J/A+A/695/A118 1cm and 7mm VLBI images of sixteen AGN (Boccardi+, 2025)
Jet formation studies in AGN: A search for new targets.
Boccardi B., Ricci L., Madika E., Bartolini V., Bach U., Grandi P.,
Torresi E., Krichbaum T.P., Zensus J.A.
<Astron. Astrophys. 695, A118 (2025)>
=2025A&A...695A.118B 2025A&A...695A.118B (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, radio ; Active gal. nuclei ; VLBI ; Radio continuum
Keywords: instrumentation: high angular resolution -
instrumentation: interferometers - methods: observational -
galaxies: active - galaxies: jets
Abstract:
In recent years, the jet formation region in active galaxies has been
imaged through millimeter very long baseline interferometry
(mm-VLBI) for a few ideal targets, in particular, M87. An important
leap forward for understanding jet launching could be taken by
identifying a larger number of suitable objects, characterized by
different accretion modes and jet powers.
In this article, we present 1cm and 7mm VLBI data of a sample of 16
poorly explored radio galaxies, comprising both highexcitation (HEGs)
and low-excitation galaxies (LEGs), spanning a broad range in terms of
radio power. There are several -ray emitters among this sample. The
sources proximity (z<0.1) combined with a high black hole mass
(logMBH≳8.5) implies a high spatial resolution in units of
Schwarzschild radii (<103-104RS), necessary for probing the region
where the jet is initially accelerated and collimated. We aim to
identify the best candidates for follow-up observations with current
and future VLBI facilities.
The observations were performed with the High Sensitivity Array (HSA),
including the Eelsberg telescope and the phased Very Large Array
(VLA). The addition of elements with a large collecting area has
allowed us to characterize the sub-parsec properties of these faint
jets and to estimate their core brightness temperature and
orientation.
The number of sources imaged on scales ≲103RS has more than doubled
thanks to the present study. All targets were detected at both
frequencies, with several of them presenting two-sided jet structures.
Several LEG jets show hints of limb brightening. The core brightness
temperatures are generally below the equipartition value, indicating
that equipartition has not yet been reached and/or that the emission
is de-boosted. Among the LEGs in the sample, we identified 3C 31, 3C
66B, and 3C 465 as the most promising, as they combine a relatively
high flux density (>50mJy) with a superb spatial resolution (<500RS)
at 7mm. The powerful HEG 3C 452 is interesting as well, due to its
highly symmetric, two-sided jet base. Most sources are expected to
become prime targets for future experiments with the next generation
Event Horizon Telescope (ngEHT) and next generation Very Large Array
(ngVLA).
Description:
We provide 1cm and 7mm VLBI images of a sample of sixteen poorly
explored radio galaxies, comprising both High-Excitation (HEG) and
Low-Excitation Galaxies (LEG) and spanning a large range in radio
power. The observations were performed using the High Sensitivity
Array, including Effelsberg and the phased-VLA. The combination of the
sources vicinity (z<0.1) with a large black hole mass (Log(M_BH)>8.5)
results in a high spatial resolution in units of Schwarzschild radii
(<103-104R☉), necessary for probing the region where the jet
is initially accelerated and collimated.
These are the FITS files of the images presented in Appendix A, which
can be found at the link: https://doi.org/10.5281/zenodo.14627546 The
file names are formed by the source name, the observing band (K or Q),
and the weighting scheme used in the imaging, uniform (un) or natural
(nat).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 116 52 List of fits files
fits/* . 52 Individual fits files
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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- 51 E11.6 Hz Freq Observed frequency
53- 57 I5 Kibyte size Size of FITS file
59- 76 A18 --- FileName Name of FITS file, in subdirectory fits
77-116 A40 --- Title Title of the FITS file
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Acknowledgements:
Bia Boccardi, bboccardi(at)mpifr-bonn.mpg.de
(End) Patricia Vannier [CDS] 13-Jan-2025