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. This first release includes the data for four regions in the Gould Belt clouds: B18 in Taurus, NGC 1333 in Perseus, L1688 in Ophiuchus, and Orion A North in Orion. We compare the NH₃ emission to dust continuum emission from 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, {σ }_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 {σ }_v and T _K with increasing star formation activity. The data presented in this paper are publicly available (https://dataverse.harvard.edu/dataverse/GAS_DR1).