GBT01A-014

Detecting High-Velocity Masers to Reveal Nuclear Disks in Nearby AGNs

Abstract

One of the most spectacular results in recent years of radio astronomy has been the discovery of a sub-pc disk in the nucleus of the active galaxy NGC 4258. The interpreted geometry and kinematics are based on observations of the water maser spectrum originating in the thin, edge-on disk. From the masers we get the mass of the central black hole, the structure of the accreting gas, a glimpse into the jet/disk interface, and a geometrical measurement of the distance to the galaxy independent of the standard techniques. Critical to revealing the disk is the detection of maser components from the projected edges of the disk, which in NGC 4258 are separated from the systemic velocity by +/- 1000 km/s. Maser components as widely separated in velocity as this have not yet been detected in the other known megamasers. We propose to use the GBT in a search for high-velocity components in the 16 maser-detected galaxies accessible from the Green Bank site. The unsurpassed K-band sensitivity of the GBT and 800 MHz bandwidth spectrometer capable of observing at high spectral resolution make this telescope ideal for detecting high-velocity maser lines.

**Investigators**
Name	Other *	Institution	Email	Phone
James Braatz	PI	NRAO	jbraatz@nrao.edu	304-456-2327
Lincoln Greenhill		Harvard-Smithsonian	greenhill@cfa.harvard.edu	617 495-7194

* PI = Principal Investigator; T = Thesis observations; S = Student

Front Ends

Gregorian K(18.0 to 26.5 GHz)

Back Ends

GBT Spectrometer

Type of Observing

Spectroscopy

Switching Type

Position switching

Allocated time: 40.00 hours.

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