Mass Proxy Quality of Massive Halo Properties in the IllustrisTNG and FLAMINGO Simulations: I. Hot Gas. Aljamal, E., Evrard, A. E, Farahi, A., Pillepich, A., Nelson, D., Schaye, J., Schaller, M., & Braspenning, J. Monthly Notices of the Royal Astronomical Society, 544(1):67–94, Oxford University Press on behalf of Royal Astronomical Society, October, 2025. ![Mass Proxy Quality of Massive Halo Properties in the IllustrisTNG and FLAMINGO Simulations: I. Hot Gas [link]](https://bibbase.org/img/filetypes/link.svg "link")
Paper abstract bibtex We examine scale and redshift dependence of mass-property relations (MPRs) for five hot gas properties of two large groupand cluster-scale halo samples realized by the IllustrisTNG, TNG-Cluster and FLAMINGO cosmological hydrodynamical simulations. For intrinsic properties of i) hot gas mass (𝑀gas), ii) spectroscopic-like temperature (𝑇sl), iii) soft-band X-ray luminosity (𝐿X), and iv) X-ray (𝑌X) and v) Sunyaev-Zel’dovich (𝑌SZ) thermal energies, we use MPR parameters to infer mass proxy quality (MPQ) — the implied scatter in total halo mass conditioned on a property — for halos with 𝑀500c ≥ 1013 M⊙ at redshifts, 𝑧 ∈ \0, 0.5, 1, 2\. We find: (1) in general, scaling relation slopes and covariance display moderate to strong dependence on halo mass, with redshift dependence secondary; (2) for halos with 𝑀500c \textgreater 1014 M⊙, scalings of 𝑀gas and 𝑌SZ simplify toward self-similar slope and constant intrinsic scatter (5 and 10%, respectively) nearly independent of scale, making both measures ideal for cluster finding and characterization to 𝑧 = 2; (3) halo mass-conditioned likelihoods of hot gas mass and thermal energy closely follow a log-normal form; (4) despite normalization differences up to 0.4 dex between the two simulations, higher-order scaling features such as slopes and property covariance show much better agreement. Slopes show appreciable redshift dependence at the group scale, while redshift dependence of the scatter is exhibited by low mass FLAMINGO halos only; (5) property correlations are largely consistent between the simulations, with values that mainly agree with existing empirical measurements. We close with a literature survey placing our MPR slopes and intrinsic scatter estimates into community context.
@article{aljamal_mass_2025,
title = {Mass {Proxy} {Quality} of {Massive} {Halo} {Properties} in the {IllustrisTNG} and {FLAMINGO} {Simulations}: {I}. {Hot} {Gas}},
volume = {544},
url = {https://doi.org/10.1093/mnras/staf1665},
abstract = {We examine scale and redshift dependence of mass-property relations (MPRs) for five hot gas properties of two large groupand cluster-scale halo samples realized by the IllustrisTNG, TNG-Cluster and FLAMINGO cosmological hydrodynamical simulations. For intrinsic properties of i) hot gas mass (𝑀gas), ii) spectroscopic-like temperature (𝑇sl), iii) soft-band X-ray luminosity (𝐿X), and iv) X-ray (𝑌X) and v) Sunyaev-Zel’dovich (𝑌SZ) thermal energies, we use MPR parameters to infer mass proxy quality (MPQ) — the implied scatter in total halo mass conditioned on a property — for halos with 𝑀500c ≥ 1013 M⊙ at redshifts, 𝑧 ∈ \{0, 0.5, 1, 2\}. We find: (1) in general, scaling relation slopes and covariance display moderate to strong dependence on halo mass, with redshift dependence secondary; (2) for halos with 𝑀500c {\textgreater} 1014 M⊙, scalings of 𝑀gas and 𝑌SZ simplify toward self-similar slope and constant intrinsic scatter (5 and 10\%, respectively) nearly independent of scale, making both measures ideal for cluster finding and characterization to 𝑧 = 2; (3) halo mass-conditioned likelihoods of hot gas mass and thermal energy closely follow a log-normal form; (4) despite normalization differences up to 0.4 dex between the two simulations, higher-order scaling features such as slopes and property covariance show much better agreement. Slopes show appreciable redshift dependence at the group scale, while redshift dependence of the scatter is exhibited by low mass FLAMINGO halos only; (5) property correlations are largely consistent between the simulations, with values that mainly agree with existing empirical measurements. We close with a literature survey placing our MPR slopes and intrinsic scatter estimates into community context.},
language = {en},
number = {1},
journal = {Monthly Notices of the Royal Astronomical Society},
publisher = {Oxford University Press on behalf of Royal Astronomical Society},
author = {Aljamal, Eddie and Evrard, August E and Farahi, Arya and Pillepich, Annalisa and Nelson, Dylan and Schaye, Joop and Schaller, Matthieu and Braspenning, Joey},
month = oct,
year = {2025},
keywords = {Explainable},
pages = {67--94},
}
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For intrinsic properties of i) hot gas mass (𝑀gas), ii) spectroscopic-like temperature (𝑇sl), iii) soft-band X-ray luminosity (𝐿X), and iv) X-ray (𝑌X) and v) Sunyaev-Zel’dovich (𝑌SZ) thermal energies, we use MPR parameters to infer mass proxy quality (MPQ) — the implied scatter in total halo mass conditioned on a property — for halos with 𝑀500c ≥ 1013 M⊙ at redshifts, 𝑧 ∈ \\0, 0.5, 1, 2\\. We find: (1) in general, scaling relation slopes and covariance display moderate to strong dependence on halo mass, with redshift dependence secondary; (2) for halos with 𝑀500c \\textgreater 1014 M⊙, scalings of 𝑀gas and 𝑌SZ simplify toward self-similar slope and constant intrinsic scatter (5 and 10%, respectively) nearly independent of scale, making both measures ideal for cluster finding and characterization to 𝑧 = 2; (3) halo mass-conditioned likelihoods of hot gas mass and thermal energy closely follow a log-normal form; (4) despite normalization differences up to 0.4 dex between the two simulations, higher-order scaling features such as slopes and property covariance show much better agreement. Slopes show appreciable redshift dependence at the group scale, while redshift dependence of the scatter is exhibited by low mass FLAMINGO halos only; (5) property correlations are largely consistent between the simulations, with values that mainly agree with existing empirical measurements. 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For intrinsic properties of i) hot gas mass (𝑀gas), ii) spectroscopic-like temperature (𝑇sl), iii) soft-band X-ray luminosity (𝐿X), and iv) X-ray (𝑌X) and v) Sunyaev-Zel’dovich (𝑌SZ) thermal energies, we use MPR parameters to infer mass proxy quality (MPQ) — the implied scatter in total halo mass conditioned on a property — for halos with 𝑀500c ≥ 1013 M⊙ at redshifts, 𝑧 ∈ \\{0, 0.5, 1, 2\\}. We find: (1) in general, scaling relation slopes and covariance display moderate to strong dependence on halo mass, with redshift dependence secondary; (2) for halos with 𝑀500c {\\textgreater} 1014 M⊙, scalings of 𝑀gas and 𝑌SZ simplify toward self-similar slope and constant intrinsic scatter (5 and 10\\%, respectively) nearly independent of scale, making both measures ideal for cluster finding and characterization to 𝑧 = 2; (3) halo mass-conditioned likelihoods of hot gas mass and thermal energy closely follow a log-normal form; (4) despite normalization differences up to 0.4 dex between the two simulations, higher-order scaling features such as slopes and property covariance show much better agreement. 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