Modeling the Lukewarm Corino Phase: Is L1527 Unique?

Hassel, G. E.; Herbst, Eric; Garrod, R. T.

doi:10.1086/588185

Cited by 108 publications

(150 citation statements)

References 36 publications

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“…The first is an extended pseudo-time-dependent approach based on the gas-phase network used in the steady-state results reported in Marcelino et al (2009), while the second is a time-dependent, gas-grain approach (Hassel et al 2008). In the pseudo-timedependent approach, the physical conditions are homogeneous and time-independent while the chemical process is occurring.…”

Section: Discussionmentioning

confidence: 99%

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The puzzling behavior of HNCO isomers in molecular clouds

Marcelino

Brünken

Cernicharo

et al. 2010

A&A

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Context. Isocyanic acid (HNCO) has been observed in different physical environments in the interstellar medium (ISM) and in external galaxies. HNCO has several metastable isomers with a ground electronic singlet state: HOCN, HCNO, and HONC. The recent detection of fulminic acid (HCNO) in prestellar and protostellar cores and cyanic acid (HOCN) in warm molecular sources (e.g. hot cores) in the Galactic center proves that these species could also be common constituents of the ISM. Aims. To shed some light on the possible formation pathways of these species, we searched for HCNO in the sources where HOCN has been previously detected and vice versa. We have also included the low-mass protostar IRAS 16293-2422, where HNCO is found to be prominent. Methods. Using the new EMIR receivers at the IRAM 30-m telescope, we performed deep searches for three rotational transitions of HOCN and four of HCNO. Results. We report the detection of HOCN in four sources -three dense cores and the lukewarm corino L1527 -where HCNO has been previously observed. HOCN is tentatively detected toward the protostellar binary IRAS 16293-2422. However, HCNO has been detected neither in this source nor in the sources of the Galactic center where HOCN has been previously reported. The derived abundance ratios HCNO/HOCN are close to unity in quiescent clouds, while they are less than 0.01-0.1 in warm clouds. We attempt to explain these results by using both gas-phase and gas-grain chemical models.

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Section: Discussionmentioning

confidence: 99%

“…The asymptotic temperatures for a lukewarm corino (e.g. L1527), a warm envelope surrounding a hot core, and the hot core itself are 30 K, 50 K, and 200 K, respectively (Garrod & Herbst 2006;Hassel et al 2008). The H 2 densities in the three models are 10 6 , 10 5 , and 10 6 cm −3 , respectively.…”

Section: Gas-grain Modelmentioning

confidence: 98%

The puzzling behavior of HNCO isomers in molecular clouds

Marcelino

Brünken

Cernicharo

et al. 2010

A&A

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“…The physical conditions of the five benchmarking cases are summarized in Table 1 (see also Snow & McCall 2006;Hassel et al 2008). These are chosen to represent a realistic astrophysical object yet be relatively simple.…”

Section: Benchmarking Modelsmentioning

confidence: 99%

Chemistry in disks

Semenov

Hersant

Wakelam

et al. 2010

A&A

213

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Context. We describe and benchmark two sophisticated chemical models developed by the Heidelberg and Bordeaux astrochemistry groups. Aims. The main goal of this study is to elaborate on a few well-described tests for state-of-the-art astrochemical codes covering a range of physical conditions and chemical processes, in particular those aimed at constraining current and future interferometric observations of protoplanetary disks. Methods. We considered three physical models: a cold molecular cloud core, a hot core, and an outer region of a T Tauri disk. Our chemical network (for both models) is based on the original gas-phase osu_03_2008 ratefile and includes gas-grain interactions and a set of surface reactions for the H-, O-, C-, S-, and N-bearing molecules. The benchmarking was performed with the increasing complexity of the considered processes: (1) the pure gas-phase chemistry, (2) the gas-phase chemistry with accretion and desorption, and (3) the full gas-grain model with surface reactions. The chemical evolution is modeled within 10 9 years using atomic initial abundances with heavily depleted metals and hydrogen in its molecular form. Results. The time-dependent abundances calculated with the two chemical models are essentially the same for all considered physical cases and for all species, including the most complex polyatomic ions and organic molecules. This result, however, required a lot of effort to make all necessary details consistent through the model runs, e.g., definition of the gas particle density, density of grain surface sites, or the strength and shape of the UV radiation field. Conclusions. The reference models and the benchmark setup, along with the two chemical codes and resulting time-dependent abundances are made publicly available on the internet. This will facilitate and ease the development of other astrochemical models and provide nonspecialists with a detailed description of the model ingredients and requirements to analyze the cosmic chemistry as studied, e.g., by (sub-) millimeter observations of molecular lines.

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“…In this case agreement with observations is seen for abundances of ethanol and dimethyl ether though not for some other complex molecules. Hassel et al (2008) specifically model L1529, a "lukewarm" corino, which may be the prototype of a new class of such objects. Their analysis demonstrates that, at least in the case of L1529, there is some difficulty in establishing definitvely how a particular chemical state came to evolve and a number of scenarios are possible depending on the length of time the corino spent in each particular phase.…”

Section: Resultsmentioning

confidence: 99%

Complex molecule formation in grain mantles

Hall

Millar

2010

A&A

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Context. Complex molecules such as ethanol and dimethyl ether have been observed in a number of hot molecular cores and hot corinos. Attempts to model the molecular formation process using gas phase only models have so far been unsuccessful. Aims. To demonstrate that grain surface processing is a viable mechanism for complex molecule formation in these environments. Methods. A variable environment parameter computer model has been constructed which includes both gas and surface chemistry. This is used to investigate a variety of cloud collapse scenarios.Results. Comparison between model results and observation shows that by combining grain surface processing with gas phase chemistry complex molecules can be produced in observed abundances in a number of core and corino scenarios. Differences in abundances are due to the initial atomic and molecular composition of the core/corino and varying collapse timescales. Conclusions. Grain surface processing, combined with variation of physical conditions, can be regarded as a viable method for the formation of complex molecules in the environment found in the vicinity of a hot core/corino and produce abundances comparable to those observed.

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Modeling the Lukewarm Corino Phase: Is L1527 Unique?

Cited by 108 publications

References 36 publications

The puzzling behavior of HNCO isomers in molecular clouds

The puzzling behavior of HNCO isomers in molecular clouds

Chemistry in disks

Complex molecule formation in grain mantles

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