Observational Evidence for Massive Black Holes in the Centers of Active Galaxies

Abstract

Naturally occurring water vapor maser emission at 1.35 cm wavelength provides an accurate probe for the study of accretion disks around highly compact objects, thought to be black holes, in the centers of active galaxies. Because of the exceptionally fine angular resolution, 200 microarcseconds, obtainable with very long baseline interferometry, accompanied by high spectral resolution, < 0.1 km/s, the dynamics and structures of these disks can be probed with exceptional clarity. The data on the galaxy NGC4258 are discussed here in detail. The mass of the black hole binding the accretion disk is 3.9 times 10^7 solar masses. Although the accretion disk has a rotational period of about 800 years, the physical motions of the masers have been directly measured with VLBI over a period of a few years. These measurements also allow the distance from the earth to the black hole to be estimated to an accuracy of 4 percent. The status of the search for other maser/black hole candidates is also discussed.

24 pages, 11 figures, latex, uses aaspp4 style file. To be published in the Journal of Astronomy and Astrophysics (India), proceedings of the Discussion Meeting on the Physics of Black Holes, Bangalore, India: December 1997

References in corpus (2)

• A 4% Geometric Distance to the Galaxy NGC4258 from Orbital Motions in a Nuclear Gas Disk
• Megamaser Disks in Active Galactic Nuclei

Cited by in corpus (19)

• Supermassive Black Holes in Galactic Nuclei: Past, Present and Future Research
• Relativistic Dynamics and Extreme Mass Ratio Inspirals
• The Discovery of H2O Maser Emission in Seven AGN and at High Velocities in the Circinus Galaxy
• Toward a New Distance to the Active Galaxy NGC 4258: II. Centripetal Accelerations and Investigation of Spiral Structure
• Constraining scalar fields with stellar kinematics and collisional dark matter
• Accretion of stars on to a massive black hole: A realistic diffusion model and numerical studies
• Low-luminosity Active Galaxies and their Central Black Holes
• Probing the Magnetic Field at Sub-Parsec Radii in the Accretion Disk of NGC 4258
• A figure of merit for black hole mass measurements with molecular gas
• A search for extragalactic H2O maser emission towards IRAS galaxies II - Discovery of an H2O maser in the Seyfert 1 galaxy NGC 4051
• A search for extragalactic H2O maser emission towards IRAS galaxies - Detection of a maser from an infrared-luminous merger, NGC6240
• SMA Imaging of the Maser Emission from the H30$\alpha$ Radio Recombination Line in MWC349A
• VLBI study of water maser emission in the Seyfert 2 galaxy NGC5793. I: Imaging blueshifted emission and the parsec-scale jet
• Location of H2O maser in the double-nuclei system of NGC6240
• The relation between the mid-infrared emission and Black Hole Mass in Active Galactic Nuclei: A direct way to probe black hole growth?
• Response of circumnuclear water masers to luminosity changes in an active galactic nucleus
• 183 GHz water megamasers in active galactic nuclei: a new accretion disk tracer
• Variability in extragalactic class I methanol masers: New maser components toward NGC4945 and NGC253
• Closed Timelike Curves in Relativistic Computation