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PreprintCC BY 4.0arXiv

eROSITA cosmology with galaxy groups: Hot gas budget out to the virial radius

  • H. Khalil
  • A. Finoguenov
  • D. Eckert
  • R. Seppi
  • E. Tempel
  • L. Lovisari
  • F. Gastaldello
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Abstract

Non-gravitational processes that expel hot gas beyond the virial regions of groups and clusters of galaxies, known collectively as baryonic feedback, play a key role in reshaping the matter distribution of the Universe on Mpc scales. We use eROSITA observations of a complete sample of 25 galaxy groups selected from the first public release of the eROSITA-DE data (eRASS1) and identified with the Two Micron Redshift Survey optical group catalogue (2MRS). We extract and fit surface brightness (SBx) profiles and present hot gas mass and hot gas fraction profiles out to R200. We perform a Bayesian analysis of Mgas−Mtot, LX−Mtot, and LX−Mgas relations, taking into account the aperture covariance effects. At R500, we report uniformly flat SBx profiles with a mean β parameter of 0.38 ±0.04, steepening to β= 0.76±0.19 beyond R500. We measure a sub-cosmic hot gas fraction at the median mass of our sample M500 = 2.54×1013M⊙ of $ f_{\mathrm{gas,500}} = 4.32\pm0.42\%$. Similarly, at R200 and the median mass M 200 = 3.69×1013M⊙, we obtain fgas,200=5.78±0.69%. Our fgas−Mtot and LX−Mtot relations show significant deviations from the predictions of the strong feedback variants of the FLAMINGO simulation (2.5σ to 8.0σ tension), while fiducial FLAMINGO and BAHAMAS provide the closest match to our measurements. Using our measured baryon fractions and the SP(k) model, we infer a 10%−15% reduction in the matter power spectrum at k = 5 h Mpc−1 relative to a dark matter-only universe, in agreement with fiducial FLAMINGO and BAHAMAS, while revealing a growing tension on smaller scales with the strong feedback variants.

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Cite

BibTeXRIS
BibTeX
@misc{khalil2026erosita,
  title = {{eROSITA cosmology with galaxy groups: Hot gas budget out to the virial radius}},
  author = {H. Khalil and A. Finoguenov and D. Eckert and R. Seppi and E. Tempel and L. Lovisari and F. Gastaldello},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2608.17735},
  eprint = {2608.17735},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2608.17735},
  note = {CC BY 4.0},
}
RIS
TY  - UNPB
TI  - eROSITA cosmology with galaxy groups: Hot gas budget out to the virial radius
AU  - H. Khalil
AU  - A. Finoguenov
AU  - D. Eckert
AU  - R. Seppi
AU  - E. Tempel
AU  - L. Lovisari
AU  - F. Gastaldello
PY  - 2026
DA  - 2026/09/09
PB  - arXiv
DO  - 10.48550/arxiv.2608.17735
UR  - https://arxiv.org/abs/2608.17735
AB  - Non-gravitational processes that expel hot gas beyond the virial regions of groups and clusters of galaxies, known collectively as baryonic feedback, play a key role in reshaping the matter distribution of the Universe on Mpc scales. We use eROSITA observations of a complete sample of 25 galaxy groups selected from the first public release of the eROSITA-DE data (eRASS1) and identified with the Two Micron Redshift Survey optical group catalogue (2MRS). We extract and fit surface brightness (SBx) profiles and present hot gas mass and hot gas fraction profiles out to R_200. We perform a Bayesian analysis of M_gas−M_tot, L_X−M_tot, and L_X−M_gas relations, taking into account the aperture covariance effects. At R_500, we report uniformly flat SBx profiles with a mean β parameter of 0.38 ±0.04, steepening to β= 0.76±0.19 beyond R_500. We measure a sub-cosmic hot gas fraction at the median mass of our sample M_500 = 2.54×10^13M_⊙ of $ f_{\mathrm{gas,500}} = 4.32\pm0.42\%$. Similarly, at R_200 and the median mass M_ 200 = 3.69×10^13M_⊙, we obtain f_gas,200=5.78±0.69%. Our f_gas−M_tot and L_X−M_tot relations show significant deviations from the predictions of the strong feedback variants of the FLAMINGO simulation (2.5σ to 8.0σ tension), while fiducial FLAMINGO and BAHAMAS provide the closest match to our measurements. Using our measured baryon fractions and the SP(k) model, we infer a 10%−15% reduction in the matter power spectrum at k = 5 h Mpc^−1 relative to a dark matter-only universe, in agreement with fiducial FLAMINGO and BAHAMAS, while revealing a growing tension on smaller scales with the strong feedback variants.
ER  -