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