Possible gas-phase syntheses for seven neutral molecules studied recently with the Green Bank Telescope

Free access article

Issue		A&A Volume 474, Number 2, November I 2007


Page(s)		521 - 527
Section		Interstellar and circumstellar matter
DOI		http://dx.doi.org/10.1051/0004-6361:20078246

A&A 474, 521-527 (2007)
DOI: 10.1051/0004-6361:20078246

Possible gas-phase syntheses for seven neutral molecules studied recently with the Green Bank Telescope

D. Quan¹ and E. Herbst²

¹ Chemical Physics Program, The Ohio State University, Columbus, Ohio 43210, USA
e-mail: herbst@mps.ohio-state.edu
² Departments of Physics, Chemistry and Astronomy, The Ohio State University, Columbus, OH 43210, USA

(Received 9 July 2007 / Accepted 17 August 2007)

Abstract
Aims.With the Green Bank telescope (GBT), seven neutral molecules have been newly detected or confirmed towards either the cold interstellar core TMC-1 or the hot core source Sgr B2(N) within the last 1-2 years. Towards TMC-1, the new molecules seen are cyanoallene (CH₂CCHCN) and methyl triacetylene (CH₃C₆H) while methyl cyanoacetylene (CH₃CCCN) and methyl cyanodiacetylene (CH₃C₅N) were confirmed. Towards Sgr B2(N), the three newly detected molecules are cyclopropenone (c-C₃H₂O), ketenimine (CH₂CNH), and acetamide (CH₃CONH₂); these are mainly seen in absorption and are primarily located in an envelope around the hot core. In this work, we report a detailed study of the gas-phase chemistry of all seven molecules.
Methods.Starting with our updated gas-phase chemical reaction network osu.01.2007, we added formation and depletion reactions to treat the chemistry of each of the seven molecules. Some of these were already in our network but with incomplete chemistry, while most were not in the network at all prior to this work. We assumed the standard physical conditions for TMC-1 and assumed that these also hold for the envelope around Sgr B2(N). Standard pseudo-time-dependent calculations were run for each source.
Results.For TMC-1, we reproduced the observed fractional abundances of three detected molecules at early times of 10^5-6 yr and came close to reproducing a fourth. For the halo surrounding Sgr B2(N), our results are more ambiguous: only for ketenimine were we able to match the observed abundance very well.

Key words: ISM: abundances -- ISM: molecules -- molecular processes

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.

If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.