WARM MOLECULAR GAS ASSOCIATED WITH COMETARY H-II REGIONS

We present observations of the (J, K)=(2, 2) and (3, 3) inversion tran sitions of ammonia, made at similar to 4'' resolution with the VLA, in the direction of the G32.80+0.19 and G61.48+0.09 star-forming regions , which contain cometary-like and compact H II regions. Our data revea l the presence, in both complexes, of compact ammonia structures, with sizes of similar to 0.2 pc, which are intimately associated with the regions of ionized gas. The ammonia clumps have excitation temperature s in the range 60-80 K and molecular hydrogen densities in the range ( 0.7-5) x 10(4) cm(-3). We suggest that these warm ammonia clumps corre spond to compact molecular structures, embedded within more extended m olecular clouds, which have been heated by the radiation from the star that ionizes the associated H II region and possibly compressed by th e shocks driven by the expansion of the H II region. We find that the molecular clumps associated with the cometary-like H II regions are lo cated near the head of the ionized region and have line-center velocit ies similar to those of the ionized gas at the head position. These re sults imply that the cometary H II regions studied here, which exhibit strong gradients in the line-center velocities along their symmetry a xis, are experiencing the champagne phase of evolution. In particular, the case of G61.48-0.09 is interesting because it seems that two cham pagne flows are occurring in this H II region. The ammonia clump assoc iated with the most compact H II region within the G32.80+0.19 complex exhibits the (2, 2) main hyperfine (HF) line in absorption and the (3 , 3) main HF line in emission, which we explain as due to a blend, wit hin a synthesized beam, of an emitting region of hot molecular gas and an absorbing region of cold gas in front of a continuum source.