SIMBAD references

1999ApJ...519..244M - Astrophys. J., 519, 244-256 (1999/July-1)

VLBA observations of 12 GHz methanol masers toward W3(OH).


Abstract (from CDS):

We have conducted VLBA observations of the 12 GHz CH3OH masers toward the ultracompact H II region W3(OH). The angular resolution of ~1 mas is sufficient to resolve most of the maser spots and determine their sizes and brightness temperatures. The FWHM sizes of the spots are found from ≤2 to 10 AU with brightness temperatures between 109 and 6x1011 K. The actual brightness temperatures may be higher (by a factor ≤10) than the measured values, because most of the spots have spectral profiles unresolved with our velocity resolution (0.28 km.s–1). Our data also suggest the presence ofa spatially extended component of maser emission with size ≥20 mas and brightness temperature≤109 K.

The comparison of our data with previous 6.7 GHz VLBI observations shows that there is a good spatial (≤10 mas) and velocity (within 0.3 km.s–1) correspondence between numerous 12 and 6.7 GHz CH3OH spots. Comparing our maps with those of Menten et al. yields relative proper motions of a few km.s–1 in magnitude. A ``linear structure'' of approximately 200 AU in size (P.A.=141°) is found in the northern methanol maser clump, which also shows a regular trend of radial velocities with projected positions (a velocity gradient of 2400 km.s–1.pc–1).

Abstract Copyright:

Journal keyword(s): ISM: H II Regions - ISM: Individual: Alphanumeric: W3 - ISM: molecules - Masers - radio lines: ISM - stars: formation

Nomenclature: Table 2: MMWR NNa (Nos 1-48), N=51.

Simbad objects: 16

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