• DOI:10.1051/0004-6361/201937012
• Corpus ID: 235652375

Singly- and doubly-deuterated formaldehyde in massive star-forming regions

@inproceedings{Zahorecz2021SinglyAD,
  title={Singly- and doubly-deuterated formaldehyde in massive star-forming regions},
  author={Sarolta Zahorecz and Izaskun J{\'i}menez-Serra and Leonardo Testi and Katharina Immer and Francesco Fontani and Paola Caselli and K. Wang and Toshikazu Onishi},
  year={2021}
}

• S. Zahorecz, I. Jímenez-Serra, +5 authors T. Onishi
• Published 25 June 2021
• Physics

Context. Deuterated molecules are good tracers of the evolutionary stage of star-forming cores. During the star formation process, deuterated molecules are expected to be enhanced in cold, dense pre-stellar cores and to deplete after protostellar birth. Aims. In this paper, we study the deuteration fraction of formaldehyde in high-mass star-forming cores at different evolutionary stages to investigate whether the deuteration fraction of formaldehyde can be used as an evolutionary tracer. Methods. Using the APEX SEPIA Band 5 receiver, we extended our pilot study of the J = 3 → 2 rotational lines of HDCO and D 2 CO to eleven high-mass star-forming regions that host objects at different evolutionary stages. High-resolution follow-up observations of eight objects in ALMA Band6 were performed to reveal the size of the H 2 CO emission and to give an estimate of the deuteration fractions HDCO/H 2 CO and D 2 CO/HDCO at scales of ∼ 6 (cid:48)(cid:48) (0.04–0.15pc at the distance of our targets). Results. Our observations show that singly and doubly deuterated H 2 CO are detected towards high-mass protostellar objects (HMPOs) and ultracompact H II regions (UC H II regions), and the deuteration fraction of H 2 CO is also found to decrease by an order of magnitude from the earlier HMPO phases to the latest evolutionary stage (UC H II ), from ∼ 0.13 to ∼ 0.01. We have not detected HDCO and D 2 CO emission from the youngest sources (i.e. high-mass starless cores or HMSCs). Conclusions. Our extended study supports the results of the previous pilot study: the deuteration fraction of formaldehyde decreases with the evolutionary stage, but higher sensitivity observations are needed to provide more stringent constraints on the D/H ratio during the HMSC phase. The calculated upper limits for the HMSC sources are high, so the trend between HMSC and HMPO phases cannot be constrained.