Investigating the role of magnetic fields in star formation using molecular line profiles

Abstract

Determining the importance of magnetic fields in star forming environments is hampered by the difficulty of accurately measuring both field strength and gas properties in molecular clouds. We post-process three-dimensional non-ideal magnetohydrodynamic simulations of prestellar cores with a time-dependent chemical network, and use radiative transfer modelling to calculate self-consistent molecular line profiles. Varying the initial mass-to-flux ratio from sub- to super-critical results in significant changes to both the intensity and shape of several observationally important molecular lines. We identify the peak intensity ratio of N${}_2$H${}^{+}$ to CS lines, and the CS $J=2-1$ blue-to-red peak intensity ratio, as promising diagnostics of the initial mass-to-flux ratio, with N${}_2$H${}^{+}$/CS values of $>0.6$ ($<0.2$) and CS blue/red values of $<3$ ($>5$) indicating subcritical (supercritial) collapse. These criteria suggest that, despite presently being magnetically supercritical, L1498 formed from subcritical initial conditions.

arXiv comment8 pages of text, 10 pages in total. Accepted in MNRAS

References in corpus (28)

• An atomic and molecular database for analysis of submillimetre line observations
• The UMIST database for astrochemistry 2012
• SPLASH: An interactive visualisation tool for Smoothed Particle Hydrodynamics simulations
• Systematic Molecular Differentiation in Starless Cores
• Phantom: A smoothed particle hydrodynamics and magnetohydrodynamics code for astrophysics
• Astrochemistry and compositions of planetary systems
• LIME - a flexible, non-LTE line excitation and radiation transfer method for millimeter and far-infrared wavelengths
• On the internal structure of starless cores. II. A molecular survey of L1498 and L1517B
• Collapse of a molecular cloud core to stellar densities: stellar core and outflow formation in radiation magnetohydrodynamics simulations
• UCLCHEM: A Gas-Grain Chemical Code
• Testing Magnetic Star Formation Theory
• Ambipolar-Diffusion Timescale, Star-Formation Timescale, and the Ages of Molecular Clouds: Is There a Discrepancy?
• Magnetic fields towards Ophiuchus-B derived from SCUBA-2 polarization measurements
• The collapse of a molecular cloud core to stellar densities using radiation non-ideal magnetohydrodynamics
• Gas-phase CO depletion and N2H+ abundances in starless cores
• ALMA resolves the hourglass magnetic field in G31.41+0.31
• SCUBA polarisation observations of the magnetic fields in the prestellar cores L1498 and L1517B
• Magnetic fields in the infrared dark cloud G34.43+0.24
• NICIL: A stand alone library to self-consistently calculate non-ideal magnetohydrodynamic coefficients in molecular cloud cores
• Non-Equilibrium Chemistry of Dynamically Evolving Prestellar Cores: I. Basic Magnetic and Non-Magnetic Models and Parameter Studies
• Chemical evolution during the formation of a protoplanetary disk
• Physical and chemical modeling of the starless core L1512
• Non-Equilibrium Chemistry of Dynamically Evolving Prestellar Cores: II. Ionization and Magnetic Field
• Different Modes of Star Formation: Gravitational Collapse of Magnetically Subcritical Cloud
• Timescales for Low-Mass Star Formation in Extragalactic Environments: Implications for the Stellar IMF
• An efficient method for determining the chemical evolution of gravitationally collapsing prestellar cores
• Ambipolar diffusion and the molecular abundances in prestellar cores
• Effect of OH depletion on measurements of the mass-to-flux ratio in molecular cloud cores

Cited by in corpus (7)

• Non-ideal MHD simulations of subcritical prestellar cores with non-equilibrium chemistry
• Can we observe the ion-neutral drift velocity in prestellar cores?
• The initial magnetic criticality of prestellar cores
• Insights into the first and second hydrostatic core stages from numerical simulations
• Differences in chemical evolution between isolated and embedded prestellar cores
• Line emission from filaments in molecular clouds
• Deuterium fractionation of the starless core L 1498