Astron. Astrophys. 355, 1115-1121 (2000)

5. Summary and conclusion

In this paper we present NH₃(1,1) line observations in 108 southern hemisphere HII regions. The main results of this research are: (1) ammonia was detected in about 30 % of the observed positions, (2) no ammonia (1,1) line was identified above the three times the antenna temperature limit of 0.04 K in the - galactic longitude interval, where 14 HII regions were observed, (3) ammonia was detected in about 60 % of the positions which had an associated IRAS point source with color index of ultra-compact HII regions, (4) it was found a gradient of about -0.08 in the fraction of NH₃ sources in the direction of HII regions, per kpc in galactocentric radius. and (5) the distribution of ammonia sources varies as , indicating, under certain assumptions, that the fraction of molecular clouds associated to HII regions decrease as the H₂ column density increases.

© European Southern Observatory (ESO) 2000

Online publication: March 21, 2000
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