SIMBAD references

1999ApJ...514..899H - Astrophys. J., 514, 899-908 (1999/April-1)

Ammonia absorption toward the ultracompact H II regions G45.12+0.13 and G45.47+0.05.


Abstract (from CDS):

We present observations of the 1.3 cm continuum and NH3(2,2) and (4,4) inversion lines toward the two ultracompact H II regions G45.12+0.13 and G45.47+0.05 with a resolution of about 3''. In G45.12+0.13 we find that the continuum emission from the ultracompact core is embedded in a larger region with an extent of about 20''x10''. Compact absorption in the NH3(2,2) and (4,4) lines is detected against the bright continuum core. The ammonia data indicate Trot=78 K and N(NH3) = 1.4x1016 cm–2. The molecular gas traced by the NH3 absorption is blueshifted by about 5 km.s–1 with respect to the ionized gas and the bulk of the molecular gas in the region. Possibly the ammonia absorption traces the molecular gas at the base of an outflow which originates very close to the ultracompact H II region.

In the case of G45.47+0.05, we measure a deconvolved size of 1".5x0".8 for the region of 1.3 cm continuum emission. We detect extended emission in the NH3(2,2) line in the vicinity of the ionized gas. Compact absorption is detected in both the (2,2) and (4,4) line against the 1.3 cm continuum. The absorption line data indicate Trot=59 K and N(NH3)=1.8x1017 cm–2. The ammonia absorption occurs at a velocity redshifted by about 3.5 km.s–1 with respect to the emission. This supports the hypothesis of a remnant infalling molecular core onto the ultracompact H II region.

Abstract Copyright:

Journal keyword(s): ISM: H II Regions - ISM: individual (G45.12+0.13, G45.47+0.05) - ISM: Molecules - Stars: Formation

Simbad objects: 5

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