High NH2D/NH3 ratios in protostellar cores

  title={High NH2D/NH3 ratios in protostellar cores},
  author={J. Hatchell},
  journal={Astronomy and Astrophysics},
  • J. Hatchell
  • Published 2003
  • Physics
  • Astronomy and Astrophysics
Observations of low mass protostars which probe small enough size scales to be within likely CO depletion regions show the highest [NH 2 D]/[NH 3 ] ratios yet measured, of 4-33%. These molecular D/H ratios are higher than those measured on larger scales, showing that deuterium fractionation increases towards protostellar cores. As in cold clouds, such high ratios can be produced by gas-phase ion-molecule chemistry in the presence of depletion. Grain surface chemistry is less likely to explain… Expand
Enhanced Deuterium Fractionation in Dense Interstellar Cores Resulting from Multiply Deuterated H3
In this Letter, we present the first results from updated models of interstellar deuterium chemistry that now include all possible deuterated isotopomers of H. We find that in regions of high densityExpand
Molecular D/H Ratios in the Dense Gas Surrounding Low-Mass Protostars
Abstract Observations of [HDCO]/[H 2 CO] and [DCN]/[HCN] ratios have been made towards a selection of low-mass protostellar cores in three different star forming regions. Most [HDCO]/ [H 2 CO] ratiosExpand
Searching for massive pre--stellar cores through observations of N2H+ and N2D+
We have measured the deuterium fractionation (through the column density ratio N(N2D+)/N(N2H+)) and the CO depletion factor (ratio between expected and observed CO abundance) in a sample of 10Expand
Probing the initial conditions of high mass star formation: I. Deuteration and depletion in high mass pre/protocluster clumps
Aims. UltraCompact Hit regions are signposts of high-mass star formation. Since high-mass star formation occurs in clusters, one expects to find even earlier phases of massive star formation in theExpand
A survey of [ D2CO] /[ H2CO] and [ N2D^+] /[ N2H^+] ratios towards protostellar cores
Aims. We use observations and models of molecular D/H ratios to probe the physical conditions and chemical history of the gas and to differentiate between gas-phase and grain-surface chemicalExpand
The N 2 D + /N 2 H + ratio as an evolutionary tracer of Class 0 protostars. ⋆
Context. Deuterated ions, especially H2D + and N2D + , are abundant in cold (∼ 10 K), dense (∼ 10 5 cm −3 ) regions, in which CO is frozen out onto dust grains. In such environments, the N2D + /N2H +Expand
We present a survey of 28 molecular outflows driven by low-mass protostars, all of which are sufficiently isolated spatially and/or kinematically to fully separate into individual outflows. Using aExpand
ATLASGAL-selected massive clumps in the inner Galaxy
Context. Deuteration has been used as a tracer of the evolutionary phases of lowand high-mass star formation. The APEX Telescope Large Area Survey (ATLASGAL) provides an important repository for aExpand
Probing the initial conditions of high-mass star formation
  • Chuan-Peng Zhang, Guang-Xing Li, +4 authors M. Pestalozzi
  • Physics
  • 2011
Most work on high-mass star formation has focused on observations of young massive stars in protoclusters. Very little i s known about the preceding stage. Here, we present a new high-resolutionExpand
Statistical modelling of NH+/ND+ + H2/HD/D2 branching ratios.
It is determined that in all cases where both hydrogen and deuterium are present, the NHD(+) product is preferred. Expand


Deuterated Ammonia in Galactic Protostellar Cores
We report on a survey of NH2D toward protostellar cores in low-mass star formation and quiescent regions in the Galaxy. Twenty-three out of thirty-two observed sources have significant (5 σ) NH2DExpand
Gas-Phase Production of NHD2 in L134N
We show analytically that large abundances of NH2D and NHD2 can be produced by gas-phase chemistry in the interiors of cold dense clouds. The calculated fractionation ratios are in good agreementExpand
The Ionization Fraction in Dense Molecular Gas. I. Low-Mass Cores
Observations of C18O, H13CO+, and DCO+ toward 23 low-mass cores are used to constrain the fractional ionization (electron abundance) within them. Chemical models have been run over a wide range ofExpand
We present evidence for CO depletion toward the starless cloud core L1544. A comparison between C17O and the 1.3 mm continuum dust emission shows that CO is depleted by a factor of ~10 at the dustExpand
A survey of (HDCO)/(H2CO) and (DCN)/(HCN) ratios towards low-mass protostellar cores
We present observations of [HDCO]/[H 2 CO] and [DCN]/[HCN] ratios towards a selection of low-mass protostellar cores in three different star forming regions. The best fit to the observed [HDCO]/[H 2Expand
High-velocity hot ammonia in bipolar outflows
We have detected high-velocity ammonia emission associated with four bipolar molecular outflows excited by young stars (L1157, L1448, IRAS 3282, and NGC 2071). The high-velocity emission is moreExpand
Deuterated Methanol in the Orion Compact Ridge
We have investigated the chemistry of hot cores containing methanol, formaldehyde, and their deuterated forms. We have computed the D fractionation ratios attainable by the addition of H and D atomsExpand
Observations of NH2D toward Dark Molecular Clouds
The 1-1 transition of NH2D at 110.1536 GHz was surveyed toward 16 cores of high ammonia abundance in 14 cold dark clouds and was detected toward eight cloud cores, L1448, B1, L1489N, L1551N, L1641N,Expand
Triply deuterated ammonia in NGC 1333
The Caltech Submillimeter Observatory has detected triply deuterated ammonia, ND3, through its JK =1 a! 0 s transition near 310 GHz. Emission is found in the NGC 1333 region, both towards IRAS 4A andExpand
The puzzling detection of D_2CO in the molecular cloud L1689N
We present new observations of the D_2CO emission towards the small cloud L1689N in the ρ Ophiuchus complex. We surveyed five positions, three being a cut across a shock site and two probing theExpand