A particular carbon-chain-producing region: L1489 starless core
  We detected carbon-chain molecules (CCMs) HC2n+1N (n=1-3) and C3S in Ku band
as well as {high-energy excitation lines including C4H N=9-8, J=17/2-15/2,
19/2-17/2, and CH3CCH J=5-4, K=2 in the 3 mm band toward a starless core called
the eastern molecular core (EMC) of L1489 IRS. Maps of all the observed lines
were also obtained. Comparisons with a number of early starless cores and WCCC
source L1527 show that the column densities of C4H and CH3CCH are close to
those of L1527, and the CH3CCH column densities of the EMC and L1527 are
slightly higher than those of TMC-1. The EMC and L1527 have similar C3S column
densities, but they are much lower than those of all the starless cores, with
only 6.5% and 10% of the TMC-1 value, respectively. The emissions of the
N-bearing species of the EMC and L1527 are at the medium level of the starless
cores. These comparisons show that the CCM emissions in the EMC are similar to
those of L1527, though L1527 contains a protostar. Although dark and quiescent,
the EMC is warmer and at a later evolutionary stage than classical
carbon-chain--producing regions in the cold, dark, quiescent early phase. The
PACS, SPIRE, and SCUBA maps evidently show that the L1489 IRS seems to be the
heating source of the EMC. Although it is located at the margins of the EMC,
its bolometric luminosity and bolometric temperature are relatively high. Above
all, the EMC is a rather particular carbon-chain-producing region and is quite
significant for CCM science.
