Ambipolar diffusion and the molecular abundances in prestellar cores

Abstract

We investigate differences in the molecular abundances between magnetically super- and sub-critical prestellar cores, performing three-dimensional non-ideal magnetohydrodynamical (MHD) simulations with varying densities and magnetic field strengths, and post-processing the results with a time-dependent gas-grain chemical code. Most molecular species show significantly more central depletion in subcritical models, due to the longer duration of collapse. However, the directly observable quantities - the molecule to hydrogen column density ratios - are generally too similar for observational data to discriminate between models. The profiles of N${}_2$H${}^{+}$ and HCO${}^{+}$ show qualitative differences between supercritical and subcritical models on scales of $0.01\mathrm{pc}$, which may allow the two cases to be distinguished. However, this requires knowledge of the hydrogen column density, which is not directly measureable, and predicted line intensity profiles from radiative transfer modelling are similar for these molecules. Other commonly observed species, such as HCN and CH${}_3$OH, have line intensity profiles which differ more strongly between models, and so are more promising as tracers of the mechanism of cloud collapse.

arXiv comment8 pages, 11 figures. MNRAS accepted 05/07/19

References in corpus (31)

• A computer program for fast non-LTE analysis of interstellar line spectra
• Cold Dark Clouds: The Initial Conditions for Star Formation
• The UMIST database for astrochemistry 2012
• Systematic Molecular Differentiation in Starless Cores
• Phantom: A smoothed particle hydrodynamics and magnetohydrodynamics code for astrophysics
• Molecular Inventories and Chemical Evolution of Low-mass Protostellar Envelopes
• Molecular Evolution in Collapsing Prestellar Cores
• Molecular Evolution in Collapsing Prestellar Cores III: Contraction of A Bonnor-Ebert Sphere
• On the internal structure of starless cores. II. A molecular survey of L1498 and L1517B
• Radiation Magnetohydrodynamic Simulations of Protostellar Collapse: Non-Ideal Magnetohydrodynamic Effects and Early Formation of Circumstellar Disks
• The effect of uncertainties on chemical models of dark clouds
• Can non-ideal magnetohydrodynamics solve the magnetic braking catastrophe?
• UCLCHEM: A Gas-Grain Chemical Code
• Effects of Ohmic and ambipolar diffusion on the formation and evolution of the first cores, protostars and circumstellar discs
• Bimodality of circumstellar disk evolution induced by Hall current
• Molecular Evolution in Collapsing Prestellar Cores II: The Effect of Grain-surface Reactions
• Chemical modelling of complex organic molecules with peptide-like bonds in star-forming regions
• Protostellar birth with ambipolar and ohmic diffusion
• The impact of the Hall effect during cloud core collapse:implications for circumstellar disk evolution
• The collapse of a molecular cloud core to stellar densities using radiation non-ideal magnetohydrodynamics
• Protostar Formation in Supersonic Flows: Growth and Collapse of Spherical Cores
• A Coupled Dynamical and Chemical Model of Starless Cores of Magnetized Molecular Clouds: I. Formulation and Initial Results
• Survival of interstellar molecules to prestellar dense core collapse and early phases of disk formation
• Chemical and physical characterization of collapsing low-mass prestellar dense cores
• NICIL: A stand alone library to self-consistently calculate non-ideal magnetohydrodynamic coefficients in molecular cloud cores
• The impact of non-ideal magnetohydrodynamics on binary star formation
• Hall effect-driven formation of gravitationally unstable discs in magnetized molecular cloud cores
• On the origin of magnetic fields in stars
• Non-Equilibrium Chemistry of Dynamically Evolving Prestellar Cores: I. Basic Magnetic and Non-Magnetic Models and Parameter Studies
• An efficient method for determining the chemical evolution of gravitationally collapsing prestellar cores
• Young starless cores embedded in the magnetically dominated Pipe Nebula. II. Extended dataset

Cited by in corpus (11)

• Do we need non-ideal magnetohydrodynamics to model protostellar discs?
• Non-ideal MHD simulations of subcritical prestellar cores with non-equilibrium chemistry
• The widths of magnetised filaments in molecular clouds
• Investigating the role of magnetic fields in star formation using molecular line profiles
• Chemistry and dynamics of the prestellar core L1544
• Chemical post-processing of magneto-hydrodynamical simulations of star-forming regions: robustness and pitfalls
• Synthetic line and continuum observations of simulated turbulent clouds: the apparent widths of filaments
• The initial magnetic criticality of prestellar cores
• Insights into the first and second hydrostatic core stages from numerical simulations
• Some Aspects of Rotation and Magnetic Field Morphology in the Infrared Dark Cloud G34.43+00.24
• Unveiling Fiber Networks and Core Formation in the DR21 South Filament