CO Depletion in the Starless Cloud Core L1544

Caselli, P.; Walmsley, C. M.; Tafalla, M.; Dore, Luca; Myers, Philip C.

doi:10.1086/312280

Cited by 492 publications

(590 citation statements)

References 27 publications

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“…This case is extremely unlikely as it requires typical densities of ∼10 6 cm −3 over a size of 20 (3200 AU). The depletion factor would also be a factor of ∼2 smaller if the central temperature is taken to be 11 K instead of 7.5 K. These results considerably extend the previous works on depletion in pre-stellar cores by Kramer et al (1999), Caselli et al (1999) and more recently by Tafalla et al (2002). The latter report similar depletion factors for L1544 and 4 other pre-stellar cores in the Taurus molecular cloud.…”

Section: Discussionsupporting

confidence: 85%

“…modified thermal balance or contraction by ambipolar diffusion induced by a decreased abundance of the molecule. CO depletion in dense cores has already been discussed by Kramer et al (1999), Willacy et al (1998), and Caselli et al (1999, 2002a, 2002b who focussed on L1544, a core similar to the ones we discuss in this work. Here, we studied the distribution and abundance of CO via its rarer isotopes C 17 O(1-0) and C 18 O(1-0), and of N 2 H + (1-0) in a sample of pre-stellar cores, using the 1.3 mm continuum as a tracer of the H 2 column density.…”

Section: Introductionsupporting

confidence: 79%

“…The core L1544, studied in detail by Caselli et al (1999Caselli et al ( , 2002aCaselli et al ( , 2002b, has also been included for comparison.…”

Section: Observations and Data Reductionmentioning

confidence: 99%

See 2 more Smart Citations

The degree of CO depletion in pre-stellar cores

Bacmann¹,

Leflóch²,

Ceccarelli³

et al. 2002

A&A

186

204

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Abstract. We present new results on CO depletion in a sample of nearby pre-stellar cores, based on observations of the millimeter C 17 O and C 18 O lines and the 1.3 mm dust emission with the IRAM 30 m telescope. In most cases, the distribution of CO is much flatter than that of the dust, whereas other tracers, like N2H + , still probe the latter. In the centre of these objects, we estimate CO to be underabundant by a factor 4-15 depending on the cores. The CO underabundance is more pronounced in the central regions and appears to decrease with increasing distance from the core centre. This underabundance is most likely due to the freezing out of CO onto the dust grains in the cold, dense parts of the cores. We find evidence for an increase of the CO depletion degree with the core density.

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Section: Discussionsupporting

confidence: 85%

Section: Introductionsupporting

confidence: 79%

See 1 more Smart Citation

The degree of CO depletion in pre-stellar cores

Bacmann¹,

Leflóch²,

Ceccarelli³

et al. 2002

A&A

186

204

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“…Such a structure in the low-mass protostars has already been inferred for several molecules like CO and H 2 CO Jørgensen et al 2004Jørgensen et al , 2005. The raising of the abundance in the outermost regions of the envelope is explained by a longer depletion timescale than the lifetime of the protostars (∼10 4 −10 5 years) for H 2 densities lower than ∼10 4 −10 5 cm −3 (e.g., Caselli et al 1999;Jørgensen et al 2004). On the other hand, Hollenbach et al (2009) have shown that, at the edge of molecular clouds, the icy mantles are photodesorbed by the UV photons, giving rise to an extended layer with a higher water abundance for a visual extinction A V ∼ 1-4 mag (for G 0 = 1).…”

Section: Determination Of the Hdo Abundancementioning

confidence: 55%

A study of deuterated water in the low-mass protostar IRAS 16293-2422

Coutens¹,

Vastel²,

Caux³

et al. 2012

A&A

133

236

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Context. Water is a primordial species in the emergence of life, and comets may have brought a large fraction to Earth to form the oceans. To understand the evolution of water from the first stages of star formation to the formation of planets and comets, the HDO/H 2 O ratio is a powerful diagnostic. Aims. Our aim is to determine precisely the abundance distribution of HDO towards the low-mass protostar IRAS 16293-2422 and learn more about the water formation mechanisms by determining the HDO/H 2 O abundance ratio. Results. It is the first time that so many HDO and H 182 O transitions have been detected towards the same source with high spectral resolution. We derive an inner HDO abundance (T ≥ 100 K) of about 1.7 × 10 −7 and an outer HDO abundance (T < 100 K) of about 8 × 10 −11 . To reproduce the HDO absorption lines observed at 894 and 465 GHz, it is necessary to add an absorbing layer in front of the envelope. It may correspond to a water-rich layer created by the photodesorption of the ices at the edges of the molecular cloud. At a 3σ uncertainty, the HDO/H 2 O ratio is 1.4-5.8% in the hot corino, whereas it is 0.2-2.2% in the outer envelope. It is estimated at ∼4.8% in the added absorbing layer. Conclusions. Although it is clearly higher than the cosmic D/H abundance, the HDO/H 2 O ratio remains lower than the D/H ratio derived for other deuterated molecules observed in the same source. The similarity of the ratios derived in the hot corino and in the added absorbing layer suggests that water formed before the gravitational collapse of the protostar, contrary to formaldehyde and methanol, which formed later once the CO molecules had depleted on the grains.

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“…In undepleted gas, reaction (9) represents a minor loss for H + 3 , however, as other species begin to freeze onto grain surfaces, reaction with HD becomes the dominant loss mechanism for H + 3 . As this produces H 2 D + , the This theoretical expectation, first predicted by Brown & Millar (1989), has recently been confirmed observationally by the detection of large [DCO + ]/[HCO + ] ratios in L1544 in clumps in which CO is significantly depleted (Caselli et al 1999). It may also prove important in explaining the large molecular D/H ratios observed towards IRAS 16293 and L134N.…”

Section: The Chemical Modelsmentioning

confidence: 70%

A survey of [HDCO]/[ H$_\mathsf{2}$CO] and [DCN]/[HCN] ratios towards low-mass protostellar cores

Roberts

Fuller

Millar

et al. 2002

A&A

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. We compare our results with predictions from detailed, chemical models, and to other observations made in these sources. We find best agreement between models and observations by assuming that interaction between gas phase molecules and dust grains has impacted on the chemistry during the cold pre-collapse phase of the cloud's history. The abundance of deuterated species indicates that the dense gas out of which a low mass protostar forms, evolves and collapses on a timescale of ≤50 000 years. We find no marked difference between molecular D/H ratios towards different regions, or between Class 0 and Class I protostars. However, the striking difference between the [DCN]/[HCN] ratios we have measured and those previously observed towards Hot Molecular Cores leads us to suggest that there are significant evolutionary differences between high and low mass star forming regions.

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CO Depletion in the Starless Cloud Core L1544

Cited by 492 publications

References 27 publications

The degree of CO depletion in pre-stellar cores

The degree of CO depletion in pre-stellar cores

A study of deuterated water in the low-mass protostar IRAS 16293-2422

A survey of [HDCO]/[ H$_\mathsf{2}$CO] and [DCN]/[HCN] ratios towards low-mass protostellar cores

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