A Complete Search for Dense Cloud Cores in Taurus

We present the results of an H¹³CO⁺ J = 1-0 survey for dense molecular condensations in Taurus. The observations were carried out with the 45 m telescope at Nobeyama on the basis of an extensive C¹⁸O survey made with the 4 m telescope at Nagoya University. The present survey is based purely on molecular line observations and thus provides the most extensive and uniform sample of high-density condensations. We detected 55 H¹³CO⁺ condensations, of which 44 are starless. These starless condensations are compact (R ≲ 0.1 pc) and of high density (≳10⁵ cm^-3) and thus are highly probable candidates for protostellar condensations just before star formation. The striking feature of these starless compact condensations is the steep slope of the mass spectrum (dN/dM ~ M^-2.5 for 3.5 M_☉ < M < 20.1 M_☉). Under the assumption of uniform star formation efficiency, the spectrum resembles the stellar initial mass function (IMF) for a mass of ≲a few solar masses. This suggests that the stellar IMF is the result of the fragmentation process from relatively lower density cores. The statistical analysis of the starless condensations yields the lifetime of the condensations of ~4 × 10⁵ yr, which is several times longer than free-fall timescale. This short timescale compared with magnetic flux loss time may indicate that the timescale is determined by the dissipation timescale of turbulence.