Issue |
A&A
Volume 419, Number 3, June I 2004
|
|
---|---|---|
Page(s) | 887 - 896 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361:20040998 | |
Published online | 07 May 2004 |
An embedded circumnuclear disk in Mrk 273
1
Kapteyn Institute, University of Groningen, PO Box 800, 9700 AV Groningen, The Netherlands
2
ASTRON, Westerbork Observatory, PO Box 2, 7990 AA Dwingeloo, The Netherlands
Corresponding author: H.-R. Klöckner, hrkloeck@astro.rug.nl
Received:
8
January
2004
Accepted:
13
February
2004
Radio observations using very long baseline interferometry
(VLBI) and the Westerbork interferometer have been carried out to
study the hydroxyl Megamaser emission in Mrk 273 at different spatial
resolutions. Line and continuum observations were carried out by the
European VLBI network (EVN) at 1.6 GHz and display a number of
distinct structural components in the central arcsec2 region.
The observed continuum emission shows three prominent regions with
both flat and steep spectral indexes.
The hydroxyl (OH) emission detected by the EVN measurements accounts
for only 12 percent of the total OH emission in Mrk 273, but it does
show the same dominant 1667 MHz line emission components as the WSRT observations. The spatial distribution of the maser emission provides
a high resolution view of the molecular environment in the nuclear
region. The OH emission has only been detected toward a distinct radio
source in the northern nucleus with a spatial extent of 108 pc. The OH emission is only partially superposed on the radio continuum and is
associated with the near-infrared emission source. The low pump
efficiency of the maser and the OH main-line ratio suggest that this
emission originates in an optically thin and unsaturated maser
environment with a complex pumping scheme that cannot be explained by
radiative infrared pumping with a single dust temperature. The
specific line emission pattern and the line-of-sight velocities
indicate the organized structure of an edge-on disk/TORUS with a
Keplerian rotation surrounding a central object with a binding mass of
1.39 ± 0.16 109 M
.
Key words: galaxies: individual: Mrk 273 / masers / galaxies: ISM / galaxies: kinematics and dynamics
© ESO, 2004
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