22 GHz Water Maser Search in 37 Nearby Galaxies - Four New Water Megamasers in Seyfert 2 and OH Maser/Absorber Galaxies

Abstract

We report four new 22 GHz water masers found in a Green Bank Telescope search toward 37 nearby objects. Our goal was to find new maser galaxies, AGN disk-masers, and objects where both hydroxyl and water maser species coexist. We observed 37 sources within 250 Mpc that were selected by high X-ray luminosity (L_X > 10^40 W) and high absorbing column density (N_H ~ 10^22 cm^-2). Sources also included dual or triple AGN and interacting systems. We further included objects detected in hydroxyl (OH). The selection consisted of 16 new sources, 13 previous non-detections to follow up with a factor ten higher sensitivity, 10 OH masers and one deep OH absorber, of which 37 were observed. Water megamasers were detected towards the Sy 2 galaxy 2MFGC 13581 (a disk-maser), towards the 6 GHz OH absorber NGC 4261 (3C 270 with a twin-jet and dusty torus; broad water maser emission), and towards the two 1.6 GHz OH maser sources IRAS 17526+3253 and IRAS 20550+1656 (possible star formation water masers). We set upper limits on 33 non-detections. The search increased the number of known "dual-species" objects containing both OH and H2O masers to eight. The detection rate was 25 % in OH galaxies and 11 % overall. Combined with other searches, a total of 95 objects have now been searched for both OH and H2O masers. We found the overall dual-species detection rate (8 in 95) to be of the order of the joint probability of both species independently occurring in the same object (1 % lower bound). However, this needs to be verified by a more detailed analysis of selection criteria. Lastly, we see a lack of H2O kilomasers in OH megamaser objects already noted by Tarchi et al. (2011). This may be due to sensitivity bias rather than astrophysical reasons.

8 pages, 2 figures, accepted and to be published in A&A

References in corpus (5)

• Prevalence of High X-ray Obscuring Columns among AGN that Host H${}_2$O Masers
• Discovery of Water Maser Emission in Five AGN and a Possible Correlation Between Water Maser and Nuclear 2-10 keV Luminosities
• Positional Coincidence of H2O Maser and a Plasma Obscuring Torus in Radio Galaxy NGC 1052
• The water megamaser in the merger system Arp299
• OH main line masers in the M82 starburst

Cited by in corpus (9)

• Estimating Masses of Supermassive Black Holes in Active Galactic Nuclei from the Halpha Emission Line
• The Hydroxyl-Water Megamaser Connection. I. Water Emission Toward OH Megamaser Hosts
• A More Efficient Search for H2O Megamaser Galaxies : The Power of the X-ray and Mid-infrared Photometry
• Gemini IFU, VLA, and HST observation of the OH Megamaser Galaxy IRAS17526+3253
• Radio properties of the OH megamaser galaxy IIZw 096
• Water megamaser and central black hole masses in a large sample of galaxies
• A Spectral Analysis of the Centimeter Regime of Nearby Galaxies: RRLs, Excited OH, and NH${}_3$
• Searches for H${}_2$O Masers toward Narrow-Line Seyfert 1 galaxies
• Very Long Baseline Interferometry imaging of H2O maser emission in the nearby radio galaxy NGC 4261