The water maser in the INTEGRAL source IGR J16385-2057
In a search for 22-GHz water maser emission of a sample of
AGN discovered by INTEGRAL/IBIS in the hard X-ray band,
using the Green Bank Telescope, a luminous water maser has
been detected in the galaxy IGR J16385-2057.
At optical wavelengths, the galaxy (z ~ 0.027) is
morphologically classified as an elliptical galaxy and,
spectroscopically, as a Narrow Line Seyfert 1. Indeed, the
detection of 22-GHz water maser emission in IGR J16385-2057
is particulary relevant, since -so far- only a handful of
elliptical galaxies has been detected in such a transition.
Furthermore, the radio morphology of the galaxy shows two
extended lobes of optically-thin synchrotron emission almost
symmetrically bracketing a compact radio core associated with
the optical body of the galaxy, thus seemingly resembling the
structure of a radio galaxy. If this will be confirmed by the
on-going radio follow up observations, IGRJ 16385-2057 would
then represent one of the rare cases of radio galaxies
hosting a water maser source.
The figure shows the NRAO VLA Sky Survey radio continuum
map at 1.4 GHz (green contours) of IGRJ 16385-2057 overlayed
onto a DSS optical image. The inset shows the water maser
spectrum detected in the nucleus of IGR J16385-2057 with the
Green Bank Telescope. The water maser emission is composed of
a number of narrow features clustered in the proximity of the
systemic velocity of the galaxy at about 8065 km/s (indicated
by the vertical line segment).
Image Credits and Notes:
Extragalactic Radioastronomy Group (ERG) - Osservatorio
Astronomico di Cagliari. The picture has been produced with the
collaboration of Matteo Murgia using the software "Synage++".
