Abstract
ABSTRACT Non-ideal magnetohydrodynamic (MHD) processes – namely Ohmic resistivity, ambipolar diffusion, and the Hall effect – modify the early stages of the star formation process and the surrounding environment. Collectively, they have been shown to promote disc formation and promote or hinder outflows. But which non-ideal process has the greatest impact? Using three-dimensional smoothed particle radiation non-ideal MHD simulations, we model the gravitational collapse of a rotating, magnetized cloud through the first hydrostatic core phase to shortly after the formation of the stellar core. We investigate the impact of each process individually and collectively. Including any non-ideal process decreases the maximum magnetic field strength by at least an order of magnitude during the first core phase compared to using ideal MHD, and promotes the formation of a magnetic wall. When the magnetic field and rotation vectors are anti-aligned and the Hall effect is included, rotationally supported discs of r ≳ 20 au form; when only the Hall effect is included and the vectors are aligned, a counter-rotating pseudo-disc forms that is not rotationally supported. Rotationally supported discs of r ≲ 4 au form if only Ohmic resistivity or ambipolar diffusion are included. The Hall effect suppresses first core outflows when the vectors are anti-aligned and suppresses stellar core outflows independent of alignment. Ohmic resistivity and ambipolar diffusion each promote first core outflows and delay the launching of stellar core outflows. Although each non-ideal process influences star formation, these results suggest that the Hall effect has the greatest influence.
Highlights
Discs and outflows are common signatures of young, low-mass stars
Using 3D smoothed particle radiation magnetohydrodynamic simulations, we model the gravitational collapse of a molecular cloud core through the first and stellar core phases in a magnetised medium
We follow the gravitational collapse of the cloud core through the first hydrostatic core phase (10−12 ρmax/(g cm−3) 10−8) and through the second collapse phase (10−8 ρmax/(g cm−3) 10−4) to the formation of the stellar core
Summary
Discs and outflows are common signatures of young, low-mass stars. For reviews, see Bachiller (1996), Williams & Cieza (2011) and Bally (2016).Recent studies and surveys have have shown that discs vary in size, dust content, morphology and even by region (e.g. Tobin et al 2015, 2020; Pinte et al 2016; Ansdell et al 2016, 2017, 2018; Birnstiel et al 2018; Andersen et al 2019; Loomis et al 2020; Hendler et al 2020). Discs and outflows are common signatures of young, low-mass stars. Rao et al 2014; Stephens et al 2014, 2017; Harris et al 2018), interpreting the magnetic field geometry is challenging since it is typically inferred from dust polarisation and magnetic fields are not the only processes to polarise dust (e.g. Kataoka et al 2015, 2017). Discs are common, but their characteristics are heavily influenced by their environment. Outflows are common from young stars when the accretion process is still active
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
