J/A+A/672/A104 Jets in FR0 radio galaxies (Giovannini+, 2023)
Jets in FR0 radio galaxies.
Giovannini G., Baldi R.D., Capetti A., Giroletti M., Lico R.
<Astron. Astrophys. 672, A104 (2023)>
=2023A&A...672A.104G 2023A&A...672A.104G (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; Radio sources ; Radio continuum
Keywords: radio continuum: galaxies - galaxies: active - galaxies: jets
Abstract:
The local radio-loud AGN population is dominated by compact sources
named FR0s. These sources show features, for example the host type,
the mass of the supermassive black hole (SMBH), and the multi-band
nuclear characteristics, that are similar to those of FRI radio
galaxies. However, in the radio band, while FR0 and FRI share the same
nuclear properties, the kiloparsec-scale diffuse component dominant in
FRI is missing in FR0s. Previous very-long-baseline interferometry
(VLBI) observations of a small sample of FR0s show a complex
structure, mostly symmetric (two-sided jets) with respect to the
central core.
With this project we would like to study the parsec-scale structure in
FR0s in comparison with that of FRI sources. Jets in FRI are
relativistic on the parsec scale and decrease their velocity becoming
subrelativistic on the kiloparsec scale. We would like to test whether
this result also applies to the jets in FR0s or, alternatively,
whether they are subrelativistic on the parsec scale. This might be
the reason why they are unable to grow, because of instabilities,
related to a low jet bulk velocity.
To this end we observed 18 FR0 galaxies with the VLBA at 1.5 and 5GHz
and/or with the EVN at 1.7GHz and produced detailed images at
milliarcsec resolution of their nuclear emission to study the jet and
core structure.
All sources have been detected but one. Four sources are unresolved,
even in these high-resolution images; jets have been detected in all
other sources. We derived the distribution of the jet-to-counter-jet
ratio of FR0s and found that it is significantly different from that
of FRIs, suggesting different jet bulk speed velocities. Conclusions.
Combining the present data with published data of FR0 with VLBI
observations, we derive that the radio structure of FR0 galaxies shows
strong evidence that parsec-scale jets in FR0 sources are mildly
relativistic with a bulk velocity on the order of 0.5c or less. A jet
structure with a thin inner relativistic spine surrounded by a
low-velocity sheath could be in agreement with the SMBH and jet launch
region properties
Description:
Among the 25 FR0s studied with JVLA observations in the A array (Baldi
et al. 2015A&A...576A..38B 2015A&A...576A..38B, 2019MNRAS.482.2294B 2019MNRAS.482.2294B), we selected sources
with a core flux density at 1.4GHz greater than 20 mJy and z<0.05.
The 11 sources selected were observed with EVN at 1.7GHz.
Observations were carried in May 2019 in phase reference mode with a
data rate of 1024 Mbit/sec (project EG100). Nearby phase calibrators
selected from the VLBA calibrator list, and target sources were
observed with a ∼5min cycle. The total observing time was ∼2hr/source
with at least 60 min on the target source and the remaining time on
calibrator source and motion.
Moreover, in the time range September - December 2021 we observed 11
FR0s with the VLBA at 5 and 1.5GHz (project BG272). Selected
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 119 17 List of fits images
fits/* . 17 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- 22 I3 --- Nx Number of pixels along X-axis
24- 26 I3 --- Ny Number of pixels along Y-axis
28- 37 A10 "date" Obs.date Observation date
39- 45 F7.5 GHz Freq Observed frequency
47- 50 I4 Kibyte size Size of FITS file
52- 62 A11 --- FileName Name of FITS file, in subdirectory fits
64-119 A56 --- Title Title of the FITS file
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Acknowledgements:
Gabriele Giovannini, ggiovann(at)ira.inaf.it
(End) Patricia Vannier [CDS] 21-Mar-2023