J/A+A/616/A188 M87 jet VLBI images (Kim+, 2018)
The limb-brightened jet of M87 down to the 7 Schwarzschild radii scale.
Kim J.-Y., Krichbaum T.P., Lu R.-S., Ros E., Bach U., Bremer M.,
de Vicente P., Lindqvist M., Zensus J.A.
<Astron. Astrophys. 616, A188 (2018)>
=2018A&A...616A.188K 2018A&A...616A.188K (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Galaxies, radio ; Interferometry
Keywords: galaxies: active - galaxies: jets - galaxies : individual: M87 -
techniques: interferometric
Abstract:
Messier 87 (M87) is one of the nearest radio galaxies with a prominent
jet extending from sub-pc to kpc scales. Because of its proximity and
the large mass of its central black hole (BH), it is one of the best
radio sources for the study of jet formation. We study the physical
conditions near the jet base at projected separations from the BH of
∼7-100 Schwarzschild radii (Rsch). Global mm-VLBI Array (GMVA)
observations at 86GHz (λ=3.5mm) provide an angular resolution
of ∼50µarcsec, which corresponds to a spatial resolution of only
7Rsch and reach the small spatial scale. We use five GMVA data sets of
M87 obtained from 2004 to 2015 and present new high angular resolution
VLBI maps at 86GHz. In particular, we focus on the analysis of the
brightness temperature, the jet ridge lines, and the ratio of jet to
counter-jet. The imaging reveals a parabolically expanding
limb-brightened jet which emanates from a resolved VLBI core of
~(8-13)Rsch in size. The observed brightness temperature of the core
at any epoch is ~(1-3)x1010K, which is below the equipartition
brightness temperature and suggests magnetic energy dominance at the
jet base. We estimate the diameter of the jet at its base to be ∼5Rsch
assuming a self-similar jet structure. This suggests that the sheath
of the jet may be anchored in the very inner portion of the accretion
disk.
The image stacking reveals faint emission at the center of the
edge-brightened jet on sub-pc scales. We discuss its physical
implication within the context of the spine-sheath structure of the
jet.
Description:
(i) Five 86GHz VLBI images of the inner jet in M87 obtained from
observations between 2004 and 2015.
(ii) Two stacked 86GHz VLBI images of the M87 jet obtained by image
stacking (for details, see Sect. 3.3 of the paper).
Objects:
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RA (2000) DE Designation(s)
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12 30 49.42 +12 23 28.0 M87 = NGC 4486
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 113 7 List of fits images
fits/* . 7 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- 47 F7.4 GHz Freq Observed frequency
49- 52 I4 Kibyte size Size of FITS file
54- 65 A12 --- FileName Name of FITS file, in subdirectory fits
67-113 A47 --- Title Title of the FITS file
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Acknowledgements:
Jae-Young Kim, jykim(at)mpifr-bonn.mpg.de
(End) Jae-Young KIM [MPIfR, Germany], Patricia Vannier [CDS] 06-Aug-2018