J/ApJ/833/288 Radio obs. of NGC 6251 jet (Tseng+, 2016)
Structural transition in the NGC 6251 jet: an interplay with the supermassive
black hole and its host galaxy.
Tseng C.-Y., Asada K., Nakamura M., Pu H.-Y., Algaba J.-C., Lo W.-P.
<Astrophys. J., 833, 288-288 (2016)>
=2016ApJ...833..288T 2016ApJ...833..288T (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; Interferometry ; Galaxies, nearby ;
Radio continuum
Keywords: galaxies: active; galaxies: individual: NGC 6251;
galaxies: jets; radio continuum: galaxies
Abstract:
The structure of the NGC 6251 jet on the milliarcsecond scale is
investigated using images taken with the European VLBI Network and the
Very Long Baseline Array. We detect a structural transition of the jet
from a parabolic to a conical shape at a distance of (1-2)x105 times
the Schwarzschild radius from the central engine, which is close to
the sphere of gravitational influence of the supermassive black hole
(SMBH). We also examine the jet pressure profiles with the synchrotron
minimum energy assumption to discuss the physical origin of the
structural transition. The NGC 6251 jet, together with the M87 jet,
suggests a fundamental process of structural transition in the jets of
active galactic nuclei (AGNs). Collimated AGN jets are characterized
by their external galactic medium, showing that AGN jets interplay
with the SMBH and its host galaxy.
Description:
We conducted European VLBI Network (EVN) observations of NGC 6251 on
2013 March 10 at 1.6GHz with the stations at Badary, Svetloe,
Zelenchukskaya (Russia), Effelsberg (Germany), Jodrell Bank (UK),
Medicina, Noto (Italy), Onsala (Sweden), Shanghai, Urumqi (China),
Torun (Poland), and Westerbork (Netherlands).
Archival Very Long Baseline Array (VLBA) data at 5GHz are used and
calibrated in the same manner as the EVN data. Also, 12 epochs of the
VLBA data at 15GHz are obtained from the MOJAVE database (Lister+
2009, J/AJ/137/3718). Observations were conducted during 1998-2013.
We also use a published VLA image of NGC 6251 at 1.4GHz to compare
with the VLBI measurements in Section 4.1. The image, as well as the
calibration processes, is shown in Sambruna+ (2004A&A...414..885S 2004A&A...414..885S).
Observations were conducted on 1995 August 15 using the full VLA in
its A-configuration. The beam is restored to be circular with an FWHM
of 2".
Objects:
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RA (ICRS) DE Designation(s)
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16 32 31.97 +82 32 16.4 NGC 6251 = LEDA 58472
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 66 315 Measurements of the jet radii and
estimated uncertainties
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See also:
J/AJ/152/12 : MOJAVE. XIII. New 15GHz obs. on 1994-2013 (Lister+, 2016)
J/ApJ/784/159 : Revisited jet bending in γ-ray AGNs (Graham+, 2014)
J/AJ/146/120 : MOJAVE. X. Parsec-scale kinematics of AGNs (Lister+, 2013)
J/ApJ/758/84 : Relativistic jets in RRFID database. II. 10yr (Piner+, 2012)
J/AJ/137/3718 : 15GHz monitoring of AGN jets with VLBA (Lister+, 2009)
J/ApJS/171/376 : MOJAVE. III. VLA 1.4GHz images (Cooper+, 2007)
J/AJ/131/1262 : Circular polarization images at 15GHz of AGN jets
(Homan+, 2006)
J/AJ/130/1418 : AGN jet kinematics (Jorstad+, 2005)
J/ApJ/609/539 : Kinematics of parsec-scale radio jets (Kellermann+, 2004)
J/AJ/126/2268 : Velocity dispersions and Mg2 index of galaxies (Wegner+, 2003)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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2 I1 --- Obs [1/9] Observation Code (1)
20- 28 F9.3 mas Dist [0.6/16500] Deprojected axial distance (z)
30- 37 F8.3 mas FWHM [0.5/3094] Fitted Gaussian FWHM of
the jet cross section (φ0)
39- 43 F5.2 mas e_FWHM [0/15]? Fitting uncertainties of FWHM
45- 52 F8.3 mas Rad [0.08/1180] Jet radius (r)
54- 58 F5.2 mas e_Rad [0/17]? Fitting uncertainties of Rad
60- 66 F7.3 mas e_Radt [0.009/400] Total uncertainties of Rad (2)
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Note (1): Observation Code, corresponding to Table 1 as follows:
1 = EVN-i 1.6GHz, RR pol., uniform weighting;
2 = EVN-i 1.6GHz, LL pol., uniform weighting;
3 = EVN-ii 1.6GHz, RR pol., natural weighting;
4 = EVN-ii 1.6GHz, LL pol., natural weighting;
5 = EVN-iii 1.6GHz, RR pol., natural with tapering weighting;
6 = EVN-iii 1.6GHz, LL pol., natural with tapering weighting;
7 = VLBA 5GHz;
8 = VLBA 15GHz (MOJAVE), averaged over 12 epochs;
9 = VLA 1.4GHz, Sambruna et al. (2004A&A...414..885S 2004A&A...414..885S).
See also the "Description" section above.
Note (2): Total uncertainties of r taking the imaging error into account,
which is described in Section 3.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 16-May-2017