Brown Dwarf Formation Through Gravitational Collapse: Insights From 3D Numerical Simulations

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Main Authors: Ahmad, Adnan Ali, Commerçon, Benoît, Chabrier, Gilles, Borderies, Antonin
Format: Preprint
Published: 2025
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author Ahmad, Adnan Ali
Commerçon, Benoît
Chabrier, Gilles
Borderies, Antonin
author_facet Ahmad, Adnan Ali
Commerçon, Benoît
Chabrier, Gilles
Borderies, Antonin
contents The formation mechanism of Brown Dwarfs (BDs), whether akin to stars or ejected planetary-mass objects, remains debated. We present the first 3D radiation-MHD simulations of magnetized, turbulent, gravitationally unstable low-mass cores ($0.05-0.1\ \mathrm{M_{\odot}}$) collapsing into proto-BDs. Using the {\ttfamily RAMSES} code with adaptive mesh refinement, we model the full dynamical range ($10^{5}~-10^{22}\ \mathrm{cm^{-3}}$), including radiative transfer (flux limited diffusion) and non-ideal MHD (ambipolar diffusion). Our simulations self-consistently follow the isothermal collapse, first hydrostatic core formation, H$_{2}$ dissociation, and BD birth. The resulting BDs have initial radii $\approx 0.75\ \mathrm{R_{\odot}}$ and masses $\approx 0.8\ \mathrm{M_{Jup}}$, growing via accretion as we follow the early evolution of the object. Crucially, we find that BDs may form similarly to low-mass stars but with a prolonged first-core phase, supporting a star-like formation scenario.
format Preprint
id arxiv_https___arxiv_org_abs_2509_12336
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Brown Dwarf Formation Through Gravitational Collapse: Insights From 3D Numerical Simulations
Ahmad, Adnan Ali
Commerçon, Benoît
Chabrier, Gilles
Borderies, Antonin
Solar and Stellar Astrophysics
Astrophysics of Galaxies
The formation mechanism of Brown Dwarfs (BDs), whether akin to stars or ejected planetary-mass objects, remains debated. We present the first 3D radiation-MHD simulations of magnetized, turbulent, gravitationally unstable low-mass cores ($0.05-0.1\ \mathrm{M_{\odot}}$) collapsing into proto-BDs. Using the {\ttfamily RAMSES} code with adaptive mesh refinement, we model the full dynamical range ($10^{5}~-10^{22}\ \mathrm{cm^{-3}}$), including radiative transfer (flux limited diffusion) and non-ideal MHD (ambipolar diffusion). Our simulations self-consistently follow the isothermal collapse, first hydrostatic core formation, H$_{2}$ dissociation, and BD birth. The resulting BDs have initial radii $\approx 0.75\ \mathrm{R_{\odot}}$ and masses $\approx 0.8\ \mathrm{M_{Jup}}$, growing via accretion as we follow the early evolution of the object. Crucially, we find that BDs may form similarly to low-mass stars but with a prolonged first-core phase, supporting a star-like formation scenario.
title Brown Dwarf Formation Through Gravitational Collapse: Insights From 3D Numerical Simulations
topic Solar and Stellar Astrophysics
Astrophysics of Galaxies
url https://arxiv.org/abs/2509.12336