RT Journal Article
T1 Impact of nonconvergence and various approximations of the partition function on the molecular column densities in the interstellar medium
A1 Carvajal Zaera, Miguel
A1 Favre, Cecile
A1 Kleiner, Isabelle
A1 Ceccarelli, Cecilia
A1 Bergin, E. A.
A1 Fedele, Maddalena
AB We emphasize that the completeness of the partition function, that is, the use of a converged partition function at the typical temperaturerange of the survey, is very important to decrease the uncertainty on this quantity and thus to derive reliable interstellar moleculardensities. In that context, we show how the use of different approximations for the rovibrational partition function together withsome interpolation and/or extrapolation procedures may affect the estimate of the interstellar molecular column density. For thatpurpose, we apply the partition function calculations to astronomical observations performed with the IRAM-30m telescope towardsthe NGC 7538–IRS1 source of two N-bearing molecules: isocyanic acid (HNCO, a quasilinear molecule) and methyl cyanide (CH3CN,a symmetric top molecule). The case of methyl formate (HCOOCH3), which is an asymmetric top O-bearing molecule containingan internal rotor is also discussed. Our analysis shows that the use of different partition function approximations leads to relativedifferences in the resulting column densities in the range 9–43%. Thus, we expect this work to be relevant for surveys of sources withtemperatures higher than 300K and to observations in the infrared.
PB Springer Verlag
SN 1432-0746
YR 2019
FD 2019-07
LK http://hdl.handle.net/10272/16683
UL http://hdl.handle.net/10272/16683
LA eng
NO Carvajal Zaera, M., Favre, C., Kleiner, I., Ceccarelli, C., Bergin, E. A., & Fedele, D. (2019). Impact of nonconvergence and various approximations of the partition function on the molecular column densities in the interstellar medium. Astronomy & Astrophysics, 627, A65. DOI: https://doi.org/10.1051/0004-6361/201935469
NO This work is partly supported by CMST COST Action CM1401 Our Astro-Chemical History and CMST COST Action CM1405 MOLIM. The work of C.F. is supported by the French National Research Agency in the framework of the Investissements d'Avenir program (ANR-15-IDEX-02), through the funding of the "Origin of Life" project of the Universite Grenoble-Alpes. C.C. and C.F. acknowledge funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme, for the Project "The Dawn of Organic Chemistry" (DOC), grant agreement No 741002. I.K. would like to thank the French programme of Chimie Interstellaire PCMI. C.F. and D.F. acknowledge support from the Italian Ministry of Education, Universities and Research, project SIR (RBSI14ZRHR). E.A.B. acknowledges support from NSF (AST-1514670) and NASA (NNX16AB48G). M.C. acknowledges the financial support from FIS2014-53448-C2-2-P (MINECO, Spain), from the Centro de Estudios Avanzados de Fisica, Matematicas y Computacion (CEAFMC) of the University of Huelva and from the Consejeria de Conocimiento, Investigacion y Universidad, Junta de Andalucia and European Regional Development Fund (ERDF), ref. SOMM17/6105/UGR. The authors acknowledge the referee for his/her valuable comments.
DS Repositorio Institucional de la Universidad de Huelva
RD 31 may 2026