Abundance anomaly of the 13C species of CCH
Department of Physics and Research Center for the Early Universe, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan e-mail: [nami;osamu]@taurus.phys.s.u-tokyo.ac.jp; email@example.com
2 Institute of Astronomy, The University of Tokyo, Osawa, Mitaka, Tokyo, 181-8588, Japan e-mail: firstname.lastname@example.org
3 Nobeyama Radio Observatory and Graduate University for Advanced Studies, Minamimaki, Minamisaku, Nagano 384-1305, Japan e-mail: email@example.com
Accepted: 15 December 2009
Aims. We have observed the N = 1-0 lines of CCH and its 13C isotopic species toward a cold dark cloud, TMC-1 and a star-forming region, L1527, to investigate the 13C abundances and formation pathways of CCH.
Methods. The observations have been carried out with the IRAM 30 m telescope.
Results. We have successfully detected the lines of 13CCH and C13CH toward the both sources and found a significant intensity difference between the two 13C isotopic species. The [C13CH] /[13CCH] abundance ratios are 1.6 ± 0.4 (3σ) and 1.6 ± 0.1 (3σ) for TMC-1 and L1527, respectively. The abundance difference between C13CH and 13CCH means that the two carbon atoms of CCH are not equivalent in the formation pathway. On the other hand, the [CCH]/[C13CH] and [CCH]/[13CCH] ratios are evaluated to be larger than 170 and 250 toward TMC-1, and to be larger than 80 and 135 toward L1527, respectively. Therefore, both of the 13C species are significantly diluted in comparison with the interstellar 12C/13C ratio of 60. The dilution is discussed in terms of a behavior of 13C in molecular clouds.
Key words: astrochemistry / ISM: molecules / ISM: abundances / ISM: individual objects: TMC-1 / ISM: individual objects: L1527
© ESO, 2010