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PreprintarXiv licencearXiv

A compact NH2D source without NH3 counterpart in the S187 high-mass star-forming region

  • E. A. Trofimova
  • I. I. Zinchenko
  • C. Henkel
  • A. G. Pazukhin
  • A. F. Punanova
  • P. M. Zemlyanukha
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Abstract

Our goal is to investigate a so far only tentatively detected compact NH2D source devoid of a notable NH3 counterpart, located rather close to the luminous IRAS 01202+6133 source (the projected distance is ≲0.3 pc) in the S187 high-mass star-forming region. A high ammonia deuteration in such an environment is unusual. We performed observations of this area with the 20-m OSO radio telescope in several frequency ranges from ∼72 to ∼112 GHz. The area was mapped at the lower frequencies while at the higher frequencies only the position of the NH2D emission peak was observed. The data were analyzed using non-LTE modeling. The data confirm a compact NH2D source with a size of ≲0.2 pc. In addition, emission from about 20 molecules was detected, but only the DCO+(1-0) peak coincides with the NH2D clump. The clump is not associated with any known astronomical source or an NH3 emission peak but the dust continuum map shows an enhancement at approximately the same position. The gas kinetic temperature derived from various indicators is ∼20-30 K, which possibly characterizes the surrounding material. The intrinsic NH2D line width (∼0.4 km/s) implies a clump with subsonic or transonic turbulence. The ortho/para NH2D line intensity ratio is consistent with an abundance ratio of 3, expected from the spin statistics. The NH2D/NH3 abundance ratio may be ∼1. In general, the data hint at a compact cold gravitationally stable dense core within the warm environment, which may represent pristine material. However this picture still needs a verification with observations at a higher angular resolution.

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Cite

BibTeXRIS
BibTeX
@misc{trofimova2026compact,
  title = {{A compact NH$_2$D source without NH$_3$ counterpart in the S187 high-mass star-forming region}},
  author = {E. A. Trofimova and I. I. Zinchenko and C. Henkel and A. G. Pazukhin and A. F. Punanova and P. M. Zemlyanukha},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2610.40219},
  eprint = {2610.40219},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2610.40219},
}
RIS
TY  - UNPB
TI  - A compact NH_2D source without NH_3 counterpart in the S187 high-mass star-forming region
AU  - E. A. Trofimova
AU  - I. I. Zinchenko
AU  - C. Henkel
AU  - A. G. Pazukhin
AU  - A. F. Punanova
AU  - P. M. Zemlyanukha
PY  - 2026
DA  - 2026/10/29
PB  - arXiv
DO  - 10.48550/arxiv.2610.40219
UR  - https://arxiv.org/abs/2610.40219
AB  - Our goal is to investigate a so far only tentatively detected compact NH_2D source devoid of a notable NH_3 counterpart, located rather close to the luminous IRAS 01202+6133 source (the projected distance is ≲0.3 pc) in the S187 high-mass star-forming region. A high ammonia deuteration in such an environment is unusual. We performed observations of this area with the 20-m OSO radio telescope in several frequency ranges from ∼72 to ∼112 GHz. The area was mapped at the lower frequencies while at the higher frequencies only the position of the NH_2D emission peak was observed. The data were analyzed using non-LTE modeling. The data confirm a compact NH_2D source with a size of ≲0.2 pc. In addition, emission from about 20 molecules was detected, but only the DCO^+(1-0) peak coincides with the NH_2D clump. The clump is not associated with any known astronomical source or an NH_3 emission peak but the dust continuum map shows an enhancement at approximately the same position. The gas kinetic temperature derived from various indicators is ∼20-30 K, which possibly characterizes the surrounding material. The intrinsic NH_2D line width (∼0.4 km/s) implies a clump with subsonic or transonic turbulence. The ortho/para NH_2D line intensity ratio is consistent with an abundance ratio of 3, expected from the spin statistics. The NH_2D/NH_3 abundance ratio may be ∼1. In general, the data hint at a compact cold gravitationally stable dense core within the warm environment, which may represent pristine material. However this picture still needs a verification with observations at a higher angular resolution.
ER  -