The environmental dependence of the circumgalactic medium in a high-resolution cosmological simulation
Abstract
There is increasing evidence from observations that the circumgalactic medium (CGM) of galaxies depends on the large-scale structure in which they are embedded. When probing the CGM in absorption using quasar sightlines, studies find an enhanced sky coverage in the CGM of galaxies in overdensities compared to galaxies in isolation. However, the exact reason for this environmental dependence is still unclear. In this work we aim to model for the first time the influence of the large-scale structure on the cool and warm (T∼104−5 K) gas phases of the CGM. We use a high-resolution (mgas≈ 4.5× 104 M⊙, mdm≈ 2.4× 105 M⊙) cosmological simulation based on the EAGLE model of galaxy formation. We select all galaxies at z=0 with stellar mass M*>108 M⊙ and split them into galaxies in overdensities (group galaxies) and galaxies in isolation using a Friends-of-Friends algorithm. For these two samples, we investigate how the large-scale structure influences the physical properties of the CGM and the measured covering fractions of the cool and warm gas phases. When the two samples of group and isolated galaxies are matched in stellar mass, halo mass, and we use only central galaxies, we do not find any significant difference in the physical properties of the CGM and the measured covering fractions. However, when satellite galaxies are included, we recover the observational trends in the difference of covering fractions with the environment. The difficulty of recovering the observational trends shows the complexity of capturing the multiphase CGM in simulations. However, since our results concerning the admixture of satellites are independent of the employed subgrid physics, this work shows that central galaxies and satellites need to be disentangled in observational studies to clearly discern the role of the environment on the CGM.
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BibTeX
@misc{herzog2026environmental,
title = {{The environmental dependence of the circumgalactic medium in a high-resolution cosmological simulation}},
author = {Georg Herzog and Rajeshwari Dutta and Michele Fumagalli},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.08654},
eprint = {2609.08654},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.08654},
}
RIS
TY - UNPB
TI - The environmental dependence of the circumgalactic medium in a high-resolution cosmological simulation
AU - Georg Herzog
AU - Rajeshwari Dutta
AU - Michele Fumagalli
PY - 2026
DA - 2026/09/08
PB - arXiv
DO - 10.48550/arxiv.2609.08654
UR - https://arxiv.org/abs/2609.08654
AB - There is increasing evidence from observations that the circumgalactic medium (CGM) of galaxies depends on the large-scale structure in which they are embedded. When probing the CGM in absorption using quasar sightlines, studies find an enhanced sky coverage in the CGM of galaxies in overdensities compared to galaxies in isolation. However, the exact reason for this environmental dependence is still unclear. In this work we aim to model for the first time the influence of the large-scale structure on the cool and warm (T∼10^4−5 K) gas phases of the CGM. We use a high-resolution (m_gas≈ 4.5× 10^4 M_⊙, m_dm≈ 2.4× 10^5 M_⊙) cosmological simulation based on the EAGLE model of galaxy formation. We select all galaxies at z=0 with stellar mass M_*>10^8 M_⊙ and split them into galaxies in overdensities (group galaxies) and galaxies in isolation using a Friends-of-Friends algorithm. For these two samples, we investigate how the large-scale structure influences the physical properties of the CGM and the measured covering fractions of the cool and warm gas phases. When the two samples of group and isolated galaxies are matched in stellar mass, halo mass, and we use only central galaxies, we do not find any significant difference in the physical properties of the CGM and the measured covering fractions. However, when satellite galaxies are included, we recover the observational trends in the difference of covering fractions with the environment. The difficulty of recovering the observational trends shows the complexity of capturing the multiphase CGM in simulations. However, since our results concerning the admixture of satellites are independent of the employed subgrid physics, this work shows that central galaxies and satellites need to be disentangled in observational studies to clearly discern the role of the environment on the CGM.
ER -