CHANDRA OBSERVATIONS OF MRK 273: UNVEILING THE CENTRAL AGN
AND THE EXTENDED HOT GAS HALO
X.-Y. Xia(Dept. of Physics, Tianjin Normal University, 300074 Tianjin, China) S.J. Xue (National Astronomical Observatories, Chinese Academy of Sciences, A20 Datun Road, 100012 Beijing, China), S. Mao (Univ. of Manchester, Jodrell Bank Observatory, Macclesfield, Cheshire SK11 9DL, UK),
Abstract
We report X-ray results of the ultraluminous
IRAS galaxy Mrk 273 obtained using the ACIS-S3 instrument on board
Chandra. The high resolution X-ray image, for the first time, reveals
a compact hard X-ray nucleus. Its position is coincident with the
northern nucleus identified in the optical, infrared, radio and in
molecular CO maps. Its X-ray energy distribution is well described by
a heavily obscured AGN spectra with an absorbed power-law plus a
narrow FeK
emission line at 6.4 keV. The neutral hydrogen
column density is about
,
implying an
absorption-corrected X-ray luminosity (0.1-10 keV) for the nucleus of
for
.
The X-ray properties therefore firmly establishes the
northern nucleus of Mrk 273 as a Seyfert 2 active galactic nucleus.
There are also bright soft X-ray clumps and diffuse soft X-ray emissions
surrounding the central hard X-ray nucleus within the
10'' of the nuclear region. Its spectrum can be
fitted by a MEKAL thermal model with
temperature of about 0.8 keV and high metallicity (
)
plus emission lines from
elements and ions. We find
that a soft X-ray clump, about 4'' (projected separation of about 4 kpc)
southwest of the northern hard X-ray
nucleus, is coincident with a nebula with strong OIII emissions.
Further outside the central region, the Chandra observations reveal
a very extended hot halo in Mrk 273. The X-ray halo
encompasses the entire optical tidal tail and plume, with a
projected size of about
.
The total soft X-ray luminosity (0.1-2.4 keV) of the hot halo is
,
in the range of the soft X-ray luminosity of bright elliptical galaxies.
The temperature of the hot gas is about 0.62 keV with
a low metallicity (
).
We discuss the nature of AGN and the
implications of our results on the origin of X-ray halos
in elliptical galaxies.
CATEGORY: ACTIVE GALAXIES AND QUASARS