Hot atmospheres of galaxies, groups, and clusters of galaxies (2001.10023v1)

Abstract: Most of the ordinary matter in the local Universe has not been converted into stars but resides in a largely unexplored diffuse, hot, X-ray emitting plasma. It pervades the gravitational potentials of massive galaxies, groups and clusters of galaxies, as well as the filaments of the cosmic web. The physics of this hot medium, such as its dynamics, thermodynamics and chemical composition can be studied using X-ray spectroscopy in great detail. Here, we present an overview of the basic properties and discuss the self similarity of the hot "atmospheres" permeating the gravitational halos from the scale of galaxies, through groups, to massive clusters. Hot atmospheres are stabilised by the activity of supermassive black holes and, in many ways, they are of key importance for the evolution of their host galaxies. The hot plasma has been significantly enriched in heavy elements by supernovae during the period of maximum star formation activity, probably more than 10 billion years ago. High resolution X-ray spectroscopy just started to be able to probe the dynamics of atmospheric gas and future space observatories will determine the properties of the currently unseen hot diffuse medium throughout the cosmic web.

• The paper demonstrates self-similarity in scaling relations, linking gas temperature and mass across galaxies, groups, and clusters using X-ray spectroscopy.
• It reveals that supermassive black hole feedback stabilizes hot atmospheres, effectively preventing rapid cooling in these high-temperature environments.
• The study uncovers universal chemical enrichment, with supernovae dispersing heavy elements that inform the metal distribution in cosmic structures.

An Overview of Hot Atmospheres in Galaxies, Groups, and Galaxy Clusters

The paper "Hot Atmospheres of Galaxies, Groups, and Clusters of Galaxies" by Norbert Werner and François Mernier provides an in-depth analysis of the diffuse hot X-ray emitting plasma that dominates the baryonic matter in the universe. The paper focuses on understanding the properties, dynamics, and implications of these hot atmospheres, which pervade the gravitational potentials of massive galaxies and extend through groups and clusters of galaxies.

Summary of Key Findings

Most baryonic matter in the local universe resides in a hot, diffuse phase, forming extensive halos around galaxies, groups, and clusters, and further extending into the cosmic web's filaments. These hot atmospheres, characterized by their high temperatures and rich ionization states, can be effectively studied using X-ray spectroscopy, providing key insights into their physics and impact on cosmic structure.

• Self-Similarity and Scaling Relations: The research emphasizes the concept of self-similarity across different scales—from galaxies to massive clusters. For a given overdensity, the total mass and gas temperature scale predictably, allowing us to test theories of structure formation.
• Dynamics and Stability: Supermassive black holes play a critical role in stabilizing these atmospheres. The paper highlights how the interplay between gravitational forces and black hole-triggered feedback mechanisms satisfies cooling timescales, preventing an unchecked collapse of gaseous atmospheres into star-forming regions.
• Chemical Enrichment: The hot plasma is rich in heavy elements, significantly enriched by supernovae billions of years ago. Such an enrichment reflects a universal metal distribution consistent with solar proportions, implicating both Type Ia and core-collapse supernovae as sources of metal dispersion.
• Observational Techniques: High-resolution X-ray spectroscopy enables observations of the gas dynamical states and chemical compositions across vast distances. While space-based X-ray observatories like Chandra and XMM-Newton have significantly advanced our understanding, limitations at large radii remain, necessitating future missions.
• Future Prospects: The paper advocates for the development of more sensitive instruments to probe the largely unseen diffuse medium throughout the cosmic web. The authors speculate that upcoming space observatories will enhance our understanding of the missing baryon problem and refine estimates of the baryonic mass fraction within various halo structures.

Implications

The implications of this research touch upon key areas in astrophysics, presenting a narrative where the dynamics and thermodynamics of hot gas in galaxies and clusters are pivotal for the evolution of large-scale cosmic structures. The stabilization and enrichment of these atmospheres provide critical feedback mechanisms shaping both individual galaxies and larger cosmic webs.

Practically, this research informs the design of future X-ray observatories, emphasizing the importance of improved spatial, spectral, and temporal resolution to capture the intricate details of gas dynamics and composition at both local and cosmological scales.

Conclusion

Continued exploration of hot atmospheres remains a frontier in astrophysical research, bridging gaps in understanding the integration of baryonic matter into the cosmic scaffolding. As technology advances, our ability to probe these structures more thoroughly will yield significant insights into the physical processes governing the universe's evolution. Moreover, unraveling the physics of these complex structures offers a direct connection to the fundamental processes of galaxy formation and evolution, enriching our comprehension of the universe.