Carbon Chain Molecules Toward Embedded Low-Mass Protostars

Abstract

Carbon chain molecules may be an important reservoir of reactive organics during star and planet formation. Carbon chains have been observed toward several low-mass young stellar objects (YSOs), but their typical abundances and chemical relationships in such sources are largely unconstrained. We present a carbon chain survey toward 16 deeply embedded (Class 0/I) low-mass protostars made with the IRAM 30 m telescope. Carbon chains are found to be common at this stage of protostellar evolution. We detect CCS, CCCS, HC${}_3$N, HC${}_5$N, l-C${}_3$H, and C${}_4$H toward 88%, 38%, 75%, 31%, 81%, and 88% of sources, respectively. Derived column densities for each molecule vary by one to two orders of magnitude across the sample. As derived from survival analysis, median column densities range between 1.2$\times 10^{11}$ cm${}^{-2}$ (CCCS) and 1.5$\times 10^{13}$ cm${}^{-2}$ (C${}_4$H) and estimated fractional abundances with respect to hydrogen range between 2$\times 10^{-13}$ (CCCS) and 5$\times 10^{-11}$ (C${}_4$H), which are low compared to cold cloud cores, warm carbon chain chemistry (WCCC) sources, and protostellar model predictions. We find significant correlations between molecules of the same carbon chain families, as well as between the cyanpolyynes (HC${}_{\mathrm{n}}$N) and the pure hydrocarbon chains (C${}_{\mathrm{n}}$H). This latter correlation is explained by a closely-related production chemistry of C${}_{\mathrm{n}}$H and cyanpolyynes during low-mass star formation.

31 pages, 14 figures, accepted for publication in ApJ

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• Carbon-Chain Chemistry in the Interstellar Medium
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• Chemical survey of Class I protostars with the IRAM-30m
• Survey Observations to Study Chemical Evolution from High-Mass Starless Cores to High-Mass Protostellar Objects II. HC${}_3$N and N${}_2$H${}^{+}$
• A sensitive 3 mm line survey of L483: a broad view of the chemical composition of a core around a Class 0 object
• Hunting for hot corinos and WCCC sources in the OMC-2/3 filament
• The connection between warm carbon chain chemistry and interstellar irradiation of star-forming cores
• A 3mm chemical exploration of small organics in Class I YSOs
• Carbon-Chain Molecules in Molecular Outflows and Lupus I Region--New Producing Region and New Forming Mechanism
• Anatomy of the Class I protostar L1489 IRS with NOEMA -- I. Disk, streamers, outflow(s) and bubbles at 3mm
• A search for cloud cores affected by shocked carbon chain chemistry in L1251
• Carbon-chain molecule survey toward four low-mass molecular outflow sources
• Velocity-Coherent Substructure in TMC-1: Inflow and Fragmentation
• Carbon-Chain Chemistry vs. Complex-Organic-Molecule Chemistry in Envelopes around Three Low-Mass Young Stellar Objects in the Perseus Region
• Cyanopolyyne line survey towards high-mass star-forming regions with TMRT
• Anatomy of the Class I protostar L1489 IRS with NOEMA - II. A disk replenished by a massive streamer
• An 18-25 GHz spectroscopic survey of dense cores in the Chamaeleon I molecular cloud
• Clump-scale chemistry in the NGC2264-D cluster-forming region