Ammonia Fitting of Multiple Velocity Components in High-Mass Star-Forming Regions

Abstract

We perform a multiple velocity component analysis of ammonia (NH₃) gas from KEYSTONE, a Green Bank Telescope survey covering 11 giant molecular clouds (GMCs) at distances from 0.7 to 2.7 kpc. We extend existing codes to enable simultaneous fitting of up to three velocity components in NH₃ (1,1) with radiative transfer. Using our multiple component fitting technique, we produce the best maps of the centroid velocity and velocity dispersion in these clouds to date. Over the entire survey, multiple velocity components were seen in 13% of pixels where we detect and fit NH₃ emission, primarily in clusters at the heart of the GMCs. In these multiple component pixels, the median measured NH₃ linewidth decreased by a factor of 1.4 compared to equivalent single-component measurements, but there are also significant cloud-to-cloud variations. Regions with multiple velocity components tend to be found in the densest zones of the GMCs and at the sites of high-mass star formation, indicative of multiple filaments, cores, or complex velocities associated with the formation of massive stars. Disentangling these velocity features will allow future quantitative analysis of coherent motions, such as infall and outflow, in these complex environments. The multi-component data products are available on the CADC.

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BibTeX RIS

BibTeX

@misc{withers2026ammonia,
  title = {{Ammonia Fitting of Multiple Velocity Components in High-Mass Star-Forming Regions}},
  author = {T. Withers and S. Sadavoy and M. Chen and J. Di Francesco and R. Friesen and J. Keown and E. Rosolowsky and H. Kirk and A. Ginsburg and L. D. Anderson and P. Caselli and D. Elia and E. Figura and H. -L. Liu and A. P. Marston and F. Motte and S. Offner and S. Pezzuto and P. Sanhueza and E. Schisano and N. Schneider and I. W. Stephens},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2610.28746},
  eprint = {2610.28746},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2610.28746},
  note = {CC BY-SA 4.0},
}

RIS

TY  - UNPB
TI  - Ammonia Fitting of Multiple Velocity Components in High-Mass Star-Forming Regions
AU  - T. Withers
AU  - S. Sadavoy
AU  - M. Chen
AU  - J. Di Francesco
AU  - R. Friesen
AU  - J. Keown
AU  - E. Rosolowsky
AU  - H. Kirk
AU  - A. Ginsburg
AU  - L. D. Anderson
AU  - P. Caselli
AU  - D. Elia
AU  - E. Figura
AU  - H. -L. Liu
AU  - A. P. Marston
AU  - F. Motte
AU  - S. Offner
AU  - S. Pezzuto
AU  - P. Sanhueza
AU  - E. Schisano
AU  - N. Schneider
AU  - I. W. Stephens
PY  - 2026
DA  - 2026/10/20
PB  - arXiv
DO  - 10.48550/arxiv.2610.28746
UR  - https://arxiv.org/abs/2610.28746
AB  - We perform a multiple velocity component analysis of ammonia (NH_3) gas from KEYSTONE, a Green Bank Telescope survey covering 11 giant molecular clouds (GMCs) at distances from 0.7 to 2.7 kpc. We extend existing codes to enable simultaneous fitting of up to three velocity components in NH_3 (1,1) with radiative transfer. Using our multiple component fitting technique, we produce the best maps of the centroid velocity and velocity dispersion in these clouds to date. Over the entire survey, multiple velocity components were seen in 13% of pixels where we detect and fit NH_3 emission, primarily in clusters at the heart of the GMCs. In these multiple component pixels, the median measured NH_3 linewidth decreased by a factor of 1.4 compared to equivalent single-component measurements, but there are also significant cloud-to-cloud variations. Regions with multiple velocity components tend to be found in the densest zones of the GMCs and at the sites of high-mass star formation, indicative of multiple filaments, cores, or complex velocities associated with the formation of massive stars. Disentangling these velocity features will allow future quantitative analysis of coherent motions, such as infall and outflow, in these complex environments. The multi-component data products are available on the CADC.
ER  -

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