Singly- and doubly-deuterated formaldehyde in massive star-forming regions. (arXiv:2106.13433v2 [astro-ph.GA] UPDATED)

Singly- and doubly-deuterated formaldehyde in massive star-forming regions. (arXiv:2106.13433v2 [astro-ph.GA] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Zahorecz_S/0/1/0/all/0/1">S. Zahorecz</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jimenez_Serra_I/0/1/0/all/0/1">I. Jimenez-Serra</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Testi_L/0/1/0/all/0/1">L. Testi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Immer_K/0/1/0/all/0/1">K. Immer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fontani_F/0/1/0/all/0/1">F. Fontani</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Caselli_P/0/1/0/all/0/1">P. Caselli</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wang_K/0/1/0/all/0/1">K. Wang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Onishi_T/0/1/0/all/0/1">T. Onishi</a>

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. 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. Using the APEX SEPIA Band 5 receiver, we extended our
pilot study of the $J$=3$rightarrow$2 rotational lines of HDCO and D$_2$CO to
eleven high-mass star-forming regions that host objects at different
evolutionary stages. High-resolution follow-up observations of eight objects in
ALMA Band 6 were performed to reveal the size of the H$_2$CO emission and to
give an estimate of the deuteration fractions HDCO/H$_2$CO and D$_2$CO/HDCO at
scales of $sim$6″ (0.04-0.15 pc at the distance of our targets). Our
observations show that singly- and doubly deuterated H$_2$CO are detected
toward high-mass protostellar objects (HMPOs) and ultracompact HII regions
(UCHII regions), the deuteration fraction of H$_2$CO is also found to decrease
by an order of magnitude from the earlier HMPO phases to the latest
evolutionary stage (UCHII), from $sim$0.13 to $sim$0.01. We have not detected
HDCO and D$_2$CO emission from the youngest sources (high-mass starless cores,
HMSCs). Our extended study supports the results of the previous pilot study:
the deuteration fraction of formaldehyde decreases with 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.

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. 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. Using the APEX SEPIA Band 5 receiver, we extended our
pilot study of the $J$=3$rightarrow$2 rotational lines of HDCO and D$_2$CO to
eleven high-mass star-forming regions that host objects at different
evolutionary stages. High-resolution follow-up observations of eight objects in
ALMA Band 6 were performed to reveal the size of the H$_2$CO emission and to
give an estimate of the deuteration fractions HDCO/H$_2$CO and D$_2$CO/HDCO at
scales of $sim$6″ (0.04-0.15 pc at the distance of our targets). Our
observations show that singly- and doubly deuterated H$_2$CO are detected
toward high-mass protostellar objects (HMPOs) and ultracompact HII regions
(UCHII regions), the deuteration fraction of H$_2$CO is also found to decrease
by an order of magnitude from the earlier HMPO phases to the latest
evolutionary stage (UCHII), from $sim$0.13 to $sim$0.01. We have not detected
HDCO and D$_2$CO emission from the youngest sources (high-mass starless cores,
HMSCs). Our extended study supports the results of the previous pilot study:
the deuteration fraction of formaldehyde decreases with 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.

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