J/MNRAS/510/469 Radio and Γ-ray of MOJAVE-Fermi AGNs (Kramarenko+, 2022)
A decade of joint MOJAVE-Fermi AGN monitoring localization of the gamma-ray
emission region.
Kramarenko I.G., Pushkarev A.B., Kovalev Y.Y., Lister M.L., Hovatta T.,
Savolainen T.
<Mon. Not. R. Astron. Soc. 510, 469-480 (2022)>
=2022MNRAS.510..469K 2022MNRAS.510..469K (SIMBAD/NED BibCode)
ADC_Keywords: QSOs ; Active gal. nuclei ; BL Lac objects ; Galaxies, radio ;
Galaxies, Seyfert ; Gamma rays ; Radio sources ; Optical ;
Photometry ; Spectroscopy ; Photometry, classification ; Redshifts
Keywords: galaxies: active - galaxies: jets - galaxies: nuclei -
gamma-rays: galaxies - radio continuum: galaxies
Abstract:
Within the MOJAVE VLBA programme (Monitoring of Jets in AGN with VLBA
Experiments), we have accumulated observational data at 15 GHz for
hundreds of jets in gamma-ray bright active galactic nuclei since the
beginning of the Fermi scientific observations in 2008 August. We
investigated a time delay between the flux density of AGN parsec-scale
radio emission at 15 GHz and 0.1-300 GeV Fermi LAT photon flux, taken
from constructed light curves using weekly and adaptive binning. The
correlation analysis shows that radio is lagging gamma-ray radiation
by up to 8 months in the observer's frame, while in the source frame,
the typical delay is about 2-3 months. If the jet radio emission,
excluding the opaque core, is considered, significant correlation is
found at greater time lags. We supplement these results with VLBI
kinematics and core shift data to conclude that the dominant
high-energy production zone is typically located at a distance of
several parsecs from the central nucleus. We also found that quasars
have on average more significant correlation peak, more distant
gamma-ray emission region from the central engine and shorter
variability time-scale compared to those of BL Lacertae objects.
Description:
The question of the dominant production mechanism and the exact
location of the gamma-ray emission observed in active galactic nuclei
(AGNs) remains unresolved for several decades. The lack of
high-resolution instruments and the complex nature of AGNs have
resulted in numerous hypotheses about the origin of the gamma-ray
photons. One of the most frequently given explanations of the observed
gamma-ray emission from AGNs is the inverse Compton scattering of soft
photons by the jet relativistic electrons.
Fermi has accumulated more than 10 yr of observational data of more
than 3000 gamma-ray bright blazars, providing great possibilities for
studying the gamma-ray emission observed in AGNs. In this study, we
perform a cross-correlation analysis between the up-to-date Fermi/LAT
gamma-ray flux and MOJAVE radio flux densities related to various VLBA
components to address the following questions: (i) whether the
gamma-ray photons pre-dominantly originate upstream of the 15 GHz VLBA
core, (ii) whether the gamma-ray emission zone is located within the
BLR (≲0.1 pc) or beyond it at greater scales downstream the jet,
(introduction section).
Our sample consists of 331 MOJAVE AGNs which have positionally
associated (100 MeV-300 GeV) gamma-ray bright Fermi blazars
counterparts from the Fermi LAT Fourth Source Catalog (4FGL-DR2, see
section 3.2 Gamma-ray data Abdollahi et al. 2020ApJS..247...33A 2020ApJS..247...33A, Cat.
J/ApJS/247/33). We do not consider a source if there are less than
five radio epochs available or the galactic latitude |b| < 10 deg (we
checked that this cut-off does not affect the results of our study).
The sample includes 198 objects that are a part of a complete set of
232 sources whose 15 GHz VLBA correlated flux density exceeds 1.5 Jy
at any epoch between 1994.0 and 2019.0 (Lister et al.
2019ApJ...874...43L 2019ApJ...874...43L, Cat. J/ApJ/874/43). The AGNs included in the
current analysis are listed in table1.dat which contains optical
classes, redshifts z, and median apparent jet speeds Βapp for
sources are taken from Lister et al. (2021ApJ...923...30L 2021ApJ...923...30L, Cat.
J/ApJ/923/30, source structure modelfits containing the core and jet
feature flux densities). In total, there are 194 quasars, 112 BL Lacs,
13 radio galaxies, six narrow-line Seyfert 1 galaxies and six sources
with unknown spectral class in the sample. The redshifts are known for
281 (85 per cent) AGNs, with a median of 0.79. For a given source,
Βapp is estimated as a maximum of the apparent speeds over all
VLBA components. The apparent speeds obtained in that way are known
for 261 (79 per cent) AGNs and have a median of ∼8.7 c, (Source sample
section 2).
Radio data section 3, in our study, we used data of 4275 observations
of 331 active galactic nuclei constituting our sample obtained with
the VLBA at 15 GHz between 2005 January 6 and 2019 August 4 at 376
unique epochsThe radio flux densities of individual components were
derived at each observing epoch by fitting a source brightness
distribution with a limited number of circular or elliptical Gaussian
components. The uncertainties of the VLBA 15 GHz flux densities are
estimated to be about 5 per cent, (see also the section 4 for ZDCF
correlation analysis, section 5 Radio/Gamma time delay and section 6
Γ-ray emission localization).
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 50 331 Our sample of 331 bright blazars AGNs
lc/* . 331 The individual light curves in pdf format
(with file names BName4FGL4FGLNlc.pdf)
--------------------------------------------------------------------------------
See also:
J/ApJS/247/33 : The Fermi LAT fourth source catalog (4FGL) (Abdollahi+, 2020)
IX/67 : Incremental Fermi LAT 4th source cat. (4FGL-DR3)
(Fermi-LAT col., 2022)
J/ApJS/234/12 : MOJAVE XV. VLBA 15GHz obs. of AGN jets 1996-2016 (Lister+,2018)
J/ApJ/874/43 : MOJAVE. XVII. Parsec-scale jet kinematics of AGNs
(Lister+, 2019)
J/ApJ/923/30 : MOJAVE. XVIII. Bright radio-loud active AGNs (Lister+, 2021)
http://heasarc.gsfc.nasa.gov/FTP/fermi/data/lat/weekly/diffuse : Fermi LAT data
https://fermi.gsfc.nasa.gov/ssc/data/analysis/documentation/ : NASA Fermi LAT
https://www.cv.nrao.edu/MOJAVE/ : Mojave program & data maps home page
https://github.com/hey-moon/ZDCF : ZDCF python 3 code
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- BName Source (HHMM+DDd; B1950) as in MOJAVE XVIII
Lister et al. 2021ApJ...923...30L 2021ApJ...923...30L
Cat. J/ApJ/923/30 (Source)
10- 21 A12 --- 4FGLN The 4FGL name (JHHMM.m+DDMM[c/e/i/s]) as in 4FGL
Abdollahi et al. 2022ApJS..260...53A 2022ApJS..260...53A
Cat. IX/67 (FermiName)
23- 25 I3 --- Nrad Number of radio observation epochs from MOJAVE
XVIII Lister et al. 2021ApJ...923...30L 2021ApJ...923...30L
Cat. J/ApJ/923/30 (N)
27 A1 --- Class Optical classification from MOJAVE XVIII
Lister et al. 2021ApJ...923...30L 2021ApJ...923...30L
Cat. J/ApJ/923/30 (Opt) (1)
29- 34 F6.4 --- z ? Spectroscopic redshift from MOJAVE XVIII
Lister et al. 2021ApJ...923...30L 2021ApJ...923...30L
Cat. J/ApJ/923/30 (z)
36- 42 F7.4 c beta ? Maximum apparent jet speed in unit of c from
MOJAVE XVIII Lister et al. 2021ApJ...923...30L 2021ApJ...923...30L
Cat. J/ApJ/923/30 (Βapp)
44- 50 F7.4 c e_beta ? Uncertainty in apparent jet speed Βapp
(errΒapp)
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Note (1): Optical visual classification as follows:
Q = Quasar
B = BL Lac
G = Radio galaxy,
N = Narrow-line Seyfert 1
U = Unknown spectral class
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History:
From electronic version of the journal
(End) Luc Trabelsi [CDS] 17-Oct-2024