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Astron. Astrophys. 349, L53-L56 (1999)

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Letter to the Editor

Evidence for inward motion in a galactic cirrus core

Andreas Heithausen

Radioastronomisches Institut der Universität Bonn, Auf dem Hügel 71, D-53121 Bonn, Germany (heith@astro.uni-bonn.de)

Received 9 August 1999 / Accepted 24 August 1999


Using the IRAM 30 m radiotelescope a dense core in MCLD 123.5+24.9 has been observed in the CS (J=2[FORMULA]1), (3[FORMULA]2) and (5[FORMULA]4) lines. In the lower two rotational lines the cloud extends over 0.03 pc [FORMULA] 0.15 pc at an adopted distance of 150 pc. The core harbours three dense condensations with full widths at half maximum between 4500 and 6100 AU. Based on C18O observations their masses are estimated to be between 0.06 and 0.12 [FORMULA]. The southernmost shows asymmetric self-absorbed CS (2[FORMULA]1) and (3[FORMULA]2) lines with the blue shifted part brighter than the red shifted; the velocity of the (5[FORMULA]4) transition is in between the blue and red shifted lines of the lower transitions. These features are well-tested diagnostics of inward motion in molecular clouds. An inward velocity of 4 to 10 m s-1 is estimated from the CS lines.

Key words: stars: formation – ISM: kinematics and dynamics – ISM: individual objects: MCLD 123.5+24.9 – ISM: molecules – radio lines: ISM

Present address: Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany

© European Southern Observatory (ESO) 1999

Online publication: September 2, 1999