Warm Carbon-Chain Chemistry

Sakai, Nami; Yamamoto, Satoshi

doi:10.1021/cr4001308

Cited by 162 publications

(184 citation statements)

References 220 publications

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“…They are characterised by comparably high abundances of long carbon-chain molecules such as HC 3 N, C 4 H, and C 6 H, and at the same time by low or moderate abundances of complex organic species. The difference between the chemical properties observed towards hot corinos and WCCC sources could be an effect of different collapse timescales (Sakai et al 2009b;Sakai & Yamamoto 2013). This mechanism has been verified by chemical modelling (Hassel et al 2008).…”

Section: Introductionmentioning

confidence: 64%

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Probing the effects of external irradiation on low-mass protostars through unbiased line surveys

Lindberg

Jørgensen

Watanabe

et al. 2015

A&A

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Context. The envelopes of molecular gas around embedded low-mass protostars show different chemistries, which can be used to trace their formation history and physical conditions. The excitation conditions of some molecular species can also be used to trace these physical conditions, making it possible to constrain for instance sources of heating and excitation. Aims. We study the range of influence of an intermediate-mass Herbig Be protostar. We also study the effect of feedback from the environment on the chemical and physical properties of embedded protostars. Methods. We followed up on an earlier line survey of the Class 0/I source R CrA IRS7B in the 0.8 mm window with an unbiased line survey of the same source in the 1.3 mm window using the Atacama Pathfinder Experiment (APEX) telescope. We also studied the excitation of the key species H 2 CO, CH 3 OH, and c-C 3 H 2 in a complete sample of the 18 embedded protostars in the Corona Australis star-forming region. Radiative transfer models were employed to establish abundances of the molecular species. Results. We detect line emission from 20 molecular species (32 including isotopologues) in the two surveys. The most complex species detected are CH 3 OH, CH 3 CCH, CH 3 CHO, and CH 3 CN (the latter two are only tentatively detected). CH 3 CN and several other complex organic molecules are significantly under-abundant in comparison with what is found towards hot corino protostars. The H 2 CO rotational temperatures of the sources in the region decrease with the distance to the Herbig Be star R CrA, whereas the c-C 3 H 2 temperatures remain constant across the star-forming region. Conclusions. The high H 2 CO temperatures observed towards objects close to R CrA suggest that this star has a sphere of influence of several 10 000 AU in which it increases the temperature of the molecular gas to 30-50 K through irradiation. The chemistry in the IRS7B envelope differs significantly from many other embedded protostars, which could be an effect of the external irradiation from R CrA.

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Section: Introductionmentioning

confidence: 64%

“…IRAS 16293-2422Schöier et al 2002;Cazaux et al 2003). (b) Sakai & Yamamoto (2013) and references therein. Observations were performed with several different single-dish telescopes with beam sizes between 10 and 30 .…”

Section: Rotational Diagramsmentioning

confidence: 99%

Probing the effects of external irradiation on low-mass protostars through unbiased line surveys

Lindberg

Jørgensen

Watanabe

et al. 2015

A&A

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“…1). Based on our observations, we conclude that CCC can also be present in slowly contracting clouds such as L1544 (Keto et al 2015) and that the C atoms driving the CCC can partially deplete on dust grain surfaces, producing solid CH 4 , which is the origin of the so-called warm carbon-chain chemistry (WCCC; Sakai & Yamamoto 2013), when it is evaporated in the proximity of newly born young stellar objects. This apparently contradicts the suggestion that WCCC becomes active when the parent core experiences a fast contraction on a timescale close to that of free fall (Sakai et al 2008(Sakai et al , 2009.…”

Section: Carbon-chain Chemistrymentioning

confidence: 74%

“…This apparently contradicts the suggestion that WCCC becomes active when the parent core experiences a fast contraction on a timescale close to that of free fall (Sakai et al 2008(Sakai et al , 2009. In these previous papers, fast contraction was invoked to allow C atoms to deplete onto dust grains before they are converted to CO in the gas phase (Sakai &Yamamoto 2013), so that a substantial amount of solid CH 4 is produced.…”

Section: Carbon-chain Chemistrymentioning

confidence: 92%

Chemical differentiation in a prestellar core traces non-uniform illumination

Spezzano

Bizzocchi

Caselli

et al. 2016

A&A

114

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Dense cloud cores present chemical differentiation because C-and N-bearing molecules are distributed differently, the latter being less affected by freeze-out onto dust grains. In this letter we show that two C-bearing molecules, CH 3 OH and c-C 3 H 2 , present a strikingly different (complementary) morphology while showing the same kinematics towards the prestellar core L1544. After comparing their distribution with the large-scale H 2 column density N(H 2 ) map from the Herschel satellite, we find that these two molecules trace different environmental conditions in the surrounding of L1544: the c-C 3 H 2 distribution peaks close to the southern part of the core, where the surrounding molecular cloud has an N(H 2 ) sharp edge, while CH 3 OH mainly traces the northern part of the core, where N(H 2 ) presents a shallower tail. We conclude that this is evidence of chemical differentiation driven by different amounts of illumination from the interstellar radiation field: in the south, photochemistry maintains more C atoms in the gas phase, allowing carbon-chain (such as c-C 3 H 2 ) production; in the north, C is mainly locked in CO, and methanol traces the zone where CO starts to freeze out significantly. During the process of cloud contraction, different gas and ice compositions are thus expected to mix towards the central regions of the core, where a potential solar-type system will form. An alternative view on carbon-chain chemistry in star-forming regions is also provided.

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“…It is also known as a prototypical warm-carbon-chain-chemistry source (Sakai et al 2008(Sakai et al , 2010Sakai & Yamamoto 2013). This source has a flattened infalling envelope with an edge-on configuration extending from north to south.…”

Section: Introductionmentioning

confidence: 99%

Geometric and Kinematic Structure of the Outflow/Envelope System of L1527 Revealed by Subarcsecond-Resolution Observation of Cs

Oya

Sakai

Leflóch

et al. 2015

ApJ

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Subarcsecond-resolution images of the rotational line emissions of CS and c-C 3 H 2 obtained toward the low-mass protostar IRAS 04368+2557 in L1527 with the Atacama Large Millimeter/submillimeter Array are investigated to constrain the orientation of the outflow/envelope system. The distribution of CS consists of an envelope component extending from north to south and a faint butterfly shaped outflow component. The kinematic structure of the envelope is well reproduced by a simple ballistic model of an infalling rotating envelope. Although the envelope has a nearly edge-on configuration, we find that the western side of the envelope faces the observer. This configuration is opposite to the direction of the large-scale (∼10 4 AU) outflow suggested previously from the 12 CO (J = 3-2) observation, and to the morphology of infrared reflection near the protostar (∼200 AU). The latter discrepancy could originate from high extinction by the outflow cavity of the western side, or may indicate that the outflow axis is not parallel to the rotation axis of the envelope. Position-velocity diagrams show the accelerated outflow cavity wall, and its kinematic structure in the 2000 AU scale is explained by a standard parabolic model with the inclination angle derived from the analysis of the envelope. The different orientation of the outflow between the small and large scale implies a possibility of precession of the outflow axis. The shape and the velocity of the outflow in the vicinity of the protostar are compared with those of other protostars.

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Warm Carbon-Chain Chemistry

Cited by 162 publications

References 220 publications

Probing the effects of external irradiation on low-mass protostars through unbiased line surveys

Probing the effects of external irradiation on low-mass protostars through unbiased line surveys

Chemical differentiation in a prestellar core traces non-uniform illumination

Geometric and Kinematic Structure of the Outflow/Envelope System of L1527 Revealed by Subarcsecond-Resolution Observation of Cs

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