Linear gas mass density: a unifying descriptor of Cosmic Filaments
Abstract
Cosmic filaments connect the nodes of the large-scale web and are thought to harbour a substantial fraction of the low-z baryon budget, yet a physically motivated framework for organising their diverse gas properties has been lacking. Here we show that the linear mass density Λ = M_gas/L_fil, measured within the entropy radius r_K (the peak of the radial gas entropy profile) plays this role, analogous to mass in halo physics. Using TNG300-1 at z=0, we characterise the structural, thermodynamic, and chemical properties of 5637 filaments spanning more than two decades in Λ. Filaments form a continuous thermodynamic sequence with Λ, ranging from long, thin, cool, metal-poor structures to shorter, wider, hotter, and more enriched ones, with core temperatures spanning two orders of magnitude across the full WHIM window. The ratio of mass- to volume-weighted temperature reveals a shift in heat distribution: low-Λ filaments have their hotter gas preferentially associated with denser material, whereas in high-Λ filaments the hotter gas is diffuse. Well-defined scaling relations connect Λ to temperature, electron density, pressure, entropy, and metallicity, with the T-Λ scaling qualitatively consistent with gravitational heating. We present the first measurement of the gaseous linear mass density function, revealing a broad distribution with a flat low-Λ regime and a steep exponential decline at high Λ, analogous to the halo mass function. The integrated Compton-y parameter Yint scales systematically with Λ, providing a tSZ proxy accessible to current surveys. Finally, galaxy richness per unit length correlates tightly with Λ (Pearson r=0.80), enabling Λ-based classification of filaments from spectroscopic surveys alone and guiding targeted searches for the missing baryons in the cosmic web.
Related
- The Effects of Cosmic Ray Protons on Galactic Nonthermal Filaments
- Self-confinement of ultra-high-energy nuclei in cosmic filaments: implications for the UHECR spectrum and composition
- MIGHTEE-H i : environmental effects of cosmic filaments on extragalactic H i detections in the COSMOS and XMM-LSS fields
- Influence of the large-scale structure velocity field on halo mass assembly within cosmic filaments
- Multi-Band Constraints on Cosmic Strings: Unifying Harmonic and Burst Spectra
BibTeX
@misc{galarragaespinosa2026linear,
title = {{Linear gas mass density: a unifying descriptor of Cosmic Filaments}},
author = {Daniela Galárraga-Espinosa and Daisuke Nagai and Isabel Medlock and Mathieu Langer and Nabila Aghanim and Kentaro Nagamine},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.26306},
eprint = {2610.26306},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.26306},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Linear gas mass density: a unifying descriptor of Cosmic Filaments
AU - Daniela Galárraga-Espinosa
AU - Daisuke Nagai
AU - Isabel Medlock
AU - Mathieu Langer
AU - Nabila Aghanim
AU - Kentaro Nagamine
PY - 2026
DA - 2026/10/19
PB - arXiv
DO - 10.48550/arxiv.2610.26306
UR - https://arxiv.org/abs/2610.26306
AB - Cosmic filaments connect the nodes of the large-scale web and are thought to harbour a substantial fraction of the low-z baryon budget, yet a physically motivated framework for organising their diverse gas properties has been lacking. Here we show that the linear mass density Λ = M_gas/L_fil, measured within the entropy radius r_K (the peak of the radial gas entropy profile) plays this role, analogous to mass in halo physics. Using TNG300-1 at z=0, we characterise the structural, thermodynamic, and chemical properties of 5637 filaments spanning more than two decades in Λ. Filaments form a continuous thermodynamic sequence with Λ, ranging from long, thin, cool, metal-poor structures to shorter, wider, hotter, and more enriched ones, with core temperatures spanning two orders of magnitude across the full WHIM window. The ratio of mass- to volume-weighted temperature reveals a shift in heat distribution: low-Λ filaments have their hotter gas preferentially associated with denser material, whereas in high-Λ filaments the hotter gas is diffuse. Well-defined scaling relations connect Λ to temperature, electron density, pressure, entropy, and metallicity, with the T-Λ scaling qualitatively consistent with gravitational heating. We present the first measurement of the gaseous linear mass density function, revealing a broad distribution with a flat low-Λ regime and a steep exponential decline at high Λ, analogous to the halo mass function. The integrated Compton-y parameter Y^int scales systematically with Λ, providing a tSZ proxy accessible to current surveys. Finally, galaxy richness per unit length correlates tightly with Λ (Pearson r=0.80), enabling Λ-based classification of filaments from spectroscopic surveys alone and guiding targeted searches for the missing baryons in the cosmic web.
ER -