EMISSION LINE OBSERVATIONS OF H II REGIONS

J. H. Lacy
1981 Symposium - International astronomical union  
Optical observations provide a wealth of information on atomic abundances, the excitation (level of ionization), the kinetic temperature, and the density of the gas in H II regions. However, obscuration by dust limits optical observations of galactic H II regions to those which are nearby (within a few kpc) and which are unobscured by the molecular clouds out of which they are formed (and so generally evolved). Radio observations are unhampered by extinction but provide much more limited
more » ... tion. The abundance of H+, He+and occasionally C+can be determined as well as the kinetic temperature of the gas, but no direct information on the abundance of other species or the excitation is available.
doi:10.1017/s0074180900075239 fatcat:owszi3cjvreqldhfz4n5lckr7q