Nobeyama molecular line survey of SCUBA-2 cores

We present the results of a single-pointing survey of 207 dense cores embedded in Planck Galactic Cold Clumps distributed in five different environments ({lambda} Orionis, Orion A, Orion B, the Galactic plane, and high latitudes) to identify dense cores on the verge of star formation for the study of the initial conditions of star formation. We observed these cores in eight molecular lines at 76-94GHz using the Nobeyama 45m telescope.

We find that early-type molecules (e.g., CCS) have low detection rates and that late-type molecules (e.g., N_2_H^+^ and c-C_3_H_2_) and deuterated molecules (e.g., N_2_D^+^ and DNC) have high detection rates, suggesting that most of the cores are chemically evolved. The deuterium fraction (D/H) is found to decrease with increasing distance, indicating that it suffers from differential beam dilution between the D/H pair of lines for distant cores (>1kpc).