Torsionally Excited Methyl Formate in Orion KL

Kobayashi, Kaori; Ogata, Kazumi; Tsunekawa, Shozo; Takano, Shuro

doi:10.1086/512977

Cited by 46 publications

(41 citation statements)

References 21 publications

(34 reference statements)

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“…8 of this work). High angular resolution also lowers the risk of spectral contamination by line-rich species such as C 2 H 5 CN, because the methyl formate distribution is different from that of N-bearing molecules ( Blake et al 1987;Kobayashi et al 2007;Friedel & Snyder 2008).…”

Section: Interest Of Methyl Formate Observationsmentioning

confidence: 99%

“…In this paper we investigate the spatial structure and temperature distribution of Orion-KL from observations of the O-bearing methyl formate (HCOOCH 3 ) molecule, which is relatively abundant in several interstellar hot cores and corinos, and especially abundant in Orion-KL (Blake et al 1987;Kobayashi et al 2007;Friedel & Snyder 2008). In Sect.…”

Section: Introductionmentioning

confidence: 99%

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HCOOCH₃as a probe of temperature and structure in Orion-KL

Favre

Despois

Brouillet

et al. 2011

A&A

100

238

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Context. The Orion Kleinmann-Low nebula (Orion-KL) is a complex region of star formation. Whereas its proximity allows studies on a scale of a few hundred AU, spectral confusion makes it difficult to identify molecules with low abundances. Aims. We studied an important oxygenated molecule, HCOOCH 3 , to characterize the physical conditions, temperature, and density of the different molecular source components. Methyl formate presents strong close rotational transitions covering a wide range of energy, and its emission in Orion-KL is not contaminated by the emission of N-bearing molecules. This study will help in the future 1) to constrain chemical models for the formation of methyl formate in gas phase or on grain mantles and 2) to search for more complex or prebiotic molecules. Methods. We used high-resolution observations from the IRAM Plateau de Bure Interferometer to reduce spectral confusion and to better isolate the molecular emission regions. We used twelve data sets with a spatial resolution down to 1.8 × 0.8 . Continuum emission was subtracted by selecting apparently line-free channels. Results. We identify 28 methyl formate emission peaks throughout the 50 field of observations. The two strongest peaks, named MF1 and MF2, are in the Compact Ridge and in the southwest of the Hot Core, respectively. From a comparison with single-dish observations, we estimate that we miss less than 15% of the flux and that spectral confusion is still prevailing as half of the expected transitions are blended over the region. Assuming that the transitions are thermalized, we derive the temperature at the five main emission peaks. At the MF1 position in the Compact Ridge we find a temperature of 80 K in a 1.8 × 0.8 beam size and 120 K on a larger scale (3.6 × 2.2 ), suggesting an external source of heating, whereas the temperature is about 130 K at the MF2 position on both scales. Transitions of methyl formate in its first torsionally excited state are detected as well, and the good agreement of the positions on the rotational diagrams between the ground state and the v t = 1 transitions suggests a similar temperature. The LSR velocity of the gas is between 7.5 and 8.0 km s −1 depending on the positions and column density peaks vary from 1.6 × 10 16 to 1.6 × 10 17 cm −2 . A second velocity component is observed around 9−10 km s −1 in a north-south structure stretching from the Compact Ridge up to the BN object, and this component is warmer at the MF1 peak. The two other C 2 H 4 O 2 isomers are not detected, and the derived upper limit for the column density is ≤3 × 10 14 cm −2 for glycolaldehyde and ≤2 × 10 15 cm −2 for acetic acid. From the 223 GHz continuum map, we identify several dust clumps with associated gas masses in the range 0.8 to 5.8 M . Assuming that the methyl formate is spatially distributed as the dust is, we find relative abundances of methyl formate in the range ≤0.1 × 10 −8 to 5.2 × 10 −8 . We suggest a relation between the methyl formate distribution and shocks as traced by 2.12 μm H 2 emission.

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Section: Interest Of Methyl Formate Observationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

HCOOCH₃as a probe of temperature and structure in Orion-KL

Favre

Despois

Brouillet

et al. 2011

A&A

100

238

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“…Since this discovery, approximately 900 lines of the ground torsional state have been detected in different interstellar molecular clouds, Sgr B2, Orion KL, and W51 e1/e2 (Lovas 2004). Recently torsionally excited lines of methyl formate have also been observed in Orion KL by Kobayashi et al (2007) and in W51 e2 by Demyk et al (2008). It has to be emphasized that such a large number of transitions of methyl formate could only Article published by EDP Sciences be identified in the interstellar medium thanks to a huge effort in the laboratory.…”

Section: Introductionmentioning

confidence: 98%

Rotational spectrum of¹³C₂-methyl formate (HCOO¹³CH₃) and detection of the two¹³C-methyl formate in Orion

Carvajal¹,

Margulès

Tercero

et al. 2009

A&A

116

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Context. Laboratory measurements and analysis of the microwave and millimeter-wave spectra of potential interstellar molecules are a prerequisite for their subsequent identification by radioastronomical techniques. The spectral analysis provides spectroscopic parameters that are used in the assignment procedure of the laboratory spectra, and that also predict the frequencies of transitions not measured in the laboratory with a high degree of precision.Aims. An experimental laboratory study and its theoretical analysis is presented for 13 C 2 -methyl formate (HCOO 13 CH 3 ) allowing a search for this isotopologue in the Orion molecular cloud. The 13 C 1 -methyl formate (H 13 COOCH 3 ) molecule was also searched for in this interstellar cloud, using previously published spectroscopic data. Methods. The experimental spectra of 13 C 2 -methyl formate were recorded in the microwave and sub-mm energy ranges (4-20 GHz, 8-80 GHz, 150-700 GHz). The spectra were analyzed using the Rho-Axis Method (RAM), which takes the CH 3 internal rotation and the coupling between internal rotation and global rotation into account. Results. Twenty-seven spectroscopic constants of 13 C 2 -methyl formate have been obtained from a fit of 936 transitions of the ground torsional state with a standard (unitless) deviation of 1.08. A prediction of line positions and intensities is also produced. This prediction allowed us to identify 230 13 C 2 -methyl formate lines in the Orion interstellar molecular cloud. We refitted all previously published ground state transitions of the 13 C 1 -methyl formate molecule in order to provide a prediction of its ground state spectrum. 234 lines of 13 C 1 -methyl formate were detected in the Orion interstellar cloud using that prediction.

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“…2007) to 3.4 × 10 17 cm −2 in G19.61-0.23 (Remijan et al 2004). Because of this fairly high column density, some lines from the first torsional state were also detected in Orion KL (Kobayashi et al 2007) and in W51e2 (Demyk et al 2008). …”

Section: Introductionmentioning

confidence: 93%

Microwave and submillimeter spectroscopy and first ISM detection of¹⁸O-methyl formate

Tercero

Margulès

Carvajal

et al. 2012

A&A

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Context. Astronomical survey of interstellar molecular clouds needs a previous analysis of the spectra in the microwave and sub-mm energy range to be able to identify them. We obtained very accurate spectroscopic constants in a comprehensive laboratory analysis of rotational spectra. These constants can be used to predict transition frequencies that were not measured in the laboratory very precisely. Aims. We present an experimental study and a theoretical analysis of two 18 O-methyl formate isotopologues, which were subsequently detected for the first time in Orion KL. Methods. The experimental spectra of both methyl formate isotopologues recorded in the microwave and sub-mm range from 1 to 660 GHz. Both spectra were analysed by using the rho-axis method (RAM) which takes into account the CH 3 internal rotation. Results. We obtained spectroscopic constants of both 18 O-methyl formate with high accuracy. Thousands of transitions were assigned and others predicted, which allowed us to detect both species in the IRAM 30 m line survey of Orion KL.

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Torsionally Excited Methyl Formate in Orion KL

Cited by 46 publications

References 21 publications

HCOOCH₃as a probe of temperature and structure in Orion-KL

HCOOCH₃as a probe of temperature and structure in Orion-KL

Rotational spectrum of¹³C₂-methyl formate (HCOO¹³CH₃) and detection of the two¹³C-methyl formate in Orion

Microwave and submillimeter spectroscopy and first ISM detection of¹⁸O-methyl formate

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Torsionally Excited Methyl Formate in Orion KL

Cited by 46 publications

References 21 publications

HCOOCH3as a probe of temperature and structure in Orion-KL

HCOOCH3as a probe of temperature and structure in Orion-KL

Rotational spectrum of13C2-methyl formate (HCOO13CH3) and detection of the two13C-methyl formate in Orion

Microwave and submillimeter spectroscopy and first ISM detection of18O-methyl formate

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HCOOCH₃as a probe of temperature and structure in Orion-KL

HCOOCH₃as a probe of temperature and structure in Orion-KL

Rotational spectrum of¹³C₂-methyl formate (HCOO¹³CH₃) and detection of the two¹³C-methyl formate in Orion

Microwave and submillimeter spectroscopy and first ISM detection of¹⁸O-methyl formate