CO depletion in the starless cloud core L1544

Caselli, P.; Walmsley, C.M.; Tafalla, M.; Dore, L.; Meyers, P.C.

doi:10.1086/312280

CO depletion in the starless cloud core L1544

P. Caselli
(
- IRAM, St. Martin d'Heres
)
,
C.M. Walmsley
(
- IRAM, St. Martin d'Heres
)
,
M. Tafalla
(
- IRAM, St. Martin d'Heres
)
,
L. Dore
(
- IRAM, St. Martin d'Heres
)
,
P.C. Meyers
(
- IRAM, St. Martin d'Heres
)

1999

19 pages

Published in:

Astrophys.J.Lett. 523 (1999) L165

DOI:

10.1086/312280

Report number:

IRAM-522

View in:

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Abstract: (IOP)

We present evidence for CO depletion toward the starless cloud core L1544. A comparison between C17O and the 1.3 mm continuum dust emission shows that CO is depleted by a factor of ~10 at the dust peak. Our observations are consistent with a model in which CO is condensed out onto dust grains at densities abovend~ 105cm-3. The corresponding radius of the "depleted region" isrd~ 6500 AU, and we find that this depletion causes 2.3M☉of gas to be lost to view in molecular line emission. Optically thin high-density tracers, such as HC18O+and D13CO+, show double-peaked profiles which suggest that we are observing superposed emission from the foreground and background undepleted layers with density belownd. We conclude from our data that the core is probably young (~104yr old) and collapsing. For the component atVLSR= 7.1 km s-1in this line of sight, we estimate [DCO+]/[HCO+] = 0.12 ± 0.02, which is larger by a factor of order 2 than values derived in other dense cloud cores.

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