ATLASGAL - Ammonia observations towards the southern Galactic Plane
M. Wienen, F.Wyrowski, K. M. Menten, J. S. Urquhart, C. M. Walmsley,, T. Csengeri, B. S. Koribalski, F. Schuller

TL;DR
This study uses ammonia observations to analyze the physical conditions of high-mass star-forming regions in the Galactic plane, revealing temperature, turbulence, and hyperfine anomalies in molecular clumps.
Contribution
It provides detailed ammonia-based measurements of 354 star-forming clumps, highlighting new insights into their temperature, dynamics, and hyperfine structure anomalies, advancing understanding of early high-mass star formation.
Findings
Median NH3(1,1) line width ~2 km/s
Rotational temperatures from 12 to 28 K
Hyperfine anomalies observed in 49% of sources
Abstract
The initial conditions of molecular clumps in which high-mass stars form are poorly understood. In particular, a more detailed study of the earliest evolutionary phases is needed. The APEX Telescope Large Area Survey of the whole inner Galactic disk at 870 micron, ATLASGAL, has been conducted to discover high-mass star-forming regions at different evolutionary phases. Using the Parkes telescope, we observed the NH3 (1,1) to (3,3) inversion transitions towards 354 ATLASGAL clumps in the fourth quadrant. For a subsample of 289 sources, the N2H+ (1-0) line was measured with the Mopra telescope. We measured a median NH3(1,1) line width of about 2 km/s and rotational temperatures from 12 to 28 K with a mean of 18 K. For a subsample with detected NH3 (2,2) hyperfine components, we found that the commonly used method to compute the (2,2) optical depth from the (1,1) optical depth and the (2,2)…
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