Chemical survey toward young stellar objects in the Perseus molecular cloud complex

TL;DR

This study surveys the chemical composition of 36 protostars in the Perseus cloud, revealing significant diversity and environmental influences on molecular abundances, especially between hot corino and WCCC types.

Contribution

It provides an unbiased, large-scale chemical survey of low-mass protostars, highlighting environmental effects on chemical diversity and bridging hot corino and WCCC chemistries.

Findings

Significant chemical diversity among protostars with C2H/CH3OH ratios spanning 2 orders of magnitude.

Hot corino sources are rich in CH3OH but poor in C2H, with low C2H/CH3OH ratios.

Sources near cloud edges tend to have higher C2H/CH3OH ratios, indicating environmental impact.

Abstract

Chemical diversity of the gas in low-mass protostellar cores is widely recognized. In order to explore its origin, a survey of chemical composition toward 36 Class 0/I protostars in the Perseus molecular cloud complex, which are selected in an unbiased way under certain physical conditions, has been conducted with IRAM 30 m and NRO 45 m telescope. Multiple lines of C2H, c-C3H2 and CH3OH have been observed to characterize the chemical composition averaged over a 1000 au scale around the protostar. The derived beam-averaged column densities show significant chemical diversity among the sources, where the column density ratios of C2H/CH3OH are spread out by 2 orders of magnitude. From previous studies, the hot corino sources have abundant CH3OH but deficient C2H, their C2H/CH3OH column density ratios being relatively low. In contrast, the warm-carbon-chain chemistry (WCCC) sources are found to reveal the high C2H/CH3OH column density ratios. We find that the majority of the sources have intermediate characters between these two distinct chemistry types. A possible trend is seen between the C2H/CH3OH ratio and the distance of the source from the edge of a molecular cloud. The sources located near cloud edges or in isolated clouds tend to have a high C2H/CH3OH ratio. On the other hand, the sources having a low C2H/CH3OH ratio tend to be located in inner regions of the molecular cloud complex. This result gives an important clue to an understanding of the origin of the chemical diversity of protostellar cores in terms of environmental effects.