The youth of the intracluster medium. I. A non-parametric characterisation of the gas and electron number density profiles of z ≃ 2 protoclusters
Abstract
Context. Protoclusters of galaxies are the earliest phase in the assembly of galaxy clusters and can provide invaluable information about plasma physics, cosmic magnetism, and cosmology. However, due to small angular sizes and cosmological dimming, observing the proto-intracluster medium (proto-ICM) associated with protocluster cores is far from trivial. Aims. We aim to provide a non-parametric description of the gas mass and electron number density profiles of the proto-ICM at z = 2, and to study their dependence on mass, dynamical state and central activity. Methods. We extract and analyse over $3800$ regions around protocluster cores with spherical-overdensity masses above M500c > 1013 M⊙ out of a large simulated volume within the Magneticum suite. We study their density profiles, temperature structure, ionisation degree and electron number density as a function of mass and other secondary properties characterising dynamical state and central activity, extending from the central halo to the surrounding protocluster environment. Results. Protoclusters present moderate deviations from self-similarity in their density profiles and temperature structure, with a strong double-β structure especially relevant at high masses and intense AGN accretion. Hot, ionised gas is only dominant at intermediate radii (r ≳ [0.1−0.5] R500c), where its density also correlates with mass and dynamical disturbance. Conclusions. These results constitute the basis for a forthcoming parametric calibration of proto-ICM density profiles, which could be useful for interpreting observables sensitive to the density and ionisation of the diffuse gas.
Versions
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BibTeX
@article{vallesperez2026youth,
title = {{The youth of the intracluster medium. I. A non-parametric characterisation of the gas and electron number density profiles of $z \simeq 2$ protoclusters}},
author = {David Vallés-Pérez and Annalisa Bonafede and Klaus Dolag and Marco Balboni and Paolo Tozzi and Marika Lepore},
journal = {Astron.Astrophys.},
year = {2026},
month = sep,
doi = {10.1051/0004-6361/202660465},
eprint = {2607.02654},
archivePrefix = {arXiv},
url = {https://hal.science/hal-05734254v1},
}
RIS
TY - JOUR
TI - The youth of the intracluster medium. I. A non-parametric characterisation of the gas and electron number density profiles of z ≃ 2 protoclusters
AU - David Vallés-Pérez
AU - Annalisa Bonafede
AU - Klaus Dolag
AU - Marco Balboni
AU - Paolo Tozzi
AU - Marika Lepore
PY - 2026
DA - 2026/09/01
JO - Astron.Astrophys.
DO - 10.1051/0004-6361/202660465
UR - https://hal.science/hal-05734254v1
AB - Context. Protoclusters of galaxies are the earliest phase in the assembly of galaxy clusters and can provide invaluable information about plasma physics, cosmic magnetism, and cosmology. However, due to small angular sizes and cosmological dimming, observing the proto-intracluster medium (proto-ICM) associated with protocluster cores is far from trivial. Aims. We aim to provide a non-parametric description of the gas mass and electron number density profiles of the proto-ICM at z = 2, and to study their dependence on mass, dynamical state and central activity. Methods. We extract and analyse over $3800$ regions around protocluster cores with spherical-overdensity masses above M_500c > 10^13 M_⊙ out of a large simulated volume within the Magneticum suite. We study their density profiles, temperature structure, ionisation degree and electron number density as a function of mass and other secondary properties characterising dynamical state and central activity, extending from the central halo to the surrounding protocluster environment. Results. Protoclusters present moderate deviations from self-similarity in their density profiles and temperature structure, with a strong double-β structure especially relevant at high masses and intense AGN accretion. Hot, ionised gas is only dominant at intermediate radii (r ≳ [0.1−0.5] R_500c), where its density also correlates with mass and dynamical disturbance. Conclusions. These results constitute the basis for a forthcoming parametric calibration of proto-ICM density profiles, which could be useful for interpreting observables sensitive to the density and ionisation of the diffuse gas.
ER -