Carbon-Chain Chemistry vs. Complex-Organic-Molecule Chemistry in Envelopes around Three Low-Mass Young Stellar Objects in the Perseus Region

Abstract

We have analyzed ALMA Cycle 5 data in Band 4 toward three low-mass young stellar objects (YSOs), IRAS 03235+3004 (hereafter IRAS 03235), IRAS 03245+3002 (IRAS 03245), and IRAS 03271+3013 (IRAS 03271), in the Perseus region. The HC${}_3$N ($J=16-15$; $E_{\mathrm{up}}/k=59.4$ K) line has been detected in all of the target sources, while four CH${}_3$OH lines ($E_{\mathrm{up}}/k=15.4-36.3$ K) have been detected only in IRAS 03245. Sizes of the HC${}_3$N distributions ($\sim 2930-3230$ au) in IRAS 03235 and IRAS 03245 are similar to those of the carbon-chain species in the warm carbon chain chemistry (WCCC) source L1527. The size of the CH${}_3$OH emission in IRAS 03245 is $\sim 1760$ au, which is slightly smaller than that of HC${}_3$N in this source. We compare the CH${}_3$OH/HC${}_3$N abundance ratios observed in these sources with predictions of chemical models. We confirm that the observed ratio in IRAS 03245 agrees with the modeled values at temperatures around 30--35 K, which supports the HC${}_3$N formation by the WCCC mechanism. In this temperature range, CH${}_3$OH does not thermally desorb from dust grains. Non-thermal desorption mechanisms or gas-phase formation of CH${}_3$OH seem to work efficiently around IRAS 03245. The fact that IRAS 03245 has the highest bolometric luminosity among the target sources seems to support these mechanisms, in particular the non-thermal desorption mechanisms.

Accepted by The Astrophysical Journal, 13 pages, 5 figures, 7 tables

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Cited by in corpus (3)

• Vibrationally-excited Lines of HC${}_3$N Associated with the Molecular Disk around the G24.78+0.08 A1 Hyper-compact H${}_{\mathrm{II}}$ Region
• Parsec scales of carbon chain and complex organic molecules in AFGL 2591 and IRAS 20126
• Clump-scale chemistry in the NGC2264-D cluster-forming region