A Study of the Physics and Chemistry of L134N

Dickens, J. E.; Irvine, William M.; Snell, R. L.; Bergin, Edwin A.; Schloerb, F. P.; Pratap, Preethi; Miralles, M. P.

doi:10.1086/317040

Cited by 123 publications

(150 citation statements)

References 55 publications

Supporting

Mentioning

131

Contrasting

Order By: Relevance

“…The abundances relative to H 2 are directly deduced from line intensities (assuming local thermodynamic equilibrium conditions, LTE) and the HCN and HNC abundances are deduced from 13 C isotopomers abundance using a 12 C/ 13 C ratio equal to 65. The observations of (Dickens et al 2000) also use H 13 CN and HN 13 C as a proxy and they compute the abundances from line intensities using a statistical equilibrium model using the same collisional rates for HNC and HCN, which is known to lead to an overestimation of HNC abundances (Sarrasin et al 2010, Dumouchel et al 2010, Dumouchel et al 2011. (Dickens et al 2000) found higher HCN and HNC densities attributing their differences with (Swade 1989) to the optical depth estimation as Swade assumed optically thin emission, potentially underestimating the column densities.…”

Section: Comparison With Observationsmentioning

confidence: 99%

The interstellar gas-phase chemistry of HCN and HNC

Loison¹,

Wakelam²,

Hickson³

2014

Monthly Notices of the Royal Astronomical Society

107

109

View full text Add to dashboard Cite

+ CH 2 reaction and two new reactions: H + CCN and C + HNC. We test the effect of the new rate constants and branching ratios on the predictions of gas-grain chemical models for dark cloud conditions. The rapid C + HNC reaction keeps the HCN/HNC ratio significantly above one as long as the carbon atom abundance remains high. However, the reaction of HCN with H 3 + followed by DR of HCNH + acts to isomerize HCN into HNC when carbon atoms and CO are depleted leading to a HCN/HNC ratio close to or slightly greater than 1. This agrees well with observations in TMC-1 and L134N taking into consideration the overestimation of HNC abundances through the use of the same rotational excitation rate constants for HNC as for HCN in many radiative transfer models.

show abstract

Section: Comparison With Observationsmentioning

confidence: 99%

The interstellar gas-phase chemistry of HCN and HNC

Loison¹,

Wakelam²,

Hickson³

2014

Monthly Notices of the Royal Astronomical Society

107

109

View full text Add to dashboard Cite

show abstract

“…Studies of chemical evolution have been made up to now with single-dish observations using several transitions of selected early-and late-time molecules, usually CS, N 2 H + , NH 3 , HCO + , SO, SO 2 , and HC 3 N. These studies of starless cores show maps where emission seems to originate in several clumps distributed all over the region (Dickens et al 2000) or in round-like clumps (Tafalla et al 2002). All these studies show evidences of chemical differentiation.…”

Section: Comparison With Other Studiesmentioning

confidence: 99%

Multitransitional observations of the CS core of L673

Morata

Girart

Estalella

2002

A&A

View full text Add to dashboard Cite

Abstract.A multitransitional study with the BIMA interferometric array was carried out toward the starless core found in the L673 region, in order to study the small-size structure of the cores detected with previous single-dish observations, which provides us with a test of the predictions of the chemical model of Taylor et al. (1996Taylor et al. ( , 1998. We detected emission in the CS (J = 2 → 1), N 2 H + (J = 1 → 0), and HCO + (J = 1 → 0) lines. Several clumps of size < ∼ 0.08 pc were found for each line distributed all over the region where previous single-dish emission was found (Morata et al. 1997). Each molecular transition traces differently the clump distribution, although in some cases the detected clumps are coincident. The distribution of the N 2 H + emission and the single-dish NH 3 emission are coincident and compatible with an origin in the same gas. The large fraction of missing flux measured for the CS (2 → 1) transition can be explained if the cloud is formed by a clumpy and heterogeneous medium. Four positions were selected to derive the abundance ratios [N 2 H + /CS] and [HCO + /CS] from the molecular column density determinations, and to compare them with the values predicted by the chemical model. The model was able to explain the interferometric observations, and, in particular, the chemical differentiation of the detected clumps and the coincidence of the NH 3 and N 2 H + emissions. The lack of HCO + towards the two selected positions that trace the more evolved clumps cannot be accounted for by the model, but it is possibly due to strong self-absorption. We propose a classification of the studied clumps according to the stage of chemical evolution indicated by the molecular abundances.

show abstract

“…The sample for the low mass star forming molecular clouds is: IRAS 16293 , NGC 1333 IRAS4A , the Serpens S68 (McMullin et al 2000), 05338-0624 (McMullin et al 1994) and several other regions for H2CO (Dickens & Irvine 1999) and CH3OH (Kalenskii & Sobolev 1994). The sample for the quiescent dark molecular clouds is: OMC-1N , TMC-1 (Pratap et al 1997), L134N (Dickens et al 2000), and the CB clouds for H2CO (Turner 1994). the typical values found in the molecular clouds.…”

Section: Chemical Comparison With Other Dense Molecular Regionsmentioning

confidence: 99%

The molecular condensations ahead of Herbig-Haro objects

Girart

Viti

Williams

et al. 2002

A&A

View full text Add to dashboard Cite

Abstract. We present a CSO and BIMA molecular line survey of the dense, quiescent molecular environment ahead of HH 2. The molecular gas is cold, 13 K, and moderately dense, 3 ×10 5 cm −3 . A total of 14 species has been detected (including different isotopes and deuterated species). The relative abundances of the clump are compared with other dense molecular environments, including quiescent dark clouds, and active low and high mass star forming regions. This comparison confirms the peculiar chemical composition of the quiescent gas irradiated by the HH objects. Thus, from this comparison, we found that the HCO + , CH3OH and H2CO are strongly enhanced. SO and SO2 are weakly enhanced, whereas HCN and CS are underabundant. The CN abundance is within the range of values found in starless dark clouds, but it is low with respect to high mass star forming regions. Finally, the chemical composition of HH 2 confirms the qualitative results of the Viti & Williams (1999) complex chemical model that follows the chemical behavior of a molecular clump irradiated by a HH object.

show abstract

A Study of the Physics and Chemistry of L134N

Cited by 123 publications

References 55 publications

The interstellar gas-phase chemistry of HCN and HNC

The interstellar gas-phase chemistry of HCN and HNC

Multitransitional observations of the CS core of L673

The molecular condensations ahead of Herbig-Haro objects

Contact Info

Product

Resources

About