Dynamical timescale of precollapse evolution inferred from chemical
  distribution in the Taurus Molecular Cloud-1 (TMC-1) filament
  We present observations and analysis of the low-mass star-forming region,
Taurus Molecular Cloud-1 (TMC-1). CS ($J$=2-1)/N$_2$H$^+$ ($J$=1-0) and
C$^{17}$O ($J$=2-1)/C$^{18}$O ($J$=2-1) were observed with FCRAO (Five College
Radio Astronomy Observatory) and SRAO (Seoul Radio Astronomy Observatory),
respectively. In addition, Spitzer infrared data and 1.2 mm continuum data
observed with MAMBO (Max-Planck Millimetre Bolometer) are used. We also perform
chemical modeling to investigate the relative molecular distributions of the
TMC-1 filament. Based on Spitzer observations, there is no young stellar object
along the TMC-1 filament, while five Class II and one Class I young stellar
objects are identified outside the filament. The comparison between column
densities calculated from dust continuum and C$^{17}$O 2-1 line emission shows
that CO is depleted much more significantly in the ammonia peak than in the
cyanopolyyne peak, while the column densities calculated from the dust
continuum are similar at the two peaks. N$_2$H$^+$ is not depleted much in
either peak. According to our chemical calculation, the differential chemical
distribution in the two peaks can be explained by different timescales required
to reach the same density, i.e., by different dynamical processes.
