample of 312 low-frequency-peaked BL Lacertae objects (LBLs) and
694 flat-spectrum radio quasars (FSRQs) with the parameters of both
redshift and gamma-ray photon spectral index (Γγ) is
compiled from the Fourth Catalog of Active Galactic Nuclei Data
Release 2 from the Fermi Large Area Telescope (LAT). The
multiwavelength data of the sample sources are downloaded from the
Space Science Data Center, and then matched to the corresponding
gamma-ray data from the Fermi-LAT Fourth Source Catalog DR2. The
synchrotron radiation peak frequency and Compton dominance (CD)
parameters of the sources are obtained by using a log-parabolic model
to fit the average-state multiwavelength spectral energy distribution.
A support vector machine in the logLγ-Γγ frame
is utilized to delineate the optimal boundary between FSRQs and LBL
sources. The 1σ position of the Gaussian fitting on the
histograms of the Γγ, logνpeaksyn, and CD
parameter distributions are also introduced. With this criterion,
25 FSRQ candidates are selected from LBL sample sources. The optical
spectral identification result confirms that 8 out of 13 candidate
sources available with the optical spectral data exhibit the
relationship of EW>5Å.
Description:
In this study, we compiled a sample of 694 flat-spectrum radio quasars
(FSRQs) and 312 BL Lacertae objects (LBLs) from the second release of
the Fermi-LAT active galactic nuclei catalog (4LAC-DR2), complemented
by multiband data from the Space Science Data Center (SSDC). Using a
log-parabolic model, we fitted the average-state multiwavelength SEDs
of these sources to derive key physical parameters such as the
effective spectral index, synchrotron peak frequency, and Compton
dominance (CD).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 102 312 Logarithmic parabola fitting results for
BL Lacertae objects (LBLs)
table2.dat 102 694 Logarithmic parabola fitting results for
flat-spectrum radio quasars (FSRQs)
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See also:
VII/248 : Quasars and Active Galactic Nuclei (12th Ed.) (Veron+ 2006)
IX/67 : Fermi LAT 4th source cat. (4FGL-DR3) (Fermi-LAT col., 2022)
J/AJ/87/859 : Polarisation of radio sources at 6 and 20cm (Perley, 1982)
J/A+AS/132/83 : BVRI photometry of 7 BL Lac objects (Bai+ 1998)
J/ApJS/143/1 : FIRST-APM Source Catalog (McMahon+, 2002)
J/ApJ/590/109 : Gamma-ray blazar in northern sky (Sowards-Emmerd+, 2003)
J/ApJS/171/61 : All-Sky Survey of Flat-Spectrum Radio Sources (Healey+, 2007)
J/AJ/135/2453 : Sample of BL Lac objects from SDSS and FIRST (Plotkin+, 2008)
J/MNRAS/396/223 : QSO candidates selection in VO era (D'Abrusco+, 2009)
J/ApJS/180/67 : Phot. selection of quasars from SDSS. II. (Richards+, 2009)
J/ApJ/716/30 : SED of Fermi bright blazars (Abdo+, 2010)
J/ApJ/757/25 : Fermi/LAT AGN at 5GHz (Linford+, 2012)
J/ApJ/757/25 : Fermi/LAT AGN at 5GHz (Linford+, 2012)
J/ApJ/764/135 : Spectroscopic redshifts of BL Lac objects (Shaw+, 2013)
J/ApJS/218/23 : Fermi LAT third source catalog (3FGL) (Acero+, 2015)
J/ApJS/226/20 : X-ray, opt. & radio SEDs of Fermi blazars (Fan+, 2016)
J/other/RAA/18.56 : gamma-ray spectrum for Fermi blazars (Kang+, 2018)
J/ApJS/241/34 : SDSS Reverberation Mapping (SDSS-RM) project (Shen+, 2019)
J/ApJS/247/33 : The Fermi LAT fourth source catalog (4FGL) (Abdollahi+, 2020)
J/ApJ/892/105 : 4th catalog of Fermi LAT-detected AGNs (4LAC) (Ajello+, 2020)
J/ApJS/247/49 : gri obs. of the blazar S5 0716+714 (2017-2019) (Xiong+, 2020)
J/ApJS/253/46 : Optical spectroscopy of Fermi blazars (Paliya+, 2021)
J/ApJS/261/32 : Finding GPQs. II. Sp. obs. of |b|<20° QSOs (Fu+, 2022)
J/ApJS/262/18 : Spectral energy distributions for 4FGL blazars (Yang+, 2022)
J/ApJS/263/24 : The 4LAC-DR3 catalog (Ajello+, 2022)
J/ApJS/265/25 : LAMOST Quasar Survey DR6-DR9 (Jin+, 2023)
http://fermi.gsfc.nasa.gov/ssc/data/access/lat/4LACDR3/ : 4LAC Fermi products
http://www.ssdc.asi.it/ : Space Science Data Center (SSDC) homepage
Byte-by-byte Description of file: table[12].dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- --- [4FGL]
6- 17 A12 --- 4FGL 4FGL name of sources (JHHMM.m+DDd)
19- 42 A24 --- Assoc Associated source name
44- 49 F6.3 --- z [-0.003/4.4]? Redshift (1)
51- 55 F5.3 --- Gamma [1.2/3.3] Gamma-ray photon spectral
index, Γγ
57- 62 F6.3 [Hz] lognupksLP [8.7/26]? Log, Synchrotron radiation
peak frequency; logνpeaksyn
64- 70 F7.3 [Hz] lognupkicLP [8/201.7]? Log, Inverse Compton
scattering peak frequency;
logνpeakic
72- 78 F7.3 [mW/m2] lognufpksynLP [-14/-5.9]? Log, Synchrotron radiation
peak flow; logνfνpeaksyn
80- 86 F7.3 [mW/m2] lognufpkicLP [-20.2/242.5]? Log, Inverse Compton
scattering peak flow;
logνfνpeakic
88- 94 F7.3 --- CD [0/649.6]? Compton dominant parameter
96- 102 F7.4 [10-7W] logLgamma [36.6/50.9]? Log, gamma-ray luminosity
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Note (1): Redshift values were retrieved from the NASA/IPAC
Extragalactic Database (NED). If no redshift measurement was available
in NED, then the value was selected from the 4LAC-DR2 catalog.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 11-Feb-2026