\font\rma=cmr8 \font\brmeight=cmbx8 \def\bhii H\/{\brmeight II} \ \def\hii{H{\rma\thinspace II}} \catcode\@=11 \def\gapprox{\mathrel{\mathpalette\@versim>}} \def\lapprox{\mathrel{\mathpalette\@versim<}} \def\@versim#1#2{\lower2.9truept\vbox{\baselineskip0pt\lineskip0.5truept \ialign{$\m@th#1\hfil##\hfil$\crcr#2\crcr\sim\crcr}}} \catcode\@=12 \def\pdeg {\ifmmode{.\kern-.25em ^{\circ}} \else{$.\kern-.25em ^{\circ}$} \fi}
IRAS PROPERTIES OF \bhii \ REGIONS
Session 60 -- HII Regions
Display presentation, Thursday, 9:20-4:00, Pauley Room

## [60.04] IRAS PROPERTIES OF \bhii \ REGIONS

T.A. Kuchar (Phillips Lab/GPOB)

The infrared emission for a set of 70 \hii \ regions, with known kinematic distances, was examined using images from the {\sl IRAS\/} Sky Survey Atlas. These are radio bright ($f_{\rm 4860MHz} >$ 1 Jy) \hii \ regions located in the first Galactic quadrant: $30\deg \lapprox \ell \lapprox 60\deg , \mid b\mid \lapprox 0\pdeg5$. The `typical' \hii\ region in this sample has a dust temperature $T(60/100) = 32$K (for $\lambda^{-2}$ emissivity law), a diameter of 30 pc, and a luminosity ($\lambda \ge 50\mu$m) of $10^5-10^6 L_{\sun}$. However, there are several noticeable exceptions which are associated with the molecular ring and the W43 and W51 \hii\ region complexes. These \hii\ regions are hotter than average and appear brighter than average at all {\sl IRAS\/} wavebands. It is interesting to note that the \hii\ regions associated with the W49 complex have characteristics typical of the sample.

{\sl IRAS\/} LRS data were available for 24 of the sample \hii\ regions. The shapes of the spectra fell into two distinct classes based on the red ($\lambda \gapprox 12\mu$m) end of the spectrum: flat or rising continua. Some of these spectra also showed silicate absorption at $10\mu$m. All of these spectra are continuum dominated and show emission lines of [Ne{\rma II}], [Ne{\rma III}], or [S{\rma III}]. Most of these lines are detected above the 3$\sigma$ threshold, however some of them are only at the 2$\sigma$ level. Also some of the spectra show an unidentified emission line at $21\mu$m. The presence of the emission lines appear uncorrelated with any of the other {\sl IRAS\/} properties. This suggests that the emission from the ionized gas may be spatially distinct from the dust emission.