2016A&A...585A..33B


C.D.S. - SIMBAD4 rel 1.7 - 2019.10.19CEST13:30:49

2016A&A...585A..33B - Astronomy and Astrophysics, volume 585A, 33-33 (2016/1-1)

The stratified two-sided jet of Cygnus A. Acceleration and collimation.

BOCCARDI B., KRICHBAUM T.P., BACH U., MERTENS F., ROS E., ALEF W. and ZENSUS J.A.

Abstract (from CDS):

High-resolution Very-Long-Baseline Interferometry (VLBI) observations of relativistic jets are essential for constraining the fundamental parameters of jet formation models. At a distance of 249Mpc, Cygnus A is a unique target for such studies, since it is the only Fanaroff-Riley Class II radio galaxy for which a detailed subparsec scale imaging of the base of both jet and counter-jet can be obtained. Observing at millimeter wavelengths unveils those regions that appear self-absorbed at longer wavelengths and enables an extremely sharp view toward the nucleus to be obtained. We performed 7mm Global VLBI observations, achieving ultra-high resolution imaging on scales down to 90µas. This resolution corresponds to a linear scale of only ∼400 Schwarzschild radii (for MBH=2.5x109M). We studied the kinematic properties of the main emission features of the two-sided flow and probed its transverse structure through a pixel-based analysis. We suggest that a fast and a slow layer with different acceleration gradients exist in the flow. The extension of the acceleration region is large (∼104RS), indicating that the jet is magnetically driven. The limb brightening of both jet and counter-jet and their large opening angles (φJ∼10°) strongly favour a spine-sheath structure. In the acceleration zone, the flow has a parabolic shape (r∝z0.55±0.07). The acceleration gradients and the collimation profile are consistent with the expectations for a jet in ``equilibrium'', achieved in the presence of a mild gradient of the external pressure (p∝z–k, k≤2).

Abstract Copyright:

Journal keyword(s): galaxies: jets - galaxies: active - instrumentation: high angular resolution

Simbad objects: 7

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Number of rows : 7

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2019
#notes
1 3C 84 Sy2 03 19 48.1597607660 +41 30 42.114155434   13.10 12.48 11.09   ~ 3460 3
2 3C 273 BLL 12 29 06.6996828061 +02 03 08.598846466   13.05 14.830 14.11   ~ 5242 1
3 M 87 BiC 12 30 49.42338230 +12 23 28.0438581 10.16 9.59 8.63   7.49 ~ 6026 3
4 NAME Centaurus A Sy2 13 25 27.61509104 -43 01 08.8056025   8.18 6.84 6.66   ~ 3886 3
5 4C 39.49 BLL 16 53 52.21668494 +39 45 36.6089458 14.09 14.15 13.29 8.26   ~ 1876 2
6 NAME Cyg A Sy2 19 59 28.35645829 +40 44 02.0966496   16.22 15.10     ~ 2057 2
7 QSO J2015+371 BLL 20 15 28.72976962 +37 10 59.5148505     21.82 21.4   ~ 232 2

    Equat.    Gal    SGal    Ecl

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2019.10.19-13:30:49

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