Astronomy and Astrophysics – Astronomy
Scientific paper
Apr 1990
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1990a%26a...230l...5h&link_type=abstract
Astronomy and Astrophysics (ISSN 0004-6361), vol. 230, no. 1, April 1990, p. L5-L8.
Astronomy and Astrophysics
Astronomy
39
Active Galactic Nuclei, Astronomical Spectroscopy, Cosmochemistry, Interstellar Chemistry, Millimeter Waves, Molecular Spectra, Extragalactic Radio Sources, Infrared Sources (Astronomy), Spiral Galaxies
Scientific paper
The detection of CN, CS, C2H, HCN, HNC, NCO(+), and CH3OH is reported from the nucleus of NGC 4945, one of the extragalactic sources with the richest molecular spectrum. For the J = 10-9 line of HC3N, an upper line temperature limit of T(A) = 12 mK is obtained. There are two kinds of line shapes: some have a main peak at about 450 km/s, a shoulder at 500-550 km/s, and a narrow secondary peak at about 700 km/s (e.g., HCN); others are flat topped (e.g., HNC). Two alternative interpretations are suggested to explain the spectral line shapes: the first is based on different opacities, the second on two spatially separated emission regions. A comparison of CO, CS, and CH3OH data from the most prominent extragalactic molecular sources shows that there are differences in relative abundances. It is suggested that this may be due to chemical processes, operating over linear scales of a few 100 pc.
Harju Jorma
Henkel Carsten
Nyman L.-AA.
Whiteoak John B.
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