Introducing the Descriptive Parametric Model: Gaseous Profiles for Galaxies, Groups, and Clusters

TL;DR

The paper introduces the Descriptive Parametric Model (DPM) for generating radially dependent gas properties in halos from galaxies to clusters, incorporating mass and redshift scaling via a generalized NFW framework with 32 parameters. It shows how to produce mock observables across X-ray, SZ, FRB DMs, and UV absorption, enabling cross-band comparisons to assess baryon content, pressure, and density structure. Through three initial model variants that differ in self-similarity, gas fraction, and slope evolution, the study demonstrates both alignments and tensions with multi-wavelength data, finding that models with reduced baryon content and mass dependent slope changes often perform best but cannot simultaneously fit all observables. The DPMhalo code and a growing data library are released to support future cross-band analyses and large survey modeling, highlighting the potential to refine our understanding of CGM and ICM gas distributions and the role of non-thermal processes. The work emphasizes biases and systematics in interpreting observables, and points to the need for more stringent multi-band constraints to fully characterize gaseous halos.

Abstract

We develop and present the Descriptive Parametric Model (DPM), a tool for generating profiles of gaseous halos (pressure, electron density, and metallicity) as functions of radius, halo mass, and redshift. The model assumes single-phase, spherically symmetric, volume-filling warm/hot gas. The DPM framework enables mock observations of the circumgalactic medium (CGM), group halos, and clusters across a number of wavebands including X-ray, sub-millimeter/millimeter, radio, and ultraviolet (UV). We introduce three model families calibrated to reproduce cluster profiles while having different extrapolations to the CGM -- (i) self-similar halos, (ii) a reduced gas model for lower halo masses, and (iii) a model with shallower radial slopes at lower masses. We demonstrate how our z=0.0-0.6 models perform when applied to stacked and individual X-ray emission profiles, measurements of the thermal and kinetic Sunyaev-Zel'dovich Effect, electron dispersion measures from fast radio bursts, O VI absorption, and UV-derived pressures. Our investigation supports models that remove baryons from halos more effectively and have shallower profiles at lower halo mass. We discuss biases and systematics when modelling observables using consistent hot gaseous halo models for all wavebands explored. We release the DPMhalo code to encourage the use of our framework and new formulations in future investigations. Included with the DPMhalo distribution is a set of recent observations that allow the reproduction of most plots in this paper.

Figures (18)

• Figure 1: Left: Normalized pressure for the three models at three masses ($L^\star$- blue, Groups- light green, and Clusters- dark red). Clusters for all models and all profiles from Model 1 overlap the dark red DPM profile. Right: Mass dependence for Model 3. The color scheme for halo masses, indicated by the colorbar, is used throughout all figures for DPMs and observational datasets. The masses shown on the right are log($M_{200}/{\rm M}_{\odot}$)=11.5, 12.0, 12.5, 13.0, 13.5, 14.0, 14.5, & 15.0. The Arnaud2010 pressure relationships derived from clusters are shown for 3 masses. The sun2011 median profile for massive groups and the G19 fitted profile from X-COP clusters are also indicated (the latter is mostly overlapped by the $10^{15.0}\;{\rm M}_{\odot}$ DPM profiles). These datasets are more clearly shown in the unnormalized pressure plot in Fig. \ref{['fig:pressure_all']}. Dotted vertical lines indicating $R_{200}$ and $R_{500}$ are repeated for all physical property figures.
• Figure 2: Left: Electron density for the three models at three masses as in Fig. \ref{['fig:pressure_norm']}. Right: Mass dependence for Model 3, analogous to Fig. \ref{['fig:pressure_norm']}. The sun2009 and lovisari2015 groups median profiles, the McDonald2017 fit to clusters, and the Ghirardini2019 fit to X-COP clusters are plotted in both panels, with the latter underlying the cluster DPM profiles.
• Figure 3: Metallicity profiles as a function of radius. All DPM $Z$ profiles are invariant between models, mass bins, and redshifts; hence they overlap. These profiles are calibrated to the lovisari2019 groups dataset.
• Figure 4: Gas fraction as a function of $M_{200}$ inside $R_{200}$ (filled symbols) and inside $R_{500}$ (open symbols). The dashed horizontal line indicates the cosmic baryon fraction $f_{\rm b}$. The relationship of Akino2022 inside $R_{500}$ and the corresponding $1\;\sigma$ range are indicated by black dashed lines. This relationship should be compared to the open model symbols. Models 2 and 3 are calibrated to reproduce the Akino2022 gas fractions.
• Figure 5: Normalized entropy at as a function of radius for the span of halo masses across the three models. The Voit2005 baseline entropy profile is plotted as well. The entropy profiles for Model 1 overlap.