2002/10/23 by Yan-Jie Xue, Yan‐Jie Xue, Xiangping Wu +1 · 1 citation
Physics and Astronomy · #Active galactic nucleus #Amplitude #Astrophysics #COSMIC cancer database #Cosmic ray #Cosmology and Gravitation Theories #Dark Matter and Cosmic Phenomena #Dark matter #Galaxies: Formation, Evolution, Phenomena #Galaxy #Metallicity #Physics #Radiative cooling #Radiative transfer #X-ray background #astro-ph
paper · pdf · doi:10.1086/345539
published as Astrophys.J. 584 (2003) 34-44 · 14 pages, 6 figures, accepted for publication in ApJ
arxiv created 2002/10/23 · openalex publication_date 2003/02/10 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Using a simple analytic approach we address the question of whether radiative cooling, nongravitational heating, and cooling plus heating models can simultaneously explain the observed global X-ray properties (entropy and X-ray luminosity distributions) of groups and clusters and the residual soft X-ray background (XRB) after discrete sources are removed. Within the framework of typical cold dark matter structure formation characterized by an amplitude of matter power spectrum σ 8 = 0.9, it is argued that while radiative cooling alone is able to marginally reproduce the entropy floor detected in the central regions of groups and clusters, it is insufficient to account for the steepening of the X-ray luminosity-temperature relation for groups and the unresolved soft XRB. A phenomenological preheating model, in which either an extra specific energy budget or an entropy floor is added to the hot gas in groups and clusters, fails in the recovery of at least one of the X-ray observed features. Finally, the soft XRB predicted by our combined model of cooling plus heating exceeds the observational upper limits by a factor of ~2, if the model is required to reproduce the observed entropy and X-ray luminosity-temperature relationships of groups and clusters. Inclusion of the cosmic variation of metallicity and the self-absorption of the cooled gas as a result of radiative cooling in groups and clusters, or exclusion of the contribution of nearby massive clusters to the XRB, does not significantly alter the situation. If the discrepancy is not a result of the oversimplification of our analytic models, this implies that either our current understanding of the physical processes of the hot gas is still incomplete, or the normalization of the present power spectrum has been systematically overestimated. For the latter, both the X-ray properties of groups and clusters and the XRB predicted by the preheating model and the cooling plus heating model can be reconciled with the X-ray observations if a lower value of the normalization parameter σ 8 ≈ 0.7 is assumed.