Year: 2024
Type: article
Abstract: Context. Evidence that the chemical characteristics around low- and high-mass protostars are similar has been found: notably, a variety of carbon-chain species and complex organic molecules (COMs) form around both types. On the other hand, the chemical compositions around intermediate-mass (IM) protostars (2 M⊙ < m* < 8 M⊙) have not been studied with large samples. In particular, it is unclear the extent to which carbon-chain species form around them. Aims. We aim to obtain the chemical compositions of a sample of IM protostars, focusing particularly on carbon-chain species. We also aim to derive the rotational temperatures of HC5N to confirm whether carbon-chain species are formed in the warm gas around these stars. Methods. We conducted Q-band (31.5–50 GHz) line survey observations toward 11 mainly IM protostars with the Yebes 40 m radio telescope. The target protostars were selected from a subsample of the source list of the SOFIA Massive Star Formation project. Assuming local thermodynamic equilibrium, we derived the column densities of the detected molecules and the rotational temperatures of HC5N and CH3 OH. Results. Nine carbon-chain species (HC3N, HC5N, C3H, C4H linear-H2CCC, cyclic-C3H2, CCS, C3S, and CH3CCH), three COMs (CH3OH, CH3CHO, and CH3CN), H2CCO, HNCO, and four simple sulfur-bearing species (13CS, C34S, HCS+, and H2CS) are detected. The rotational temperatures of HC5N are derived to be ~20–30 K in three IM protostars (Cepheus E, HH288, and IRAS 20293+3952). The rotational temperatures of CH3OH are derived in five IM sources and found to be similar to those of HC5N. Conclusions. The rotational temperatures of HC5N around the three IM protostars are very similar to those around low- and high-mass protostars. These results indicate that carbon-chain molecules are formed in lukewarm gas (~20–30 K) around IM protostars via the warm carbon-chain chemistry process. Thus, carbon-chain formation occurs ubiquitously in the warm gas around protostars across a wide range of stellar masses. Carbon-chain molecules and COMs coexist around most of the target IM protostars, which is similar to the situation for low- and high-mass protostars. In summary, the chemical characteristics around protostars are the same in the low-, intermediate- and high-mass regimes.
Authors: Kotomi Taniguchi, Prasanta Gorai, Jonathan C. Tan, Miguel Gómez-Garrido, Rubén Fedriani, Yao-Lun Yang, Sridharan Tirupati Kumara, Kei E. I. Tanaka, Masao Saito, Yichen Zhang, Lawrence Morgan, Giuliana Cosentino, Chi-Yan Law
Institutions: National Institutes of Natural Sciences, National Astronomical Observatory of Japan, University of Oslo, University of Virginia, Chalmers University of Technology, Instituto de Astrofísica de Andalucía, RIKEN, National Radio Astronomy Observatory, Institute of Science Tokyo, The Graduate University for Advanced Studies, SOKENDAI, Shanghai Jiao Tong University, European Southern Observatory, Arcetri Astrophysical Observatory
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Awards: Revealing chemical reactions in high-mass star-forming regions with observations, laboratory experiments, and chemical network simulations, G1980387430, G2262748287, G3092233876, G3480869486, G3681454997, G4042783231, G425668148, G463062595, Icy Origins of Organic Molecules Unveiled by JWST, G5894067328, レーザー誘起再帰蛍光法による未同定星間分子吸収線の起源分子探索, 古代説話における諸寺縁起の研究, 原始星周囲の化学的多様性と星形成過程・物理環境との関係の解明, G8616911079, G8684520763, Massive Star Formation through the Universe, G980572351
OpenAlex ID: W6921735463
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