J/A+A/708/A339 KVN CLEAN images of PKS 1222+216 (Jo+, 2026)
Magnetic field strength constraints on gamma-ray flaring regions in the
flat spectrum radio quasar PKS 1222+216.
Jo Y., Lee S.-S.
<Astron. Astrophys. 708, A339 (2026)>
=2026A&A...708A.339J 2026A&A...708A.339J (SIMBAD/NED BibCode)
ADC_Keywords: QSOs ; Radio sources ; Gamma rays
Keywords: galaxies: active - galaxies: jets - galaxies: magnetic fields -
gamma rays: galaxies - radio continuum: galaxies -
quasars: individual: PKS 1222+216
Abstract:
We present a multi-wavelength study of the Flat Spectrum Radio Quasar
PKS 1222+216, analyzing its long-term variability of radio data
obtained in 2013-2020 from the iMOGABA, MOJAVE, and VLBA-BU-BLAZAR
programs, along with Gamma-ray data from Fermi-LAT. We found that the
radio flux densities at 15, 22, 43, and 86GHz declined exponentially
by 37%-56% over a year following a Gamma-ray flare in November 2014.
We estimated jet physical parameters through Gaussian model fitting of
VLBA 43GHz data, identifying 10 jet components. The cooling timescales
of the jet emission regions, i.e., newly ejected components C9, C10,
and C11, range from 43 to 222 days, with the estimated jet viewing
angles of approximately 8 degrees and magnetic field strengths of
77-134mG in the jet emission regions. Additionally, by determining the
magnetic field strength at different frequencies, we found that the
magnetic field scales as B ∝ r(-0.3±0.04), indicating a
non-equipartition condition (kr≳1) or a slow decline in magnetic
field strength profile (m<1). By analyzing component ejection times,
we discovered that the Gamma-ray flare in 2014 coincided with the
interaction between the moving component C9 and the stationary feature
A1. We estimated that the Gamma-ray emission region is located at
9.2±1.0pc from the core, beyond the BLR and dusty torus, suggesting
that the seed photons for inverse Compton scattering originate from
the jet itself, external CMB radiation, or a surrounding sheath. Our
results favor a scenario where Gamma-ray emission originates further
downstream from the central engine through interactions between moving
and stationary components. Additionally, our study presents an
alternative method for estimating magnetic field strengths in AGNs
undergoing long-term synchrotron cooling based on the associated
timescale.
Description:
This catalogue contains CLEAN images of PKS 1222+216 obtained
with the Korean VLBI Network (KVN) as part of the iMOGABA
monitoring program.
The data presented here cover the period from December 4, 2012
(MJD 56265) to March 6, 2020 (MJD 58914).
CLEAN images of the source were obtained in 54 epochs at
K (22GHz) and Q (43GHz) bands and in 53 epochs at
W (86GHz).
These images correspond to the data used in the analysis
presented in the paper.
Objects:
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RA (2000) DE Designation(s)
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12 24 54.45 +21 22 46.3 PKS 1222+216 = SDSS J122454.46+212246.3
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 142 161 List of fits images
fits/* . 161 Individual fits images
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 23 I4 --- Nx Number of pixels along X-axis
25- 28 I4 --- Ny Number of pixels along Y-axis
30- 39 A10 "datime" Obs.date Observation date
41- 50 E10.5 Hz Freq Observed frequency
52- 55 I4 Kibyte size Size of FITS file
57-101 A45 --- FileName Name of FITS file, in subdirectory fits
103-142 A40 --- Title Title of the FITS file
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Acknowledgements:
Yeji Jo, yejijo(at)khu.ac.kr
License: CC-BY-4.0 [see https://spdx.org/licenses/]
(End) Patricia Vannier [CDS] 10-Mar-2026