Inner Galaxy HII regions

We used the H110{alpha} line to establish the velocity of the HII regions and H_2_CO absorption lines to distinguish between near and far distances. We detected the H110{alpha} RRLs in 28 sources and H_2_CO absorption lines in 59 sources.

In the latter case, 43 features had not previously been observed. H_2_CO and H110{alpha} lines were simultaneously detected toward 23 HII regions. We resolved the kinematic distance ambiguities for 14 HII regions and 20 intervening molecular clouds.