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Water maser emission from X-ray-heated circumnuclear gas in active galaxies
Abstract
We have modeled the physical and chemical conditions present within dense circumnuclear gas that is irradiated by X-rays from an active galactic nucleus. Over a wide range of X-ray fluxes and gas pressures, the effects of X-ray heating give rise to a molecular layer at temperatures of 400-1000 K within which the water abundance is large. The physical conditions within this molecular layer naturally give rise to collisionally pumped maser emission in the 6_16_-5_23_ 22 GHz transition of ortho-water, with predicted maser luminosities of 10^2+/-0.5^ L_sun_ per pc^2^ of illuminated area. Given plausible assumptions about the geometry of the source and about the degree to which the maser emission is anisotropic, such surface luminosities are sufficient to explain the large apparent luminosities observed in water maser sources that are associated with active galactic nuclei.
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Citations
Cited by
VLBI Imaging of Water Maser Emission from the Nuclear Torus of NGC 1068
Greenhill, L. J., Gwinn, C. R., Antonucci, R., & Barvainis, R. (1996) · The Astrophysical Journal · doi:10.1086/310346 · Cited by 260
Evidence for a Geometrically Thick Self‐Gravitating Accretion Disk in NGC 3079
Kondratko, P. T., Greenhill, L. J., & Moran, J. M. (2005) · The Astrophysical Journal · doi:10.1086/426101 · Cited by 140
Water Maser Emission and the Parsec‐Scale Jet in NGC 3079
Trotter, A. S., Greenhill, L. J., Moran, J. M., Reid, M. J., Irwin, J. A., & Lo, K. (1998) · The Astrophysical Journal · doi:10.1086/305335 · Cited by 112
Metadata
- Authors
- Neufeld, D. A., Maloney, P. R., & Conger, S.
- Venue
- The Astrophysical Journal
- Publisher
- American Astronomical Society
- Published
- 1994-12
- Volume
- 436
- Pages
- L127
- ISSN
- 0004-637X (ISSN-L)
- 1538-4357
- OpenAlex
- W2003948574
- Cited by
- 194
- References
- 0
- FWCI
- 12.29
- Type
- journal article
- Language
- en
- Open access
- closed
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- CoChat. (2026). Citation check: Water maser emission from X-ray-heated circumnuclear gas in active galaxies. https://app.cochat.ai/papers/10.1086/187649
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- Neufeld, D. A., Maloney, P. R., & Conger, S. (1994). Water maser emission from X-ray-heated circumnuclear gas in active galaxies. The Astrophysical Journal. https://doi.org/10.1086/187649
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