Other
Scientific paper
Dec 1991
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1991jkas...24..217c&link_type=abstract
Journal of the Korean Astronomical Society, vol. 24, no. 2, p. 217-271
Other
3
Scientific paper
We have observed dense core around young stellar objects, DR21, S140, Orion-KL, and L1551 using four millimeter-wave transitions of HC3N J = 4-3, J = 5-4, J = 10-9 and J = 12-11. The spatial distribution of HC3N emission closely resembles the morphology of the previous CS observations that trace high density gas. These observations reveal the existence of HC3N dense cores around central IR source, elliptical in shape and almost perpendicular to the CO bipolar outflow axis. Small differences can be explained by that HC3N molecular line is more optically thin and is seen to be more detailed structure in the neighborhood of central IR sources. In S140 and Orion-KL, massive (~10Mo), slowly rotating dense cores lie near at the central IR sources of bipolar outflows. The velocity channel maps of DR21 show that the bipolar outflow gas may have a correlation with the dense core of DR21. We analysed intensities of the four lines to derive physical conditions in dense core from two methods, LTE and LVG. The column density of HC3N, N(HC3N), between LTE and LVG calculations agree well with each other. The abundances of HC3N in each observing source have been estimated using the average values of n(H2) and N(HC3N) and assuming the size of dense core. The fractional HC3N abundances in massive dense cores of DR21, S140, and Orion-KL have a range of (2-7)*10E-10, while that of low mass dense core, L1551, has one order of magnitude greater value of 2*10E-9. This should be considered good agreement with the result my Morris et al.(1976). It may be considered that dense cores of DR21, S140, and Orion-KL may have almost same stage of chemical evolution, and their abundances have a small values relative to that of L1551. The column density N(HC3N) decreases with increasing distance from the densest part of the cloud, the central infrared source, and have the relation of N(HC3N) ~ R^(-alpha), where alpha has a range of 0.65 to 0.89. The values of n(H2) are not varied with increasing distance from the dense core, and have almost same values. Therefore, it is considered that the dense cores in these regions probably
Chung Hee Sok
Masaki Morimoto
Osamu Kameya
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