J/A+A/627/A148 TANAMI radio galaxies I (Angioni+, 2019)
Gamma-ray emission in radio galaxies under the VLBI scope.
I. Parsec-scale jet kinematics and high-energy properties
of gamma-ray-detected TANAMI radio galaxies.
Angioni R. Ros E., Kadler M., Ojha R., Mueller C., Edwards P.G., Burd P.R.,
Carpenter B., Dutka M.S., Gulyaev S., Hase H., Horiuchi S., Krauss F.,
Lovell J.E.J., Natusch T., Phillips C., Ploetz C., Quick J.F.H., Roesch F.,
Schulz R., Stevens J., Tzioumis A.K., Weston S., Wilms J., Zensus J.A.
<Astron. Astrophys. 627, A148 (2019)>
=2019A&A...627A.148A 2019A&A...627A.148A (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei; Galaxies, radio; VLBI
Keywords: galaxies: active - galaxies: nuclei - galaxies: jets -
gamma rays: galaxies
Abstract:
In the framework of the TANAMI multi-wavelength and VLBI monitoring,
we study the evolution of the parsec-scale radio emission in radio
galaxies in the southern hemisphere and their relationship to the
gamma-ray properties of the sources. Our study investigates
systematically, for the first time, the relationship between the two
energy regimes in radio galaxies. In this first paper, we focus on
Fermi-LAT-detected sources. The TANAMI program monitors a large sample
of radio-loud AGN at 8.4GHz and 22.3GHz with the Australian Long
Baseline Array(LBA) and associated telescopes in Antarctica, Chile,
New Zealand and South Africa. We perform a kinematic analysis for five
gamma-ray detected radio galaxies using multi-epoch 8.4 GHz VLBI
images, deriving limits on intrinsic jet parameters such as speed and
viewing angle. We analyzed103 months of Fermi-LAT data in order to
study possible connections between the gamma-ray properties and the
pc-scale jets of Fermi-LAT-detected radio galaxies, both in terms of
variability and average properties. We discuss the individual source
results and draw preliminary conclusions on sample properties
including published VLBI results from the MOJAVE survey, with a total
of fifteen sources. We find that the first gamma-ray detection of
Pictor A might be associated with the passage of a new VLBI component
through the radio core, which appears to be a defining feature of
high-energy emitting Fanaroff-Riley type II radio galaxies. For the
peculiar AGN PKS 0521-36, we detect subluminal parsec-scale jet
motions, and we confirm the presence of fast gamma-ray variability in
the source down to timescales of 6 hours, which is not accompanied by
variations in the VLBI jet. We robustly confirm the presence of
significant superluminal motion, up to βapp∼3, in the jet of
the TeV radio galaxy PKS 0625-35. Our VLBI results constrain the jet
viewing angle to be θ<53°, allowing for the possibility of a
closely aligned jet. Finally, by analyzing the first pc-scale
multi-epoch images of the prototypical Compact Symmetric Object (CSO)
PKS 1718-649, we place an upper limit on the separation speed
between the two mini-lobes, which in turn allows us to derive a lower
limit on the age of the source.Conclusions.We can draw some
preliminary conclusions on the relationship between pc-scale jets and
gamma-ray emission in radio galaxies, basedonFermi-LAT-detected
sources with available multi-epoch VLBI measurements. We find that the
VLBI core flux density correlates with the gamma-ray flux, as seen in
blazars. On the other hand, the gamma-ray luminosity does not show any
dependence on the core brightness temperature and core dominance, two
common indicators of jet Doppler boosting. This seems to indicate that
gamma-ray emission in radio galaxies is not driven by
orientation-dependent effects, as in blazars, which is consistent with
the unified model of jetted AGN.
Description:
VLBI images at 8.4GHz and 22.3GHz of gamma-ray detected radio
galaxies in the TANAMI sample, i.e. Pictor A, PKS 0521-36,
PKS 0625-35, Centaurus B, and PKS 1718-649. The VLBI data has been
calibrated in AIPS and imaged in Difmap following standard procedures.
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------------------
05 19 49.72 -45 46 43.9 PKS 0518-458 = NAME Pictor A
05 22 57.98 -36 27 30.8 PKS 0521-365 = QSO B0521-365
06 27 06.73 -35 29 15.3 PKS 0625-354 = QSO B0625-354
13 46 49.04 -60 24 29.4 PKS 1343-601 = NAME Cen B
17 23 41.03 -65 00 36.6 PKS 1718-649 = NGC 6328
----------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
list.dat 123 36 List of fits images
fits/* . 36 Individual fits images
--------------------------------------------------------------------------------
Byte-by-byte Description of file: list.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
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 "date" Obs.date Observation date
41- 51 E11.6 Hz Freq Observed frequency
53- 57 I5 Kibyte size Size of FITS file
59- 86 A28 --- FileName Name of FITS file, in subdirectory fits
87-123 A37 --- Title Title of the FITS file
--------------------------------------------------------------------------------
Acknowledgements:
Roberto Angioni, angioni(at)mpifr-bonn.mpg.de
(End) Roberto Angioni [MPIfR-Bonn], Patricia Vannier [CDS] 09-Jul-2019