Infrared Emission from Clusters in the Star-forming Disk of Henize 2-10

Abstract

We have made subarcsecond-resolution images of the central 10'' of the Wolf-Rayet dwarf galaxy He 2-10 at 11.7 μm, using the Long Wavelength Spectrometer on the Keck I Telescope. The spatial distribution of the infrared emission roughly agrees with that of the rising spectrum radio sources seen by Kobulnicky & Johnson and confirms that those sources are compact H II regions, rather than supernova remnants or other objects. The infrared sources are more extended than the subarcsecond rising spectrum radio sources, although the entire complex is still less than 5'' in extent. On size scales of 1'' the infrared and radio emission are in excellent agreement, with each source requiring several hundred to a thousand O stars for excitation. The nebulae lie in a flattened disklike distribution about 240 by 100 pc and provide all of the flux measured by IRAS for the entire galaxy in the 12 μm band; 30% of the total IRAS flux from the galaxy emanates from one 15–30 pc source. In this galaxy, intense star formation, probably triggered by an accretion event, is confined to a central disk, which breaks up into distinct nebulae presumably marking the sites of young super–star clusters.