Compact Infrared Sources Associated with Southern H II Regions

We have found bright, compact, infrared (1-25 sources associated with 11 galactic H ii regions. We present maps showing complex structure at 10 in five of these sources. The remaining ones are characterized by a small (<20") core of high surface brightness, with an extended ( 1') halo. RCW 57/IRS 1, an unresolved source exceptionally bright at 4.8 , may be a protostar; a similar object may be embedded in RCW 38/IRS 1. The 1-25 luminosity of the single-component source G298.2-0.3 is 2 >c 106 L0, the highest of any known H ii region. In one source we have been able to detect the exciting star (RCW 38/IRS 2). As is typical for H ii regions with infrared counterparts, the energy spectra from 1.2 to 20 are at least as steep as F oc and the observed flux longward of 3.5 is in excess, while that shortward of 2.2 M is deficient when compared with an extrapolation of the radio fluxes. The short-wavelength data show that most of the sources are more heavily reddened than would be expected from interstellar dust alone. For any given source the colors at all wavelengths do not vary significantly with position, implying that the dust which radiates in the 10-20 region is well mixed with the ionized gas. Also, we find for this dust a lower limit to the ratio M(H ii)/ M(dust), which, for a reasonable choice of physical parameters, is higher than the interstellar value. The optical depth of a 10- i absorption feature usually associated with silicates correlates with 7(H2CO) as determined from radio measurements but not with the visual extinction. We attribute the radio and 10- absorption features to cool dust and molecules in circumnebular neutral clouds. The dust in these clouds is probably responsible for the far-infrared radiation, as has been discussed by several authors. For most and possibly for all the H ii regions, the 1-25 flux can be accounted for by the absorption on dust grains of resonantly trapped La photons. We find no evidence that any of this dust markedly affects the ionization structure of the H ii regions. Subject headings: infrared sources - interstellar matter - nebulae