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Title: METHANOL IN THE STARLESS CORE, TAURUS MOLECULAR CLOUD-1

Abstract

To explore the formation mechanisms of gas phase CH{sub 3}OH in cold starless cores, we have conducted high spectral resolution observations toward the cyanopolyyne peak of Taurus Molecular Cloud-1 (TMC-1 CP) with the IRAM 30 m telescope, the Green Bank Telescope, and the Nobeyama 45 m telescope. The spectral lines of CH{sub 3}OH toward TMC-1 CP are found to have a double-peaked profile separated by 0.5 km s{sup −1}. Since the double-peaked profile is observed for {sup 13}CH{sub 3}OH, it is not due to optical depth and/or self-absorption effects. The spectral line profile of CH{sub 3}OH is much different from those of C{sup 34}S, C{sub 3}S, and HC{sub 7}N observed toward this source. The H{sub 2} densities of the emitting region of CH{sub 3}OH for the blueshifted and redshifted components are derived to be (1.7 ± 0.5) × 10{sup 4} cm{sup −3} and (4.3 ± 1.2) × 10{sup 4} cm{sup −3}, respectively. These densities are similar to or slightly lower than those found for the other molecules. These results suggest a chemical differentiation between CH{sub 3}OH and the other molecules, which has indeed been confirmed by mapping observations of the CH{sub 3}OH and C{sup 34}S lines. These results are consistentmore » with the general idea that CH{sub 3}OH is formed on dust grains and is liberated into the gas phase by non-thermal desorption. The grain-surface origin of CH{sub 3}OH is further confirmed by the CH{sub 3}OH/{sup 13}CH{sub 3}OH ratio. Weak shocks caused by accreting diffuse gas to the TMC-1 filament, photoevaporation caused by cosmic-ray induced UV radiation, and the desorption of excess reaction energy in the formation of CH{sub 3}OH on dust grains are discussed for the desorption mechanisms.« less

Authors:
; ; ;  [1]
  1. Department of Physics, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033 (Japan)
Publication Date:
OSTI Identifier:
22522005
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 802; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CLOUDS; COSMIC DUST; COSMIC RADIATION; DENSITY; DESORPTION; FILAMENTS; HYDROGEN; METHANOL; MOLECULES; RED SHIFT; SELF-ABSORPTION; TELESCOPES; ULTRAVIOLET RADIATION

Citation Formats

Soma, Tatsuya, Sakai, Nami, Watanabe, Yoshimasa, and Yamamoto, Satoshi, E-mail: soma@taurus.phys.s.u-tokyo.ac.jp. METHANOL IN THE STARLESS CORE, TAURUS MOLECULAR CLOUD-1. United States: N. p., 2015. Web. doi:10.1088/0004-637X/802/2/74.
Soma, Tatsuya, Sakai, Nami, Watanabe, Yoshimasa, & Yamamoto, Satoshi, E-mail: soma@taurus.phys.s.u-tokyo.ac.jp. METHANOL IN THE STARLESS CORE, TAURUS MOLECULAR CLOUD-1. United States. doi:10.1088/0004-637X/802/2/74.
Soma, Tatsuya, Sakai, Nami, Watanabe, Yoshimasa, and Yamamoto, Satoshi, E-mail: soma@taurus.phys.s.u-tokyo.ac.jp. Wed . "METHANOL IN THE STARLESS CORE, TAURUS MOLECULAR CLOUD-1". United States. doi:10.1088/0004-637X/802/2/74.
@article{osti_22522005,
title = {METHANOL IN THE STARLESS CORE, TAURUS MOLECULAR CLOUD-1},
author = {Soma, Tatsuya and Sakai, Nami and Watanabe, Yoshimasa and Yamamoto, Satoshi, E-mail: soma@taurus.phys.s.u-tokyo.ac.jp},
abstractNote = {To explore the formation mechanisms of gas phase CH{sub 3}OH in cold starless cores, we have conducted high spectral resolution observations toward the cyanopolyyne peak of Taurus Molecular Cloud-1 (TMC-1 CP) with the IRAM 30 m telescope, the Green Bank Telescope, and the Nobeyama 45 m telescope. The spectral lines of CH{sub 3}OH toward TMC-1 CP are found to have a double-peaked profile separated by 0.5 km s{sup −1}. Since the double-peaked profile is observed for {sup 13}CH{sub 3}OH, it is not due to optical depth and/or self-absorption effects. The spectral line profile of CH{sub 3}OH is much different from those of C{sup 34}S, C{sub 3}S, and HC{sub 7}N observed toward this source. The H{sub 2} densities of the emitting region of CH{sub 3}OH for the blueshifted and redshifted components are derived to be (1.7 ± 0.5) × 10{sup 4} cm{sup −3} and (4.3 ± 1.2) × 10{sup 4} cm{sup −3}, respectively. These densities are similar to or slightly lower than those found for the other molecules. These results suggest a chemical differentiation between CH{sub 3}OH and the other molecules, which has indeed been confirmed by mapping observations of the CH{sub 3}OH and C{sup 34}S lines. These results are consistent with the general idea that CH{sub 3}OH is formed on dust grains and is liberated into the gas phase by non-thermal desorption. The grain-surface origin of CH{sub 3}OH is further confirmed by the CH{sub 3}OH/{sup 13}CH{sub 3}OH ratio. Weak shocks caused by accreting diffuse gas to the TMC-1 filament, photoevaporation caused by cosmic-ray induced UV radiation, and the desorption of excess reaction energy in the formation of CH{sub 3}OH on dust grains are discussed for the desorption mechanisms.},
doi = {10.1088/0004-637X/802/2/74},
journal = {Astrophysical Journal},
number = 2,
volume = 802,
place = {United States},
year = {Wed Apr 01 00:00:00 EDT 2015},
month = {Wed Apr 01 00:00:00 EDT 2015}
}