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research article

On the distribution of the cold neutral medium in galaxy discs

Smith, Rowan J.
•
Tress, Robin  
•
Soler, Juan D.
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July 4, 2023
Monthly Notices Of The Royal Astronomical Society

The cold neutral medium (CNM) is an important part of the galactic gas cycle and a precondition for the formation of molecular and star-forming gas, yet its distribution is still not fully understood. In this work, we present extremely high resolution simulations of spiral galaxies with time-dependent chemistry such that we can track the formation of the CNM, its distribution within the galaxy, and its correlation with star formation. We find no strong radial dependence between the CNM fraction and total neutral atomic hydrogen (H i) due to the decreasing interstellar radiation field counterbalancing the decreasing gas column density at larger galactic radii. However, the CNM fraction does increase in spiral arms where the CNM distribution is clumpy, rather than continuous, overlapping more closely with H-2. The CNM does not extend out radially as far as H i, and the vertical scale height is smaller in the outer galaxy compared to H i with no flaring. The CNM column density scales with total mid-plane pressure and disappears from the gas phase below values of P-T/k(B) = 1000 K cm(-3). We find that the star formation rate density follows a similar scaling law with CNM column density to the total gas Kennicutt-Schmidt law. In the outer galaxy, we produce realistic vertical velocity dispersions in the H i purely from galactic dynamics, but our models do not predict CNM at the extremely large radii observed in H i absorption studies of the Milky Way. We suggest that extended spiral arms might produce isolated clumps of CNM at these radii.

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Type
research article
DOI
10.1093/mnras/stad1537
Web of Science ID

WOS:001025658500004

Author(s)
Smith, Rowan J.
Tress, Robin  
Soler, Juan D.
Klessen, Ralf S.
Glover, Simon C. O.
Hennebelle, Patrick
Molinari, Sergio
Low, Mordecai-Mark Mac
Whitworth, David
Date Issued

2023-07-04

Publisher

OXFORD UNIV PRESS

Published in
Monthly Notices Of The Royal Astronomical Society
Volume

524

Issue

1

Start page

873

End page

885

Subjects

Astronomy & Astrophysics

•

methods: numerical

•

ism: kinematics and dynamics

•

ism: structure

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supernova-driven ism

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forming molecular gas

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star-formation laws

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interstellar-medium

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milky-way

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h-i

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spiral galaxy

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filamentary structure

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atomic-hydrogen

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line survey

Editorial or Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
LASTRO  
Available on Infoscience
August 14, 2023
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/199853
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