Carbon-chain molecules in molecular outflows and Lupus I region – new producing region and new forming mechanism

Abstract

Using the new equipment of the Shanghai Tian Ma Radio Telescope, we have searched for carbon-chain molecules (CCMs) towards five outflow sources and six Lupus I starless dust cores, including one region known to be characterized by warm carbon-chain chemistry (WCCC), Lupus I-1 (IRAS 15398-3359), and one TMC-1 like cloud, Lupus I-6 (Lupus-1A). Lines of HC 3 N J = 2−1, HC 5 N J = 6−5, HC 7 N J = 14−13, 15−14, 16−15 and C 3 S J = 3−2 were detected in all the targets except in the outflow source L1660 and the starless dust core Lupus I-3/4. The column densities of nitrogen-bearing species range from 10 12 to 10 14 cm −2 and those of C 3 S are about 10 12 cm −2 . Two outflow sources, I20582+7724 and L1221, could be identified as new carbon-chain-producing regions. Four of the Lupus I dust cores are newly identified as early quiescent and dark carbon-chain-producing regions similar to Lup I-6, which together with the WCCC source, Lup I-1, indicate that carbon-chain-producing regions are popular in Lupus I which can be regard as a Taurus like molecular cloud complex in our Galaxy. The column densities of C 3 S are larger than those of HC 7 N in the three outflow sources I20582, L1221 and L1251A. Shocked carbon-chain chemistry (SCCC) is proposed to explain the abnormal high abundances of C 3 S compared with those of nitrogen-bearing CCMs. Gas-grain chemical models support the idea that shocks can fuel the environment of those sources with enough S + thus driving the generation of S-bearing CCMs.

A search for cloud cores affected by shocked carbon chain chemistry in L1251

“…The distance is adopted as 300 ± 30 pc derived from the 3-dimensional (3D) dust map based on Gaia (Green et al 2019). It is consistent with the values of 300±50 pc adopted by Kun & Prusti (1993) and 330±30 pc adopted by Balázs et al (2004) and Wu et al (2019a). Based on CO observations, the L1251 cloud was divided into five substructures by Sato et al (1994), and these substructures were designated by letters from A to E (see the top panel of Fig.…”

“…The main concept of SCCC is that the sulfur ions and atoms released from grain surfaces under the effect of shocks will mix with cold gas components and drive a new generation of carbon chain molecules, especially the sulfur-bearing ones such as C 3 S. The criteria of SCCC include relatively weak N-bearing CCM emissions in contrast to strong C 3 S emissions and signs of developed shock regions. Our model (Wu et al 2019a) forecasts that, in sources where the SCCC mechanism works most efficiently, the abundance of C 3 S (X(C 3 S)) will not only exceed that of HC 7 N (X(HC 7 N)), but also that of HC 5 N (X(HC 5 N)). The observations presented by Wu et al (2019a) show that so far known three SCCC sources (IRAS 20582+7724 (I20582), L1221 and L1251-IRS3) all have N(C 3 S)<N(HC 5 N), while L1251-IRS3 possesses a C 3 S column density closest to but still not exceeding that of HC 5 N.…”

“…Our model (Wu et al 2019a) forecasts that, in sources where the SCCC mechanism works most efficiently, the abundance of C 3 S (X(C 3 S)) will not only exceed that of HC 7 N (X(HC 7 N)), but also that of HC 5 N (X(HC 5 N)). The observations presented by Wu et al (2019a) show that so far known three SCCC sources (IRAS 20582+7724 (I20582), L1221 and L1251-IRS3) all have N(C 3 S)<N(HC 5 N), while L1251-IRS3 possesses a C 3 S column density closest to but still not exceeding that of HC 5 N.…”

“…1). The SCCC source denoted as L1251A (referred as L1251-IRS3 in this work) in Wu et al (2019a) contains IRS3. A well-collimated jet in north-south direction associated with IRS3 (see also Sect.…”

“…Recently we have observed six outflows and five starless Lupus cores using the Shanghai 65 m Tian Ma Radio Telescope (TMRT) to explore SCCC in L1251 3 the production region and excitation mechanism of CCMs (Wu et al 2019a). All the targets are located within 330 pc from the Earth.…”