Submillimeter H2O Maser in Circinus Galaxy - A New Probe for the Circumnuclear Region of Active Galactic Nuclei

Abstract

We present the first detection of extragalactic submillimeter H2O maser in the 321 GHz transition toward the center of Circinus galaxy, the nearby Type 2 Seyfert using the Atacama Large Millimeter/Submillimeter Array. We find that Doppler features of the detected 321 GHz H2O maser straddle the systemic velocity of the galaxy as seen in the spectrum of the known 22 GHz H2O maser in the galaxy. By comparing the velocities of the maser features in both transitions, it can be deduced that the 321 GHz maser occurs in a region similar to that of the 22 GHz maser, where the sub-parsec-scale distribution of the 22 GHz maser was revealed by earlier very long baseline interferometry observations. The detected maser features remain unresolved at the synthesized beam of ~0".66 (~15 pc) and coincide with the 321 GHz continuum peak within small uncertainties. We also present a tentative detection of the highest velocity feature (redshifts up to ~635 km/s) in the galaxy. If this high-velocity feature arises from a Keplerian rotating disk well established in this galaxy, it is located at a radius of ~0.018 pc (~1.2 x 10^5 Schwarzschild radii), which might probe molecular material closest to the central engine.

6 pages, 4 figures

References in corpus (4)

• The Megamaser Cosmology Project. III. Accurate Masses of Seven Supermassive Black Holes in Active Galaxies with Circumnuclear Megamaser Disks
• The Large-Scale Atomic and Molecular Gas in the Circinus Galaxy
• Low-luminosity Extragalactic Water Masers toward M82, M51, and NGC4051
• Submillimeter Array Observations of 321 GHz Water Maser Emission in Cepheus A

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• TeraHertz Exploration and Zooming-in for Astrophysics (THEZA): ESA Voyage 2050 White Paper
• Physical conditions of molecular gas in the Circinus galaxy: Multi-J CO and CI 1-0 observations
• Detection of 183 GHz water megamaser emission towards NGC 4945
• A multiwavelength-motivated X-ray model for the Circinus Galaxy
• Sub-arcsecond imaging of the water emission in Arp 220
• ALMA imaging of the cold molecular and dusty disk in the type 2 active nucleus of the Circinus galaxy
• Submillimeter H${}_2$O megamasers in NGC 4945 and the Circinus galaxy
• Search for sub-millimeter H2O masers in active galaxies - the detection of a 321 GHz H2O maser in NGC4945
• Infrared Interferometry and AGNs: Parsec-scale Disks and Dusty Outflows
• 183 GHz water megamasers in active galactic nuclei: a new accretion disk tracer
• Second Epoch ALMA Observations of 321 GHz Water Maser Emission in NGC 4945 and the Circinus Galaxy
• ALMA detection of millimetre 183 GHz H2O maser emission in the Superantennae galaxy at z ~ 0.06
• High-Resolution Imaging of Water Maser Emission in the active galaxies NGC 6240 and M51
• ALMA Detection of 321 GHz water maser emission in the radio galaxy NGC 1052
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• Extragalactic maser surveys