Hostname: page-component-586b7cd67f-2brh9 Total loading time: 0 Render date: 2024-11-30T05:14:02.475Z Has data issue: false hasContentIssue false
  • English
  • Français

H2O Megamasers and Black Holes

Published online by Cambridge University Press:  14 August 2015

J. M. Moran
J. M. Moran*
Affiliation:
Harvard-Smithsonian Center for Astrophysics60 Garden Street, Cambridge MA 02138

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

Twenty-one H2O masers have been identified in the nuclei of active galaxies. The detection rate is about 7 percent. Very Long Baseline Interferometric data of four of these maser systems (NGC 4258, NGC 1068, NGC 4945, and NGC 3079) show evidence of Keplerian disks on a subparsec scale. The best example is NGC 4258. There the masers trace a thin warped disk in nearly perfect circular Keplerian motion. If the apparent thinness is indicative of hydrostatic equilibrium, then the kinetic temperature must be less than 1000K, the magnetic field less than 200 mG, and the mass accretion rate less than about α10-3 M⊙/yr, where a is the viscosity parameter. From direct Zeeman measurements the toroidal magnetic field strength is less than 300 mG. The proper motions of the systemic maser feature imply a distance to the galaxy of 7.3 ± 0.3 Mpc. The high-velocity features show no detectable proper motions or accelerations, which confirms the model of circular Keplerian motion, and puts severe constraints on any alternative model. A feature in the systemic group flared to 20 Jy, offering opportunities to study the physics of the maser emission.

Type
II. Joint Discussions
Information
Highlights of Astronomy , Volume 11 , Issue 2: Highlights of Astronomy. As presented at the XXIIIrd General Assembly of the IAU (Part B), 1997 , 1998 , pp. 956 - 959
Copyright
Copyright © Kluwer 1998

References

Braatz, J., Greenhill, L., Moran, J., Wilson, A., and Herrnstein, J. (1997) A VLBA Map of the H2O Maser in the Nucleus of Seyfert 2 Galaxy NGC 1386, BAAS, in press.Google Scholar
Burbidge, E. M. and Burbidge, G. (1997) Ejection of Matter and Energy from NGC 4258, Ap.J. (Lett.) 477, pp. L13–15.Google Scholar
Claussen, M. J. and Lo, K.-Y. (1986) Circumnuclear Water Vapor Masers in Active Galaxies, Ap.J 308, pp. 592–599.CrossRefGoogle Scholar
Claussen, M. J., Diamond, P. J., Braatz, J. A., Wilson, A. S., and Henkel, C. A. (1997) The Water Masers in the Elliptical Galaxy NGC 1052, in preparation.Google Scholar
Goodman, A. A., Crutcher, R. M., Heiles, C., Myers, P. C., and Troland, T. H. (1989) Measurement of Magnetic, Field Strength in the Dark Cloud Barnard I, Ap.J. (Lett.) 338, pp. L61–64.Google Scholar
Greenhill, L. J. (1997) Water in NGC 1068, Proceedings of IAU Colloquium 164, Radio Emission from Galactic and Extragalactic Compact Sources, eds. Taylor, G. B., Wrobel, J. M. and Zensus, J. A.. ASP, San Francisco, in press.Google Scholar
Greenhill, L. J., Jiang, R. D., Moran, J. M., Reid, M. J., Lo, K.-Y., and Claussen, M. J. (1995) Detection of a Subparsec Diameter Disk in the Nucleus of NGC 4258, Ap.J. 440, pp. 619–627.CrossRefGoogle Scholar
Greenhill, L. J., Gwinn, C. R., Antonucci, R., and Barvainis, R. (1996) VLBI Imaging of Water Maser Emission from the Nuclear Torus of NGC 1068, Ap.J. (Lett.) 472, pp. L21–24.CrossRefGoogle Scholar
Greenhill, L. J., Moran, J. M., and Herrnstein, J. R. (1997a) The Distribution of H2O Maser Emission in the Nucleus of NGC4945, Ap.J. (Lett.) 481, pp. L23–26.Google Scholar
Greenhill, L. J., Trotter, A. S., Bragg, A., Moran, J. M., and Herrnstein, J. R. (1997b) A Recurring Flare in the NGC4258 H2O Maser, BAAS, in press.Google Scholar
Herrnstein, J. R. (1997) Observations of the Sub-Parsec Maser Disk in NGC 4258, Ph.D. thesis, Harvard University.Google Scholar
Herrnstein, J. R. (1998) Warps, Jets, and Proper Motions in the Central Parsec of NGC 4258, Proceedings of IAU Symposium 184. Kluwer, Dordrecht, in press.Google Scholar
Herrnstein, J. R., Greenhill, L. J., and Moran, J. M. (1996) The Warp in the Sub-Parsec Scale Molecular Disk in NGC 4258 as an Explanation for Persistent Asymmetries in the Spectrum, Ap.J. 468, pp. L17–20.Google Scholar
Herrnstein, J. R., Moran, J. M., Greenhill, L. J., Inoue, M., Nakai, N., Miyoshi, M., and Diamond, P. (1997a) A 4% Geometric Distance to NGC 4258 from Proper Motions in the Nuclear Water Maser, BAAS, in press.Google Scholar
Herrnstein, J. R., Moran, J. M., Greenhill, L. J., Diamond, P. J., Miyoshi, M., Nakai, N., and Inoue, M. (1997b) Discovery of a Sub-Parsec Jet 4000 Schwarzschild Radii from the Central Engine of NGC 4258, Ap.J. 475, pp. L17–20.Google Scholar
Herrnstein, J. R., Greenhill, L. J., Moran, J. M., Blackman, E. G., and Diamond, P. J. (1998) Polarimetric Observations of the Masers in NGC 4258: An Upper Limit on the Large-Scale Magnetic Field 0.2 pc from the Central Engine, Ap.J, in preparation.CrossRefGoogle Scholar
Miyoshi, M., Moran, J. M., Herrnstein, J., Greenhill, L. J., Nakai, N., Diamond, P. J., and Inoue, M. (1995) Evidence for a Massive Black Hole from High Rotation Velocities in a Sub-parsec Region of NGC 4258, Nature 373, pp. 127–129.CrossRefGoogle Scholar
Moran, J. M. (1997) Dynamical Models of the Maser in NGC 4258, in Emission Lines, ed. Peterson, B. M., Cheng, F. Z., and Wilson, A. S.. ASP, San Francisco, pp. 402–405.Google Scholar
Moran, J. M., Greenhill, L. J., Herrnstein, J., Diamond, P., Miyoshi, M., Nakai, N., and Inoue, M. (1995) Probing Active Galactic Nuclei with H2O Megamasers, Proc. Nat Acad. Sci. 92, pp. 11427–11433.CrossRefGoogle ScholarPubMed
Nakai, N., Inoue, M., Hagiwara, Y., Miyoshi, M., and Diamond, P. (1997) Proceedings of IAU Colloquium 164, Radio Emission from Galactic and Extragalactic Compact Sources, eds. Taylor, G. B., Wrobel, J. M. and Zensus, J. A.. ASP, San Francisco, in press.Google Scholar
Satoh, S., Inoue, M., Nakai, N., and Shibata, K. M. (1997) The Water Maser and Continuum Emission in NGC 3079. Proceedings of IAU Colloquium 164, Radio Emission from Galactic and Extragalactic Compact Sources, eds. Taylor, G. B., Wrobel, J. M. and Zensus, J. A.. ASP, San Francisco, in press.Google Scholar
Trotter, A. S., Greenhill, L. J., Moran, J. M., Reid, M. J., Irwin, J. A., and Lo, K.-Y. (1998) Water Maser Emission and the Parsec-Scale Jet in NGC 3079, Ap.J. 495, in press.Google Scholar