A Subkiloparsec Disk in Markarian 231

• Published in: The Astronomical journal 1998-03, Vol.115 (3), p.928-937
• Main Authors: Carilli, C. L, Wrobel, J. M, Ulvestad, J. S
• Format: Article
• Language: English
• ISSN: 1538-3881; 0004-6256; 1538-3881
• DOI: 10.1086/300253

We present imaging with the Very Long Baseline Array of the neutral hydrogen 21 cm absorption-line system seen toward the nuclear regions of Mrk 231 at z(solar) = 0.04217, and imaging of the radio continuum emission at 1.4 GHz on scales ranging from a few parsecs to a few hundred parsecs. These data indicate the existence of a subkiloparsec gas disk in Mrk 231, as seen in H I 21 cm absorption and in radio continuum emission. The radio continuum morphology is consistent with a disk of maximum radius of 440 mas (260/h pc), at an inclination angle of 45 deg, with a major axis oriented east-west. The H I 21 cm absorption shows an east-west gradient in position and velocity of about +/- 110 km/s out to radii of 100 mas (60/h pc). We identify this H I and radio continuum disk as the inner part of the molecular disk seen on a factor of 3 larger scale. The physical conditions for the thermal and nonthermal gas in the subkiloparsec disk of Mrk 231 are similar to those proposed for compact nuclear starburst galaxies and, in particular, to the conditions proposed for the subkiloparsec gas disk in Arp 220. From the neutral hydrogen velocity field we derive a gravitational mass enclosed within a 50 /h pc radius of 3 x 10 exp 8/h solar mass, and from the radio continuum emission we derive a massive star formation rate in the disk of 60 solar masses/yr. (Author)