Astronomy and Astrophysics – Astronomy
Scientific paper
Mar 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995aas...186.3601o&link_type=abstract
American Astronomical Society, 186th AAS Meeting, #36.01; Bulletin of the American Astronomical Society, Vol. 27, p.862
Astronomy and Astrophysics
Astronomy
Scientific paper
We have used the IRAM 30-m telescope and the Plateau de Bure Interferometer (PdBI), to map the star--forming regions surrounding the two ultracompact H{sc ii} regions G10.47+0.03 and G31.41+0.31. The J=6--5, J=8--7, and J=12--11 rotational transitions of methyl cyanide (CH_3CN), its isotopomer (13) CH_3CN, and of vibrationally excited v_8=1 CH_3CN, were observed with the 30-m. With the PdBI, we produced maps of CH_3CN(6--5), CH_3(13) CN(6--5), vibrationally excited v_8=1 CH_3CN(6--5), and of the 3 mm continuum emission. Temperatures and column densities for the two sources were determined from the 30-m data, on the basis of the intensities of the optically thin lines, as well as employing the optically thick lines. From the single--dish data we also infer the existence of an extended envelope (>= 10''), not detectable with the interferometer, and the velocity shift in G31.41+0.31 (see below) is detected. Our data suggest that in this source there are =~ 2200 solar masses within a radius <0.1 pc. An abundance ratio [CH_3CN]/[NH_3] of order of 210(-3) is also found in both objects. From the PdBI data, and in the case of G31.41+0.31, the core angular diameter as measured in both methyl cyanide and the 3 mm continuum is =~ 1'', corresponding to =~ 0.04 pc. G10.47+0.03 is basically unresolved in our maps. Velocity gradients are found in both sources, the most evident beeing in G31.41+0.31, where we observe ~ 400 km s(-1) pc^{-1}$ in the SW--NE direction. Therefore, these hot--cores are sites of high velocity motions. We also discuss the 3 mm continuum emission, which is likely to come mostly from heated dust in the case of G31.41+0.31, whereas in G10.47+0.03 contributions from both free--free and dust emission are likely to be observed. We discuss possible scenarios for these two sources.
Cesaroni Riccardo
Olmi Luca
Walmsley Charles Malcolm
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