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Green Bank Ammonia Survey (GAS)

Orion composite view
A ribbon of ammonia — a tracer of star-forming gas — in the Orion Nebula as seen with the GBT (orange). Background in blue is a WISE telescope infrared image showing the dust in the region. GBO/AUI/NSF

The Green Bank Ammonia Survey (GAS) is an ambitious legacy survey to map emission from the 23 GHz NH3 inversion transitions toward all the northern Gould Belt star forming regions with Av > 7.

The Gould Belt is a ring of young stars and star-forming regions that contains nearly all the ongoing, predominantly low-mass star formation wihtin 500 pc of the Sun. These nearby star-forming clouds range in size and activity, from the nearly inactive Pipe Nebula, through the star-forming but largely quiescent Taurus molecular cloud, to stellar group- and cluster-forming clouds like Perseus and Ophiuchus. The Orion molecular cloud is our nearest example of a high mass star forming region. This variation in star formation activity, coupled with their nearby distances, make the Gould Belt clouds an excellent survey target to understand how star formation proceeds in different environments, and to test and constrain star formation theories and simulations through detailed observations.

Within this distance range, the GBT beam at 23 GHz subtends 0.02 pc – 0.08 pc, able to resolve both the Jeans length and the ~ 0.1 pc typical filament width suggested by Herschel data, and will provide the kinematic counterpoint to Herschel and JCMT Gould Belt continuum surveys. With these data we will 1) evaluate the stability of dense gas structures as a function of scale, 2) track the dissipation of turbulence and evolution of angular momentum in filaments and cores, and 3) quantitatively test predictions of models of core and filament formation via mass flows and accretion.

A ribbon of ammonia — a tracer of star-forming gas — in the Orion Nebula as seen with the GBT GBO/AUI/NSF

GAS will produce a Legacy dataset for the GBT, NRAO, and the star formation community. We will release fully-reduced data cubes for all observed regions in parallel with acceptance of their companion papers. Links to GAS papers and datasets are given below.

Software

The software used to calibrate, grid, and analyse the GAS data are available on github:

https://github.com/GBTAmmoniaSurvey

GAS Papers

Friesen, Pineda et al. 2017, ApJ, 843, 63
Kirk et al. 2017, ApJ, 846, 144
Keown et al. 2017, ApJ, 850, 3
Redaelli et al. 2017, ApJ, 850, 202

Publicly released datasets, including cubes and property maps

https://dataverse.harvard.edu/dataverse/GAS_Project

Team members

Rachel Friesen (NRAO), Jaime Pineda (MPE) (co-PIs)

F. Alves, H. Arce, P. Caselli, A. Chacon, H. Chen, M. Chen, J. Di
Francesco, A. Ginsberg, A. Goodman, F. Heitsch, J. Keown, H. Kirk,
P. Martin, C. Matzner, P. Myers, S. Offner, A. Punanova, E. Redaelli,
E. Rosolowsky, Y. Seo, Y. Shirley, A. Singh


Outside press

http://www.syfy.com/syfywire/a-500-trillion-km-long-streamer-of-ammonia-in-orion