H$_2$O Megamasers as Probes of Molecular Gas in AGN's

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Session 20 -- AGN Environments
Display presentation, Monday, 9, 1995, 9:20am - 6:30pm

[20.01] H$_2$O Megamasers as Probes of Molecular Gas in AGN's

J.A. Braatz (UMD), A.S. Wilson (UMD and STScI), C. Henkel (MPIfR)

In our ongoing project to survey nearby AGN's for H$_2$O maser emission, we have recently discovered 3 new H$_2$O megamaser sources with the Parkes 64-m telescope. They are NGC 1386, ESO 103--G35, and IC 2560. To date, this project has provided 8 new sources to the list of H$_2$O megamasers, which now numbers 13 in all. We have begun to accumulate various morphological, photometric, and geometric data for all of the sources in our sample ($\sim$ 250 in total), and by comparing properties of the general sample population with those of the H$_2$O megamaser population, we are beginning to uncover several intriguing trends. The H$_2$O megamaser sources seem to prefer active galaxies with heavily obscured nuclei (Seyfert 2 galaxies and obscured LINERs), and they may also prefer sources with inclined galactic disks. Several of the megamaser sources have been found to have extremely large column densities based on X-ray spectra. Recent studies of the physical conditions of near-nuclear molecular gas in AGN's suggests that H$_2$O megamasers should be common in molecular gas near the powerful X-ray sources in the AGN's. Nevertheless, only about 6\% of these sources have observable emission. We will present several possibilities to explain the apparent deficit.

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