Deuterium fractionation and H2D+ evolution in turbulent and magnetized cloud cores

Abstract

High-mass stars are expected to form from dense prestellar cores. Their precise formation conditions are widely discussed, including their virial condition, which results in slow collapse for super-virial cores with strong support by turbulence or magnetic fields, or fast collapse for sub-virial sources. To disentangle their formation processes, measurements of the deuterium fractions are frequently employed to approximately estimate the ages of these cores and to obtain constraints on their dynamical evolution. We here present 3D magneto-hydrodynamical simulations including for the first time an accurate non-equilibrium chemical network with 21 gas-phase species plus dust grains and 213 reactions. With this network we model the deuteration process in fully depleted prestellar cores in great detail and determine its response to variations in the initial conditions. We explore the dependence on the initial gas column density, the turbulent Mach number, the mass-to-magnetic flux ratio and the distribution of the magnetic field, as well as the initial ortho-to-para ratio of H2. We find excellent agreement with recent observations of deuterium fractions in quiescent sources. Our results show that deuteration is rather efficient, even when assuming a conservative ortho-to-para ratio of 3 and highly sub-virial initial conditions, leading to large deuterium fractions already within roughly a free-fall time. We discuss the implications of our results and give an outlook to relevant future investigations.

submitted to MNRAS, 26 pages, 15 figures, comments welcome

References in corpus (27)

• Cold Dark Clouds: The Initial Conditions for Star Formation
• Modeling Collapse and Accretion in Turbulent Gas Clouds: Implementation and Comparison of Sink Particles in AMR and SPH
• Three-dimensional simulation of massive star formation in the disk accretion scenario
• The link between turbulence, magnetic fields, filaments, and star formation in the Central Molecular Zone cloud G0.253+0.016
• Fragmentation of Molecular Clumps and Formation of Protocluster
• A robust numerical scheme for highly compressible magnetohydrodynamics: Nonlinear stability, implementation and tests
• Gravitational fragmentation and the formation of brown dwarfs in stellar clusters
• Survey of ortho-H2D+(1_{1,0}-1_{1,1}) in dense cloud cores
• On the frequency of N2H+ and N2D+
• An Unstable Truth: How Massive Stars get their Mass
• ATLASGAL-selected massive clumps in the inner Galaxy: I. CO depletion and isotopic ratios
• Benchmarking spin-state chemistry in starless core models
• The Distribution of Ortho-H_2D+(1_1,0 - 1_1,1) in L1544: Tracing the Deuteration Factory in Prestellar Cores
• Searching for massive pre--stellar cores through observations of N2H+ and N2D+
• A UV flux constraint on the formation of direct collapse black holes
• Three-fluid plasmas in star formation II. Momentum transfer rate coefficients
• Deuteration and evolution in the massive star formation process: the role of surface chemistry
• Dense core properties in the Infrared Dark cloud G14.225-0.506 revealed by ALMA
• The influence of magnetic fields on the thermodynamics of primordial star formation
• Chemical evolution in the early phases of massive star formation II: Deuteration
• Three-fluid plasmas in star formation I. Magneto-hydrodynamic equations
• Revealing H2D+ depletion and compact structure in starless and protostellar cores with ALMA
• The Lifetimes of Phases in High-Mass Star-Forming Regions
• Formation of carbon-enhanced metal-poor stars in the presence of far ultraviolet radiation
• Detection of H2D+ in a massive prestellar core in Orion B
• The location, clustering, and propagation of massive star formation in giant molecular clouds
• Structure, Dynamics and Deuterium Fractionation of Massive Pre-Stellar Cores

Cited by in corpus (21)

• Survey of ortho-H${}_2$D${}^{+}$ in high-mass star-forming regions
• The effect of non-equilibrium metal cooling on the interstellar medium
• The formation of protostellar binaries in primordial minihalos
• On the size of the CO-depletion radius in the IRDC G351.77-0.51
• The 3D structure of CO depletion in high-mass prestellar regions
• Magnetic tension and instabilities in the Orion A integral shaped filament
• A timeline for massive star-forming regions via combined observation of o-H${}_2$D${}^{+}$ and N${}_2$D${}^{+}$
• Physical and chemical modeling of the starless core L1512
• ATLASGAL -- selected massive clumps in the inner Galaxy. IX. Deuteration of ammonia
• Fast deuterium fractionation in magnetized and turbulent filaments
• The Cygnus Allscale Survey of Chemistry and Dynamical Environments: CASCADE: Overview and first results toward DR20 from the Max Planck IRAM Observatory program (MIOP)
• H${}_2$ ortho-to-para conversion on grains: A route to fast deuterium fractionation in dense cloud cores?
• Chemical post-processing of magneto-hydrodynamical simulations of star-forming regions: robustness and pitfalls
• Dynamical Ejections of Stars due to an Accelerating Gas Filament
• Deuterium Chemodynamics of Massive Pre-Stellar Cores
• Non-ideal magnetohydrodynamics of self-gravitating filaments
• Dust evolution in pre-stellar cores
• Gas phase Elemental abundances in Molecular cloudS (GEMS). X. Observational effects of turbulence on the chemistry of molecular clouds
• Deuterium fractionation of the starless core L 1498
• Fire from Ice - Massive Star Birth from Infrared Dark Clouds
• Synthetic observations using POLARIS: an application to simulations of massive prestellar cores