Cosmic Ray Feedback in Galactic Disks: Star Formation, Cosmic Ray Transport, and Multiphase Outflows in TIGRESS++ Simulations

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Hauptverfasser: Kim, Chang-Goo, Armillotta, Lucia, Ostriker, Eve C., Moon, Sanghyuk, Lancaster, Lachlan, Kim, Jeong-Gyu, Linzer, Nora B., Hix, Ronan N.
Format: Preprint
Veröffentlicht: 2026
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author Kim, Chang-Goo
Armillotta, Lucia
Ostriker, Eve C.
Moon, Sanghyuk
Lancaster, Lachlan
Kim, Jeong-Gyu
Linzer, Nora B.
Hix, Ronan N.
author_facet Kim, Chang-Goo
Armillotta, Lucia
Ostriker, Eve C.
Moon, Sanghyuk
Lancaster, Lachlan
Kim, Jeong-Gyu
Linzer, Nora B.
Hix, Ronan N.
contents We present new simulations of local star-forming disks that self-consistently evolve cosmic rays (CRs) and multiphase gas using TIGRESS++. To isolate the role of CRs, we conduct paired simulations under solar-neighborhood conditions: a magnetohydrodynamics (MHD) model following the standard TIGRESS-classic framework with FUV heating and supernova (SN) feedback from star clusters formed via gravitational collapse; and a CRMHD model in which an additional 10% of each SN's energy is injected as CRs. These CRs are transported anisotropically along magnetic field lines via a two-moment solver, with the CR scattering rate set by balancing Alfven-wave growth and damping based on the self-confinement paradigm. The CRMHD model develops a characteristic two-zone vertical CR profile: uniform pressure in the diffusion-dominated, high-density midplane gas, and an exponential atmosphere shaped primarily by advection and streaming in low-density extraplanar gas. The CR pressure is comparable to the total thermal gas pressure in the midplane, but is too uniform to affect gas dynamics, leaving SFRs unchanged. In contrast, the vertical CR pressure gradient at |z| > 1 kpc accelerates warm outflowing gas, resulting in an approximately 4 times higher mass loading factor than in the MHD model. CR-gas interactions increase CR energy near the midplane through compressional work, while CR streaming heats low-density warm-hot gas. TIGRESS++ opens a path toward investigating CR transport and CR-regulated ISM and outflow dynamics at high resolution across diverse galactic environments.
format Preprint
id arxiv_https___arxiv_org_abs_2605_26238
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Cosmic Ray Feedback in Galactic Disks: Star Formation, Cosmic Ray Transport, and Multiphase Outflows in TIGRESS++ Simulations
Kim, Chang-Goo
Armillotta, Lucia
Ostriker, Eve C.
Moon, Sanghyuk
Lancaster, Lachlan
Kim, Jeong-Gyu
Linzer, Nora B.
Hix, Ronan N.
Astrophysics of Galaxies
We present new simulations of local star-forming disks that self-consistently evolve cosmic rays (CRs) and multiphase gas using TIGRESS++. To isolate the role of CRs, we conduct paired simulations under solar-neighborhood conditions: a magnetohydrodynamics (MHD) model following the standard TIGRESS-classic framework with FUV heating and supernova (SN) feedback from star clusters formed via gravitational collapse; and a CRMHD model in which an additional 10% of each SN's energy is injected as CRs. These CRs are transported anisotropically along magnetic field lines via a two-moment solver, with the CR scattering rate set by balancing Alfven-wave growth and damping based on the self-confinement paradigm. The CRMHD model develops a characteristic two-zone vertical CR profile: uniform pressure in the diffusion-dominated, high-density midplane gas, and an exponential atmosphere shaped primarily by advection and streaming in low-density extraplanar gas. The CR pressure is comparable to the total thermal gas pressure in the midplane, but is too uniform to affect gas dynamics, leaving SFRs unchanged. In contrast, the vertical CR pressure gradient at |z| > 1 kpc accelerates warm outflowing gas, resulting in an approximately 4 times higher mass loading factor than in the MHD model. CR-gas interactions increase CR energy near the midplane through compressional work, while CR streaming heats low-density warm-hot gas. TIGRESS++ opens a path toward investigating CR transport and CR-regulated ISM and outflow dynamics at high resolution across diverse galactic environments.
title Cosmic Ray Feedback in Galactic Disks: Star Formation, Cosmic Ray Transport, and Multiphase Outflows in TIGRESS++ Simulations
topic Astrophysics of Galaxies
url https://arxiv.org/abs/2605.26238