The Infrared and Radio Fluxes Densities of Galactic HII Regions
  We derive infrared and radio flux densities of all ~1000 known Galactic HII
regions in the Galactic longitude range 17.5 < l < 65 degree. Our sample comes
from the Wide-Field Infrared Survey Explorer (WISE) catalog of Galactic \hii
regions \citep{anderson2014}. We compute flux densities at six wavelengths in
the infrared (GLIMPSE 8 microns, WISE 12 microns and 22 microns, MIPSGAL 24
microns, and Hi-GAL 70 microns and 160 microns) and two in the radio (MAGPIS 20
cm and VGPS 21 cm). All HII region infrared flux densities are strongly
correlated with their ~20 cm flux densities. All HII regions used here,
regardless of physical size or Galactocentric radius, have similar infrared to
radio flux density ratios and similar infrared colors, although the smallest
regions ($r<1\,$pc), have slightly elevated IR to radio ratios. The colors
$\log_{10}(F_{24 micron}/F_{12 micron}) \ge 0$ and $\log_{10}(F_{70
micron}/F_{12 micron}) \ge 1.2$, and $\log_{10}(F_{24 micron}/F_{12 micron})
\ge 0$ and $\log_{10}(F_{160 micron}/F_{70 micron}) \le 0.67$ reliably select
HII regions, independent of size. The infrared colors of ~22$\%$ of HII
regions, spanning a large range of physical sizes, satisfy the IRAS color
criteria of \citet{wood1989} for HII regions, after adjusting the criteria to
the wavelengths used here. Since these color criteria are commonly thought to
select only ultra-compact HII regions, this result indicates that the true
ultra-compact HII region population is uncertain. Comparing with a sample of IR
color indices from star-forming galaxies, HII regions show higher
$\log_{10}(F_{70 micron}/F_{12 micron})$ ratios. We find a weak trend of
decreasing infrared to ~20 cm flux density ratios with increasing $R_{gal}$, in
agreement with previous extragalactic results, possibly indicating a decreased
dust abundance in the outer Galaxy.
