J/A+A/647/A67 Jet collimation in NGC 315 (Boccardi+, 2021)
Jet collimation in NGC 315 and other nearby AGN.
Boccardi B, Perucho M., Casadio C., Grandi P., Macconi D., Torresi E.,
Pellegrini S., Krichbaum T.P., Kadler M., Giovannini G., Karamanavis V.,
Ricci L., Madika E., Bach U., Ros E., Giroletti M., Zensus J.A.
<Astron. Astrophys. 647, A67 (2021)>
=2021A&A...647A..67B 2021A&A...647A..67B (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei; Galaxies, radio ; Radio sources ; VLBI
Keywords: galaxies: active - galaxies: jets -
instrumentation: high angular resolution -
galaxies: individual: NGC 315
Abstract:
The collimation of relativistic jets in galaxies is a poorly
understood process. Detailed radio studies of the jet collimation
region have been performed so far in a few individual objects,
providing important constraints for jet formation models. However, the
extent of the collimation zone as well as the nature of the external
medium possibly confining the jet are still debated.
In this article, we present a multifrequency and multiscale analysis
of the radio galaxy NGC 315, including the use of mm-VLBI data up to
86GHz, aimed at revealing the evolution of the jet collimation
profile. We then consider results from the literature to compare the
jet expansion profile in a sample of 27 low-redshift sources, mainly
comprising radio galaxies and BL Lacs, which were classified based on
the accretion properties as low-excitation (LEG) and high-excitation
(HEG) galaxies.
We propose that the jet collimation in NGC 315 is completed on
sub-parsec scales. A transition from a parabolic to conical jet shape
is detected at zt=0.58±0.28-parsecs or ∼5x10^3& Schwarzschild
radii (Rs) from the central engine, a distance which is much smaller
than the Bondi radius, rB∼92pc, estimated based on X-ray data. The jet
in this and in a few other LEG in our sample may be initially confined
by a thick disk extending out to ∼103-104R☉. A comparison
between the mass-scaled jet expansion profiles of all sources
indicates that jets in HEG are surrounded by thicker disk-launched
sheaths and collimate on larger scales with respect to jets in LEG.
These results suggest that disk winds play an important role in the
jet collimation mechanism, particularly in high-luminosity sources.
The impact of winds on the origin of the FRI and FRII dichotomy in
radio galaxies is also discussed.
Description:
VLBI and VLA images (FITS) of the giant radio galaxy NGC 315 used to
reconstruct the jet collimation profile from sub-parsec to Mega-parsec
scales. This is a multi-epoch and multi-frequency data set spanning
the 1GHz/86GHz frequency regime.
Objects:
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RA (2000) DE Designation(s)
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00 57 48.88 +30 21 08.8 NGC 315 = LEDA 3455
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 108 20 List of fits images
fits/* . 20 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 "date" Obs.date Observation date
41- 48 F8.5 GHz Freq Observed frequency
50- 54 I5 Kibyte size Size of FITS file
56- 67 A12 --- FileName Name of FITS file, in subdirectory fits
69-108 A40 --- Title Title of the FITS file
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Acknowledgements:
Bia Boccardi, bboccardi(at)mpifr.de
(End) Patricia Vannier [CDS] 01-Mar-2021