Resolving the Unresolved Galactic Winds in Multi-phase Models. I. Methodology and Application

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Main Authors: Xu, Xinfeng, Fielding, Drummond, Heckman, Timothy, Bryan, Greg L., Henry, Alaina, Arellano-Cordova, Karla Z., Carr, Cody, Chisholm, John, Faucher-Giguere, Claude-Andre, Hayes, Matthew, Huberty, Mason, Jennings, Michael, Martin, Crystal L., Scarlata, Claudia, Strom, Allison L.
Format: Preprint
Published: 2026
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author Xu, Xinfeng
Fielding, Drummond
Heckman, Timothy
Bryan, Greg L.
Henry, Alaina
Arellano-Cordova, Karla Z.
Carr, Cody
Chisholm, John
Faucher-Giguere, Claude-Andre
Hayes, Matthew
Huberty, Mason
Jennings, Michael
Martin, Crystal L.
Scarlata, Claudia
Strom, Allison L.
author_facet Xu, Xinfeng
Fielding, Drummond
Heckman, Timothy
Bryan, Greg L.
Henry, Alaina
Arellano-Cordova, Karla Z.
Carr, Cody
Chisholm, John
Faucher-Giguere, Claude-Andre
Hayes, Matthew
Huberty, Mason
Jennings, Michael
Martin, Crystal L.
Scarlata, Claudia
Strom, Allison L.
contents Galactic winds shape galaxy evolution; however, the outflowing gas is complex: it consists of multiple ionization phases, and its properties vary spatially. Therefore, methods that combine high-fidelity observations with state-of-the-art galactic-wind models are limited. Here we investigate methods for fitting the column density profiles derived from high-quality outflow observations with the multiphase, multiscale wind model from Fielding & Bryan 2022. We identify three key outflow parameters: the initial hot-phase mass-loading factor ($η_\text{ M,hot,0}$), the initial cool-phase mass-loading factor ($η_\text{ M,cool,0}$), and the initial cool-cloud mass. We obtain good fits for most galaxies, with tight constraints on $η_\text{ M,cool,0}$ and moderate constraints on the other two parameters. We find the inferred $η_\text{ M,cool,0}$ and $η_\text{ M,hot,0}$ are mostly of order unity, with significant scatter. The constraints on $η_\text{ M,hot,0}$ suggest that the interaction between the cool and hot phases allows us to indirectly constrain the properties of the hot wind from cool-outflow observations. The model also predicts various radial trends. First, for all galaxies, the cool-phase outflow velocity increases between $1-2$ times of the half-light radius, then reaches a plateau. Second, most galaxies exhibit increasing $η_\text{ M,cool}$ and decreasing $η_\text{ M,hot}$ with radius, with a few showing the reverse trends. These results are effective, model-conditional constraints, and are consistent with other recent multiphase simulations and observations. This highlights that the velocity-radius mapping encoded in UV absorption profiles enables recovery of outflow spatial structures from spatially integrated spectra. Our method paves the way for future broad parameter studies and guides updates of outflow simulations in future work.
format Preprint
id arxiv_https___arxiv_org_abs_2605_01105
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Resolving the Unresolved Galactic Winds in Multi-phase Models. I. Methodology and Application
Xu, Xinfeng
Fielding, Drummond
Heckman, Timothy
Bryan, Greg L.
Henry, Alaina
Arellano-Cordova, Karla Z.
Carr, Cody
Chisholm, John
Faucher-Giguere, Claude-Andre
Hayes, Matthew
Huberty, Mason
Jennings, Michael
Martin, Crystal L.
Scarlata, Claudia
Strom, Allison L.
Astrophysics of Galaxies
Galactic winds shape galaxy evolution; however, the outflowing gas is complex: it consists of multiple ionization phases, and its properties vary spatially. Therefore, methods that combine high-fidelity observations with state-of-the-art galactic-wind models are limited. Here we investigate methods for fitting the column density profiles derived from high-quality outflow observations with the multiphase, multiscale wind model from Fielding & Bryan 2022. We identify three key outflow parameters: the initial hot-phase mass-loading factor ($η_\text{ M,hot,0}$), the initial cool-phase mass-loading factor ($η_\text{ M,cool,0}$), and the initial cool-cloud mass. We obtain good fits for most galaxies, with tight constraints on $η_\text{ M,cool,0}$ and moderate constraints on the other two parameters. We find the inferred $η_\text{ M,cool,0}$ and $η_\text{ M,hot,0}$ are mostly of order unity, with significant scatter. The constraints on $η_\text{ M,hot,0}$ suggest that the interaction between the cool and hot phases allows us to indirectly constrain the properties of the hot wind from cool-outflow observations. The model also predicts various radial trends. First, for all galaxies, the cool-phase outflow velocity increases between $1-2$ times of the half-light radius, then reaches a plateau. Second, most galaxies exhibit increasing $η_\text{ M,cool}$ and decreasing $η_\text{ M,hot}$ with radius, with a few showing the reverse trends. These results are effective, model-conditional constraints, and are consistent with other recent multiphase simulations and observations. This highlights that the velocity-radius mapping encoded in UV absorption profiles enables recovery of outflow spatial structures from spatially integrated spectra. Our method paves the way for future broad parameter studies and guides updates of outflow simulations in future work.
title Resolving the Unresolved Galactic Winds in Multi-phase Models. I. Methodology and Application
topic Astrophysics of Galaxies
url https://arxiv.org/abs/2605.01105