Radial Velocities and Line Strengths of Emission Lines across the Nuclear Disk of M31
Abstract
Image-tube spectra have been obtained at sixteen position angles across the nuclear bulge of I31, at a dispersion of 28 A mm '. Emission lines of H , [N ii] XX6548 and 6583, [S iii xx6717 and 6731, He a X5876, and [0 iii] X5007 are observed. From the measured line-of-sight velocities of the excited gas across the inner 400 pc, we obtain the following model. Gas is concentrated in a very thin rotating disk with rotational velocities of the gas increasing to V = 200 km ; the rotation is not axially symmetric. Expansion motions as large as 100 km I exist in position angles and 248 278 , but less than 0.01 o is leaving the R = 400 pc region. Excess positive velocities observed in one quadrant are correlated with positions of absorbing clouds near the nucleus of M31, and may indicate infalling motions of low lying clouds. Extreme density fluctuations are present; the total mass of ionixed gas to k = 400 pc is probably less than 10 ?o. Over this region the average surface brightness is S = 0.2 X 10- ergs 1 sterad-' in Ha, and twice this in [N ii] X6583
- Publication:
-
The Astrophysical Journal
- Pub Date:
- November 1971
- DOI:
- 10.1086/151186
- Bibcode:
- 1971ApJ...170...25R