2008ApJ...680..428G

We report the results of a 100 deg² survey of the Taurus molecular cloud region in ¹²CO and ¹³CO J=1⟶0. The image of the cloud in each velocity channel includes ≃3x10⁶ Nyquist-sampled pixels on a 20" grid. The high sensitivity and large spatial dynamic range of the maps reveal a very complex, highly structured cloud morphology, including filaments, cavities, and rings. The axes of the striations seen in the ¹²CO emission from relatively diffuse gas are aligned with the direction of the magnetic field. We have developed a statistical method for analyzing the pixels in which ¹²CO but not ¹³CO is detected, which allows us to determine the CO column in the diffuse portion of the cloud, as well as in the denser regions in which we detect both isotopologues. Using a column-density-dependent model for the CO fractional abundance, we derive the mass of the region mapped to be 2.4x10⁴ M_☉, more than twice as large as would be obtained using a canonical fixed fractional abundance of ¹³CO, and a factor of 3 greater than would be obtained considering only the high column density regions. We determine that half the mass of the cloud is in regions having column density below 2.1x10²¹/cm2. The distribution of young stars in the region covered is highly nonuniform, with the probability of finding a star in a pixel with a specified column density rising sharply for N(H₂)=6x10²¹/cm2. We determine a relatively low star formation efficiency (mass of young stars/mass of molecular gas), between 0.3% and 1.2%, and an average star formation rate during the past 3 Myr of 8x10^–5 stars/yr.