Aperture Synthesis Observations of Molecular Gas in the Wolf-Rayet Galaxy He 2-10
Session 23 -- Starburst Activity in External Galaxies
Oral presentation, Monday, 30, 1994, 2:00-3:30

## [23.05] Aperture Synthesis Observations of Molecular Gas in the Wolf-Rayet Galaxy He 2-10

Chip Kobulnicky (University of Minnesota), Anneila Sargent (Caltech), Peter Conti (University of Colorado), David Hogg (NRAO), John Dickey (University of Minnesota)

We present aperture synthesis observations of the prototype Wolf-Rayet galaxy He 2-10 in the line of $^{12}$CO(1-0). These observations represent one of the first aperture synthesis maps of molecular gas in a blue compact dwarf galaxy. He 2-10 contains two starburst regions, A and B, separated by 8 arcsec which corresponds to 350 pc at at distance of 9 Mpc. Optical spectroscopy of region A indicates the presence of some 300 Wolf-Rayet and 4000 O-type stars, consistent with a very young starburst (Vacca \& Conti, 1992, ApJ 401, 543). From a line integral of of 165$\pm$8 K km s$^{-1}$ we derive a total molecular gas mass of $1.8 \times 10^8 M_\odot$ based on $^{12}$CO(1-0) spectra from the 12m NRAO telescope. The ratio of molecular to atomic gas mass, $M(H_2)/M(HI)$=0.54, is among the highest of any late type or blue compact dwarf galaxy.

$^{12}$CO(1-0) maps made with the Owens valley interferometer show two dynamical systems, suggesting an interaction-triggered starburst. While the CO peak is not conincident with either optical maximum, the CO is more nearly centered on the brighter and younger of the two starburst regions, A. There is no visible concentration of molecular gas near starburst region B which contains only a few hundred O-type stars. A significant fraction of the CO lies well outside the bright optical core, and is thus unaffiliated with the site of active star formation. We find a lower limit to the dynamical mass in the central 70 pc of $3.0\times 10^6 M_\odot$ inferred from the CO rotation curve. Conti \& Vacca (1994, ref) estimate the combined mass of nine blue starburst knots revealed by HST UV imaging to be $4.5\times 10^6 M_\odot$. Even if the inclination of He 2-10 is as low as 30$^\circ$, the young clusters, termed proto-globular clusters by Conti \& Vacca, comprise at least 75\% of the dynamical mass in the inner 70 pc!