# The Green Bank Ammonia Survey (GAS): First Results of NH3 mapping the Gould Belt

## TL;DR

The Green Bank Ammonia Survey (GAS) provides detailed NH3 emission maps of Gould Belt star-forming regions, revealing correlations with dust, gas kinematics, and temperature variations linked to star formation activity.

## Contribution

This study presents the first data release of GAS, mapping NH3 in multiple Gould Belt regions and analyzing its relation to dust emission, gas dynamics, and temperature, offering new insights into star formation environments.

## Key findings

- NH3 emission closely matches dust emission in most regions.
- NH3 is detected in over 60% of dense lines-of-sight, except B18.
- Gas temperature and velocity dispersion increase with star formation activity.

## Abstract

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 $A_V \gtrsim 7$ mag visible from the northern hemisphere in emission from NH$_3$ and other key molecular tracers. This first release includes the data for four regions in Gould Belt clouds: B18 in Taurus, NGC 1333 in Perseus, L1688 in Ophiuchus, and Orion A North in Orion. We compare the NH$_3$ emission to dust continuum emission from Herschel, and find that the two tracers correspond closely. NH$_3$ is present in over 60\% of lines-of-sight with $A_V \gtrsim 7$ mag in three of the four DR1 regions, in agreement with expectations from previous observations. The sole exception is B18, where NH$_3$ is detected toward ~ 40\% of lines-of-sight with $A_V \gtrsim 7$ mag. Moreover, we find that the NH$_3$ emission is generally extended beyond the typical 0.1 pc length scales of dense cores. We produce maps of the gas kinematics, temperature, and NH$_3$ column densities through forward modeling of the hyperfine structure of the NH$_3$ (1,1) and (2,2) lines. We show that the NH$_3$ velocity dispersion, ${\sigma}_v$, and gas kinetic temperature, $T_K$, vary systematically between the regions included in this release, with an increase in both the mean value and spread of ${\sigma}_v$ and $T_K$ with increasing star formation activity. The data presented in this paper are publicly available.