Minchin, Nigel R.; White, Glenn J. and Padman, Rachael
A multitransitional molecular and atomic line study of S:140.
Astronomy and Astrophysics, 277 pp. 595–608.
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We present high-angular resolution maps of the S 140 molecular cloud in various transitions of the ¹²CO, ¹³CO and C18O molecules and single-channel observations of the ³P₁→H³P₀ line of neutral atomic carbon (CI). Velocity channel maps of the ¹²CO lines show a systematic shift of the emission peak away from the outflow source with increasing velocity offset from the line centre. The blue and redshifted outflow lobes are separated by ~35 arcsec (0.15 pc) in projection and the outflow axis is believed to be directed close to the observers' line-of-sight. The masses of the blue and redshifted outflow lobes were found to be 19.5 and 8.1M⊙ respectively, giving a total mass for the outflow of 27.6M⊙. The higher J-level 12CO lines are strongly self-absorbed, with the amount of self-absorption varying with position across the mapped region. All the ¹²CO, ¹³CO and C¹⁸O lines show enhanced main beam brightness temperatures at the molecular cloud/H II region interface. The ¹³CO line intensities imply the excitation temperature increases from ~65-70K at the position of the outflow source, to ~250K at the interface region. The CI emission is mainly confined to a clumpy, elongated ridge-like feature adjacent to the edge of the molecular cloud and is coincident with a similar feature seen in ¹²CO line emission. The coincidence of these features contradicts homogeneous cloud models and is interpreted as evidence that the molecular material is composed of dense clumps interspersed with a more tenuous interclump medium. A second region of intense CI emission is located inside a ring of CS emission, implying that ¹²CO here is dissociated by the radiation field from the embedded infrared cluster and not the external radiation field. Observed positions on the PDR have significantly higher values Of Tmb(CI)/Tmb(¹³CO) than for the general cloud, implying N(CI)IN(¹³CO) is likely to be significantly higher for positions on the PDR than in the general molecular cloud.
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