The Green Bank Ammonia Survey: First Results of NH₃ Mapping of the Gould Belt

We present an overview of the first data release (DR1) and first-look science from the Green Bank Ammonia Survey (GAS). GAS is a Large Program at the Green Bank Telescope to map all Gould Belt star-forming regions with A_V ≳ 7 mag visible from the northern hemisphere in emission from NH₃ and other key molecular tracers. his first release includes the data for four regions in the ould Belt clouds: B18 in Taurus, NGC 1333 in Perseus, 1688 in Ophiuchus, and Orion A North in Orion. We compare the NH₃ emission to dust continuum emission rom Herschel and find that the two tracers correspond closely. We find that NH₃ is present in over 60% of the lines of sight with A_V ≳ 7 mag in three of the four DR1 regions, in agreement with expectations from previous observations. The sole exception is B18, where NH₃ is detected toward ∼40% of the lines of sight with A_V ≳ 7 mag. Moreover, we find that the NH₃ emission is generally extended beyond the typical 0.1 pc length scales of dense cores. We produce maps of the gas kinematics, temperature, and NH₃ column densities through forward modeling of the hyperfine structure of the NH₃ (1, 1) and (2, 2) lines. We show that the NH₃ velocity dispersion, s_v, and gas kinetic temperature, T_K, vary systematically between the regions included in this release, with an increase in both the mean value and the spread of sv and TK with increasing star formation activity. The data presented in this paper are publicly available (https://dataverse.harvard.edu/dataverse/GAS-DR1).