Observations of “Hot Cores”

Ohishi, Masatoshi

doi:10.1017/s0074180900009244

Cited by 14 publications

(11 citation statements)

References 30 publications

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“…These are the strongest sources in our sample and have kinetic temperatures higher than the group II sources. All of them, except G30.8-0.1, are well-known hot cores (Wink et al 1984;Ohishi 1996).…”

Section: Discussionmentioning

confidence: 99%

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Determination of molecular gas properties using methyl cyanide lines

et al. 2000

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A survey of 27 galactic star-forming regions in the 6 K −5 K , 5 K − 4 K , and 8 K − 7 K CH 3 CN lines at 110, 92, and 147 GHz, respectively, was made. Twenty-five sources were detected at 110 GHz, nineteen at 92 GHz, and three at 147 GHz. The strongest CH 3 CN emission arise in hot cores in the regions of massive star formation. CH 3 CN abundance in these objects is larger than 10 −9 due to grain mantle evaporation. Weaker CH 3 CN lines were found in a number of sources. They may arise either in warm (30-50 K) dense (10 5 -10 7 cm −3 ) clouds, or in hot regions accompanied by colder gas.

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Section: Discussionmentioning

confidence: 99%

“…G34.26+0.15. An interferometer map of this well-known hot core (Ohishi 1996) in the 6 K − 5 K CH 3 CN lines have been already obtained by Akeson & Carlstrom (1996). The ratios of all the observed by us line intensities toward this source could not be fitted by homogeneous source models, suggesting a core-halo structure.…”

Section: Comments On Selected Sourcesmentioning

confidence: 91%

Determination of molecular gas properties using methyl cyanide lines

et al. 2000

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“…Cesaroni et al (1994) conclude that the H 2 O − NH 3 clumps are likely to be the site of massive star formation. Methyl cyanide seems to trace the same high density clumps (Olmi et al 1993(Olmi et al , 1996(Olmi et al , 1996b and one concludes that these are examples of the "hot core" phenomenon, where the presence of a nearby luminous star causes the evaporation of dust grain ice mantles in the surrounding medium and consequently enhances the abundance of several molecular species (see Millar 1997 andOhishi 1997).…”

Section: Introductionmentioning

confidence: 87%

High density molecular clumps around protostellar candidates

Cesaroni

Felli

Walmsley

1999

Astron. Astrophys. Suppl. Ser.

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Abstract. There are several indications that strong H 2 O maser emission arises at the very beginning of the evolution of a massive star and disappears when an Hii region becomes detectable in the radio continuum. If this is the case, one expects to find dense hot molecular gas surrounding embedded far IR sources coincident with H 2 O masers. In order to test this hypothesis, we have used the Pico Veleta 30-m radiotelescope to search for molecular line emission towards a sample of 12 H 2 O masers located in regions of massive star formation, but not directly associated with bright compact radio Hii regions, with the intention to identify the sites of newly born massive (proto)stars in their earliest stages and to study their properties.Our main goals were: a) to confirm the hypothesis that the H 2 O masers not associated with compact radio continuum emission are indeed located at the centre of high density clumps within a molecular cloud; b) to use several molecular transitions (namely:13 CO(2−1), CS(3−2), C 34 S(2−1), C 34 S(3−2), C 34 S(5−4), HCN(1−0), CH 3 CN(8−7), CH 3 CN(12−11), HCO + (1−0), CH 3 OH(3−2), CH 3 OH(5−4)) in order to derive information on the size, kinematics, temperature, density, and ionisation degree of the molecular gas in the places where star formation has just begun, as well as to search for the presence of outflows on scale sizes of 10 − 30 .In this paper we present the large amount of data obtained at Pico Veleta in a compressed way, but still sufficiently ample to give usable informations for further studies. General results from a first analysis of the data are also presented.Our first goal is amply verified since in all cases and in molecules tracing high density gas we find a barely resolved peak at the position of the maser, confirming the validity of our selection criteria. Our sample thus provides a valid reference list of regions of massive star formation in their earliest phases.As far as the second goal is concerned, the large variety of intensity ratios of different molecules, as well as of other Send offprint requests to: R. Cesaroni (cesa@arcetri.astro.it) derived parameters, point out that the molecular clumps where star formation is taking place are far from identical and that chemical evolution and influence of the newborn star may amply affect the line intensity ratios.In some cases small scale (seconds of arc) outflows were detected, not necessarily related to the minute of arc scale outflows present in the same regions.More detailed studies of each region are presented in separate papers.

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“…Many oxygen-bearing species, including alcohols, ethers, carboxylic acids, and aldehydes, have been discovered in the interstellar medium, 4 and many similar species are predicted to exist in detectable amounts. 5 Methanediol is one of these species, suspected to form in grain surface reactions triggered by the UV or cosmic ray processing of ice mantles.…”

Section: Introductionmentioning

confidence: 99%

A theoretical study of the conversion of gas phase methanediol to formaldehyde

Kent

Widicus

Blake

et al. 2003

The Journal of Chemical Physics

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Methanediol, or methylene glycol, is a product of the liquid phase reaction of water and formaldehyde and is a predicted interstellar grain surface species. Detection of this molecule in a hot core environment would advance the understanding of complex organic chemistry in the interstellar medium, but its laboratory spectroscopic characterization is a prerequisite for such observational searches. This theoretical study investigates the unimolecular decomposition of methanediol, specifically the thermodynamic and kinetic stability of the molecule under typical laboratory and interstellar conditions. Methanediol was found to be thermodynamically stable at temperatures of Ͻ100 K, which is the characteristic temperature range for interstellar grain mantles. The infinite-pressure RRKM unimolecular decomposition rate was found to be Ͻ10 Ϫ18 s Ϫ1 at 300 K, indicating gas phase kinetic stability for typical laboratory and hot core temperatures. Therefore, both laboratory studies of and observational searches for this molecule should be feasible.

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Observations of “Hot Cores”

Cited by 14 publications

References 30 publications

Determination of molecular gas properties using methyl cyanide lines

Determination of molecular gas properties using methyl cyanide lines

High density molecular clumps around protostellar candidates

A theoretical study of the conversion of gas phase methanediol to formaldehyde

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