Where is the Supervirial Gas? The Supply from Hot Inflows

To understand the presence of the supervirial temperature gas detected in the Milky Way (MW), we present our findings from isolated galaxy simulations of MW-mass systems using GIZMO with the Feedback in Realistic Environments (FIRE-2) stellar feedback model. It unveils the presence of a significant...

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Main Authors: Manami Roy, Kung-Yi Su, Smita Mathur, Jonathan Stern
Format: Article
Language:English
Published: IOP Publishing 2025-01-01
Series:The Astrophysical Journal
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Online Access:https://doi.org/10.3847/1538-4357/ade059
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author Manami Roy
Kung-Yi Su
Smita Mathur
Jonathan Stern
author_facet Manami Roy
Kung-Yi Su
Smita Mathur
Jonathan Stern
author_sort Manami Roy
collection DOAJ
description To understand the presence of the supervirial temperature gas detected in the Milky Way (MW), we present our findings from isolated galaxy simulations of MW-mass systems using GIZMO with the Feedback in Realistic Environments (FIRE-2) stellar feedback model. It unveils the presence of a significant supervirial temperature ( T  >  T _vir ) gas component within 20 kpc from the galactic center. We also find that 70%–90% of the total supervirial gas is extraplanar, at 1 <  z  < 6 kpc and R _cyl  < 15 kpc. This supervirial gas has a mass of 1−2 × 10 ^7 M _⊙ with typical gas densities are 10 ^−3.5 −10 ^−2.5 cm ^−3 . We find that some of the virial gas ( T  ∼ 10 ^6 K) forms a rotating hot inflow, where gravitational energy is converted to thermal energy mainly via compressive heating. This process causes gas falling close to the rotation axis to reach supervirial temperatures via a combination of compressive heating and shocks just before cooling and joining the disk. Stellar feedback heating accounts for less than 1% of the supervirial gas, indicating its minimal influence despite expectations. Even in scenarios with no stellar feedback effects considered, abundant supervirial gas persists, highlighting the dominance of alternative heating mechanisms. We also show that cosmic rays do not have a significant effect on heating the gas to a supervirial temperature. Our study illuminates the intricate dynamics of hot virial and supervirial gas surrounding MW-mass galaxies, emphasizing the prominent role of infall-driven compressive and shock-heating processes in shaping thermal evolution.
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spelling doaj-art-8abdc9d2e9674f97865afb65b833a0952025-08-20T03:27:22ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-0198817110.3847/1538-4357/ade059Where is the Supervirial Gas? The Supply from Hot InflowsManami Roy0https://orcid.org/0000-0001-9567-8807Kung-Yi Su1https://orcid.org/0000-0003-1598-0083Smita Mathur2https://orcid.org/0000-0002-4822-3559Jonathan Stern3https://orcid.org/0000-0002-7541-9565Center for Cosmology and Astro Particle Physics (CCAPP), The Ohio State University , 191 West Woodruff Avenue, Columbus, OH 43210, USA ; roy.516@osu.edu; Department of Astronomy, The Ohio State University , 140 West 18th Avenue, Columbus, OH 43210, USABlack Hole Initiative, Harvard University , 20 Garden Street, Cambridge, MA 02138, USACenter for Cosmology and Astro Particle Physics (CCAPP), The Ohio State University , 191 West Woodruff Avenue, Columbus, OH 43210, USA ; roy.516@osu.edu; Department of Astronomy, The Ohio State University , 140 West 18th Avenue, Columbus, OH 43210, USASchool of Physics & Astronomy, Tel Aviv University , Tel Aviv 69978, IsraelTo understand the presence of the supervirial temperature gas detected in the Milky Way (MW), we present our findings from isolated galaxy simulations of MW-mass systems using GIZMO with the Feedback in Realistic Environments (FIRE-2) stellar feedback model. It unveils the presence of a significant supervirial temperature ( T  >  T _vir ) gas component within 20 kpc from the galactic center. We also find that 70%–90% of the total supervirial gas is extraplanar, at 1 <  z  < 6 kpc and R _cyl  < 15 kpc. This supervirial gas has a mass of 1−2 × 10 ^7 M _⊙ with typical gas densities are 10 ^−3.5 −10 ^−2.5 cm ^−3 . We find that some of the virial gas ( T  ∼ 10 ^6 K) forms a rotating hot inflow, where gravitational energy is converted to thermal energy mainly via compressive heating. This process causes gas falling close to the rotation axis to reach supervirial temperatures via a combination of compressive heating and shocks just before cooling and joining the disk. Stellar feedback heating accounts for less than 1% of the supervirial gas, indicating its minimal influence despite expectations. Even in scenarios with no stellar feedback effects considered, abundant supervirial gas persists, highlighting the dominance of alternative heating mechanisms. We also show that cosmic rays do not have a significant effect on heating the gas to a supervirial temperature. Our study illuminates the intricate dynamics of hot virial and supervirial gas surrounding MW-mass galaxies, emphasizing the prominent role of infall-driven compressive and shock-heating processes in shaping thermal evolution.https://doi.org/10.3847/1538-4357/ade059Circumgalactic mediumGalaxy evolutionMilky Way evolution
spellingShingle Manami Roy
Kung-Yi Su
Smita Mathur
Jonathan Stern
Where is the Supervirial Gas? The Supply from Hot Inflows
The Astrophysical Journal
Circumgalactic medium
Galaxy evolution
Milky Way evolution
title Where is the Supervirial Gas? The Supply from Hot Inflows
title_full Where is the Supervirial Gas? The Supply from Hot Inflows
title_fullStr Where is the Supervirial Gas? The Supply from Hot Inflows
title_full_unstemmed Where is the Supervirial Gas? The Supply from Hot Inflows
title_short Where is the Supervirial Gas? The Supply from Hot Inflows
title_sort where is the supervirial gas the supply from hot inflows
topic Circumgalactic medium
Galaxy evolution
Milky Way evolution
url https://doi.org/10.3847/1538-4357/ade059
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