Distribution of CCS and HC3N in L1147, an Early Phase Dark Cloud

TL;DR

This study maps CCS and HC3N molecules in the early-stage dark cloud L1147, revealing spatial distributions, chemical variations, and confirming its status as a carbon-chain producing region, using radio telescope observations and chemical modeling.

Contribution

First detailed spatial mapping of CCS and HC3N in L1147, demonstrating chemical variation effects and confirming its classification as a CCPR.

Findings

Three cores identified along the filament with distinct CCS and HC3N distributions.

Column densities are lower than in other CCPRs, indicating early evolutionary stage.

Chemical models suggest density variations cause significant changes in molecular ratios.

Abstract

We used the Nobeyama 45 m radio telescope to reveal spatial distributions of CCS and HC$_3$N in L1147, one of carbon-chain producing regions (CCPRs) candidates, where carbon-chain molecules are dominant rather than NH$_3$. We found that three cores (two CCS cores and one HC$_3$N core) exist along the NE-SW filament traced by the 850 micron dust continuum, which are away from a Very Low Luminosity Object (VeLLO - a source that may turn into sub-stellar mass brown dwarf). The column densities of CCS are 3-7x10$^{12}$ cm$^{-2}$ and those of HC$_3$N are 2-6x10$^{12}$ cm$^{-2}$, respectively, much lower than those previously reported towards other CCPRs. We also found that two CCS peaks are displaced from that of HC$_3$N. In order to interpret such interleaved distributions, we conducted chemical reaction network simulations, and found that slightly different gas densities could lead to large variation of CCS-to-HC$_3$N ratio in the early phase of dark cloud evolution. Such a chemical "variation" may be seen in other CCPRs. Finally we were able to confirm that the L1147 filament can be regarded as a CCPR.