Untangling compact and diffuse ionized emission toward galactic hii regions

HII regions are clouds of ionized hydrogen gas surrounding B0- and O-type stars. The ionized hydrogen in these regions emits both radio recombination line (RRL) and also thermal radio continuum. Diffuse ionized hydrogen, known as the \u27Warm Ionized Medium\u27 (WIM) also exists in the Galaxy. The WIM also emits RRLs and thermal radio continuum. Previous observation of compact \hii regions found two RRL components for many sources, one from the \hii region and the others from the WIM. By observing off-target positions sampling only the diffuse emission, we discerned the correct source velocities for 93 out of 116 HII regions that have multiple RRL components. We assigned kinematic distances to these sources by analyzing hydrogen absorption spectra taken toward the sources. We found that 64% of our sources lie beyond the tangent point distance