Water megamaser emission in hard X-ray selected AGN
| Autor: | Angela Malizia, Andrea Tarchi, Paola Castangia, Loredana Bassani, Pietro Ubertini, Angela Bazzano, Francesca Panessa |
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| Rok vydání: | 2020 |
| Předmět: |
Active galactic nucleus
Infrared Astrophysics::High Energy Astrophysical Phenomena Megamaser FOS: Physical sciences Context (language use) Astrophysics Astrophysics::Cosmology and Extragalactic Astrophysics 01 natural sciences Luminosity law.invention law 0103 physical sciences Astrophysics::Solar and Stellar Astrophysics Maser 010303 astronomy & astrophysics Astrophysics::Galaxy Astrophysics Physics High Energy Astrophysical Phenomena (astro-ph.HE) 010308 nuclear & particles physics Astronomy and Astrophysics Astrophysics - Astrophysics of Galaxies Galaxy Black hole Space and Planetary Science Astrophysics of Galaxies (astro-ph.GA) Astrophysics - High Energy Astrophysical Phenomena |
| DOI: | 10.48550/arxiv.2006.08280 |
| Popis: | Water megamaser emission at 22 GHz has proven to be a powerful tool for astrophysical studies of AGN allowing an accurate determination of the central black hole mass and of the accretion disc geometry and dynamics. However, after searches among thousands of galaxies, only ~ 200 of them have shown such spectroscopic features, most of them of uncertain classification. In addition, the physical and geometrical conditions under which maser activates are still unknown. In this work we aim at characterizing the occurrence of water maser emission in an unbiased sample of AGN, investigating the relation with the X-ray properties and the possible favorable geometry needed to detect water maser. We have searched for 22 GHz maser emission in a hard X-ray selected sample of AGN, taken from the INTEGRAL/IBIS survey above 20 keV. Of the 380 sources in the sample, only half have water maser data. We have also considered a sub-sample of 87 sources, volume limited, for which we obtained new Green Bank Telescope and Effelsberg observations (for 35 sources), detecting one new maser and increasing its radio coverage to 75%. The detection rate of water maser emission in the total sample is 15+/-3%, this fraction raises up to 19+/-5% for the complete sub-sample, especially if considering type 2 and Compton thick AGN. These results demonstrate that the hard X-ray selection may significantly enhance the maser detection efficiency over comparably large optical/infrared surveys. A possible decline of the detection fraction with increasing luminosity might suggest that an extreme luminous nuclear environment does not favour maser emission. The large fraction of CT AGN with water maser emission could be explained in terms of geometrical effects, being the maser medium the very edge-on portion of the obscuring medium. Comment: 21 pages, 3 figures. Accepted for publication in A&A June 2020 |
| Databáze: | OpenAIRE |
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