J/ApJ/951/133 Spectral energy distributions of Fermi blazars (Kerby+, 2023)
Testing the blazar sequence with spectra of recently discovered dim blazars from
the Fermi unassociated catalog.
Kerby S., Falcone A.D.
<Astrophys. J., 951, 133 (2023)>
=2023ApJ...951..133K 2023ApJ...951..133K
ADC_Keywords: BL Lac objects; Active gal. nuclei; Gamma rays; X-ray sources;
Radio sources; Energy distributions
Keywords: Blazars ; Catalogs
Abstract:
Recent works have developed samples of blazars from among the Fermi
Large Area Telescope unassociated sources via machine-learning
comparisons with known blazar samples. Continued analysis of these new
blazars tests the predictions of the blazar sequence and enables more
flux-complete samples of blazars as a population. Using Fermi, Swift,
Wide-field Infrared Survey Explorer, and archival radio data, we
construct broadband spectral energy distributions for 106 recently
identified blazars. Drawn from the unassociated 4FGL source sample,
this new sample has a lower median flux than the overall sample of
gamma-ray blazars. By measuring the synchrotron peak frequency, we
compare our sample of new blazars with known blazars from the 4LAC
catalog. We find that the bulk of the new blazars are similar to
high-synchrotron-peaked BL Lac objects, with a higher median
synchrotron peak; the sample has a median log(νsyn/Hz)=15.5 via
BLaST peak estimation, compared to log(νsyn/Hz)=14.2 for the 4LAC
BL Lacs. Finally, we conduct synchrotron self-Compton leptonic
modeling, comparing fitted physical and phenomenological properties to
brighter blazars. We find that the new blazars have smaller
characteristic Lorentz factors γboost and fitted magnetic fields
B, in agreement with blazar sequence predictions. The new blazars have
slightly higher Compton dominance ratios than expected, which may
point to alternative emission models for these dim blazars. Our
results extend the predictions of the blazar sequence to a sample of
dimmer blazars, confirming the broad predictions of that theory.
Description:
The 106 blazars in Kaur+ 2023, J/ApJ/943/167 are the foundation of the
sample used in this work.
Building off the Fermi-LAT fluxes (IX/67), we incorporate the
Swift-XRT data used in Kerby+ 2021, J/ApJ/923/75 and
Kaur+ 2023, J/ApJ/943/167 into each spectrum.
Finally, we conduct a position cross-match between the XRT centroids
of the likely blazars with the SUMSS (Mauch+ 2003, VIII/81), NVSS
(Condon+ 1998, VIII/65), and VLASS (Gordon+ 2021, J/ApJS/255/30) radio
surveys.
Combining the gamma-ray through radio fluxes, we produce a SED for
each source such as that shown in Figure 2.
See Section 2.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 81 106 *Phenomological features of the broadband spectral
energy distributions (SEDs) from agnpy fitting
unless otherwise noted
table3.dat 94 106 *Synchrotron-self-Compton fits via agnpy with
fixed z=0.34
fig2/* . 106 Individual SED data in ecsv FORMAT
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Note on table2.dat and table3.dat: We conduct Synchrotron Self-Compton (SSC)
modeling of our SEDs using the agnpy modeling package
(Nigro+ 2022A&A...660A..18N 2022A&A...660A..18N); see Section 3.2.
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See also:
VIII/65 : 1.4GHz NRAO VLA Sky Survey (NVSS) (Condon+ 1998)
VIII/78 : Sydney University Molonglo Sky Survey (SUMSS) (Mauch+ 2006)
VIII/81 : Sydney University Molonglo Sky Survey (SUMSS V2.1) (Mauch+ 2008)
IX/67 : Fermi LAT 4th source cat. (4FGL-DR3) (Fermi-LAT col., 2022)
J/ApJ/722/520 : Gamma-ray light curves of Fermi blazars (Abdo+, 2010)
J/ApJ/716/30 : SED of Fermi bright blazars (Abdo+, 2010)
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/ApJ/923/75 : X-ray/UV/opt counterparts of 4FGL sources (Kerby+, 2021)
J/ApJS/255/30 : VLASS QL Ep.1 Catalog, CIRADA version (Gordon+, 2021)
J/ApJS/263/24 : The 4LAC-DR3 catalog (Ajello+, 2022)
J/ApJ/943/167 : FSRQs & BL Lac objects from 4FGL blazar cand. (Kaur+, 2023)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 12 A12 --- 4FGL Fermi-LAT 4FGL DR3 position-based
identifier
14- 30 A17 --- XRT Swift-XRT position-based identifier
32- 37 F6.3 [Hz] lognuBLaST [12.2/17.3] Log, synchrotron peak
frequency, from BLaST
(log(νsyn,BLaST)) (1)
39- 43 F5.3 [Hz] e_lognuBLaST [0.4/2.4] lognuBLaST uncertainty
(log(δνsyn,BLaST)) (1)
45- 50 F6.3 [Hz] lognusyn [12.8/18.3] Log, synchrotron peak
frequency (log(ν_syn))
52- 58 F7.3 [mW/m2] lognuFnusyn [-13.7/-9.8] Log, synchrotron peak flux,
erg/s/cm2
60- 65 F6.3 [Hz] lognuCom [20.9/25.9] Log, high-energy peak
frequency
67- 73 F7.3 [mW/m2] lognuFnuCom [-13.3/-11] Log, high-energy peak flux,
erg/s/cm2
75- 81 F7.3 [mW/m2] logFbol [-10.5/-8] Log, bolometric flux, erg/s/cm2
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Note (1): BLaST (Glauch+ 2022A&C....4100646G 2022A&C....4100646G) uses machine learning trained
on almost 4000 known blazar SEDs to predict the positions of the
synchrotron peak frequency, being especially resilient against
misreading processes like dust or disk emission as jet synchrotron
emission. See Section 3.1.
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 12 A12 --- 4FGL Fermi-LAT 4FGL DR3 position-based identifier
14- 30 A17 --- XRT Swift-XRT position-based identifier
32- 37 F6.3 [-] logke [-8.9/-0.26] agnpy synchrotron self-Compton
(SSC) parameter, scaling factor
39- 44 F6.3 --- p1 [-1.8/4] agnpy SSC parameter, power-law
index below break
46- 50 F5.3 --- p2 [1.3/8] agnpy SSC parameter, power-law index
above break
52- 56 F5.3 [-] loggam [2/5.6] agnpy SSC parameter, break Lorentz
factor
58- 62 F5.3 [-] loggamMax [5/8] agnpy SSC parameter, minimum electron
factor
64- 68 F5.3 [-] loggamMin [1/4] agnpy SSC parameter, maximum electron
factor
70- 75 F6.3 --- dD [4/41.2] agnpy SSC parameter, Doppler
factor, δD
77- 82 F6.3 [G] logB [-2/0.2] agnpy SSC parameter, magnetic field
strength
84- 88 F5.3 [s] logtvar [4/6.1] agnpy SSC parameter, variability
timescale
90- 94 F5.3 --- chi2r [0.28/4] Reduced χ2 of fit
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 21-Aug-2025