Astronomy and Astrophysics – Astrophysics
Scientific paper
2006-11-28
Astronomy and Astrophysics
Astrophysics
6 pages, 2 figures, to appear in the proceedings of the 8th EVN symposium held in Torun, Poland, September 2006
Scientific paper
One of the fundamental concepts in the unified scheme of AGN is that both Seyfert 1 and Seyfert 2 galaxies harbour supermassive nuclear engines blocked from direct view by an optically and geometrically thick torus. If the pressure is sufficiently high, the torus should mostly be molecular. Although molecular rings with diameters of a few hundred parsecs are common, the expected small scale tori (< 10 pc) have been difficult to detect. Searches for absorption lines of common molecules like CO and OH have mostly yielded non-detections. Before concluding that tori are not molecular, radiative excitation effects, in which coupling to the nonthermal continuum can suppress the opacity in the lowest transitions, deserve some attention and influence our selection of the most favourable transitions to observe. To explore these effects, we modified the search strategy by looking for the higher excited rotational states of OH and by selecting a sample of 31 Seyfert 2 galaxies which are known to have a high X-ray absorbing column. We present here the results of single dish observations of the transitions at 6031 MHz and 6035 MHz, yielding detections in five sources. We also present a spectral line VLBI observation carried out at 13.4 GHz towards the core of Cygnus A, yielding a tentative detection.
Henkel Christian
Roy Alan L.
Violette Impellizzeri C. M.
No associations
LandOfFree
Molecular tori in AGN: a search using excited states of OH does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Molecular tori in AGN: a search using excited states of OH, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Molecular tori in AGN: a search using excited states of OH will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-350176