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Abstract We use hydrodynamical simulations of two Milky Way–mass galaxies to demonstrate the impact of cosmic-ray pressure on the kinematics of cool and warm circumgalactic gas. Consistent with previous studies, we find that cosmic-ray pressure can dominate over thermal pressure in the inner 50 kpc of the circumgalactic medium (CGM), creating an overall cooler CGM than that of similar galaxy simulations run without cosmic rays. We generate synthetic sight lines of the simulated galaxies’ CGM and use Voigt profile-fitting methods to extract ion column densities, Doppler-bparameters, and velocity centroids of individual absorbers. We directly compare these synthetic spectral line fits with HST/COS CGM absorption-line data analyses, which tend to show that metallic species with a wide range of ionization potential energies are often kinematically aligned. Compared to the Milky Way simulation run without cosmic rays, the presence of cosmic-ray pressure in the inner CGM creates narrower Oviabsorption features and broader Siiiiabsorption features, a quality that is more consistent with observational data. Additionally, because the cool gas is buoyant due to nonthermal cosmic-ray pressure support, the velocity centroids of both cool and warm gas tend to align in the simulated Milky Way with feedback from cosmic rays. Our study demonstrates that detailed, direct comparisons between simulations and observations, focused on gas kinematics, have the potential to reveal the dominant physical mechanisms that shape the CGM.
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This content will become publicly available on December 1, 2025
Observational Signatures of AGN Feedback in the Morphology and the Ionization States of Milky Way-like Galaxies
Abstract We make an in-depth analysis of different active galactic nuclei (AGN) jet models’ signatures, inducing quiescence in galaxies with a halo mass of 1012M⊙. Three jet models, including cosmic-ray-dominant, hot thermal, and precessing kinetic jets, are studied at two energy flux levels each, compared to a jet-free, stellar feedback-only simulation. Each of our simulations is idealized isolated galaxy simulations with AGN jet powers that are constant in time and generated using GIZMO and with FIRE stellar feedback. We examine the distribution of Mgii, Ovi, and Oviiiions, alongside gas temperature and density profiles. Low-energy ions, like Mgii, concentrate in the interstellar medium (ISM), while higher energy ions, e.g., Oviii, prevail at the AGN jet cocoon’s edge. High-energy flux jets display an isotropic ion distribution with lower overall density. High-energy thermal or cosmic-ray jets pressurize at smaller radii, significantly suppressing core density. The cosmic-ray jet provides extra pressure support, extending cool and warm gas distribution. A break in the ion-to-mass ratio slope in Oviand Oviiiis demonstrated in the ISM-to-circumgalactic medium (CGM) transition (between 10 and 30 kpc), growing smoothly toward the CGM at greater distances.
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- PAR ID:
- 10561809
- Author(s) / Creator(s):
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Publisher / Repository:
- IOP Publishing
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 977
- Issue:
- 1
- ISSN:
- 0004-637X
- Page Range / eLocation ID:
- 72
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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