Special Issue "The Physical Properties of the Groups of Galaxies"

A special issue of Universe (ISSN 2218-1997). This special issue belongs to the section "Galaxies and Clusters".

Deadline for manuscript submissions: closed (31 March 2021).

Special Issue Editors

Dr. Lorenzo Lovisari
E-Mail Website
Guest Editor
INAF, Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, via Pietro Gobetti 93/3, 40129 Bologna, Italy
Interests: groups and clusters of galaxies; intracluster medium; X-ray; cosmology
Dr. Stefano Ettori
E-Mail Website
Guest Editor
INAF, Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, via Pietro Gobetti 93/3, 40129 Bologna, Italy
Interests: galaxy clusters; intracluster medium; X-ray; dark matter; cosmology

Special Issue Information

Dear Colleagues,

Galaxy groups consist of a few tens of galaxies bound in a common gravitational potential and contain a significant fraction of the overall universal baryon budget. Therefore, they are key to our understanding of how the bulk of matter in the Universe accretes and forms hierarchical structures and how different sources of feedback affect their gravitational collapse. However, despite their crucial role in cosmic structure formation and evolution, galaxy groups have received less attention compared to massive clusters. This is perhaps in part due to their rarity in being observed and properly characterized. With the advent of eROSITA, many thousands of galaxy groups will be detected by X-ray, complementing optical and SZ coverage.

It is time to collect and organize the latest developments in our understanding of these systems and present future prospects from both observational and theoretical points of view.

This Special Issue aims to foster progress in the field of the physical properties of galaxy groups, facilitating effective cross-communication between observers, theorists, and simulators. Topics of interest to this Special Issue include (but are most certainly not limited to) multi-wavelength observations of single objects and samples, hydrodynamical simulations of cosmic structures, fossil/compact groups, the physics of the intragroup plasma and the distribution of the metals, and the scaling relations and their impact on cosmology.


Dr. Lorenzo Lovisari
Dr. Stefano Ettori
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Universe is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • observations
  • numerical simulations
  • cosmology
  • plasmas
  • galaxies

Published Papers (3 papers)

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Review

Open AccessReview
Feedback from Active Galactic Nuclei in Galaxy Groups
Universe 2021, 7(5), 142; https://doi.org/10.3390/universe7050142 - 11 May 2021
Viewed by 97
Abstract
The co-evolution between supermassive black holes and their environment is most directly traced by the hot atmospheres of dark matter halos. The cooling of the hot atmosphere supplies the central regions with fresh gas, igniting active galactic nuclei (AGN) with long duty cycles. [...] Read more.
The co-evolution between supermassive black holes and their environment is most directly traced by the hot atmospheres of dark matter halos. The cooling of the hot atmosphere supplies the central regions with fresh gas, igniting active galactic nuclei (AGN) with long duty cycles. Outflows from the central engine tightly couple with the surrounding gaseous medium and provide the dominant heating source preventing runaway cooling by carving cavities and driving shocks across the medium. The AGN feedback loop is a key feature of all modern galaxy evolution models. Here, we review our knowledge of the AGN feedback process in the specific context of galaxy groups. Galaxy groups are uniquely suited to constrain the mechanisms governing the cooling–heating balance. Unlike in more massive halos, the energy that is supplied by the central AGN to the hot intragroup medium can exceed the gravitational binding energy of halo gas particles. We report on the state-of-the-art in observations of the feedback phenomenon and in theoretical models of the heating-cooling balance in galaxy groups. We also describe how our knowledge of the AGN feedback process impacts galaxy evolution models and large-scale baryon distributions. Finally, we discuss how new instrumentation will answer key open questions on the topic. Full article
(This article belongs to the Special Issue The Physical Properties of the Groups of Galaxies)
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Open AccessReview
Scaling Properties of Galaxy Groups
Universe 2021, 7(5), 139; https://doi.org/10.3390/universe7050139 - 10 May 2021
Viewed by 77
Abstract
Galaxy groups and poor clusters are more common than rich clusters, and host the largest fraction of matter content in the Universe. Hence, their studies are key to understand the gravitational and thermal evolution of the bulk of the cosmic matter. Moreover, because [...] Read more.
Galaxy groups and poor clusters are more common than rich clusters, and host the largest fraction of matter content in the Universe. Hence, their studies are key to understand the gravitational and thermal evolution of the bulk of the cosmic matter. Moreover, because of their shallower gravitational potential, galaxy groups are systems where non-gravitational processes (e.g., cooling, AGN feedback, star formation) are expected to have a higher impact on the distribution of baryons, and on the general physical properties, than in more massive objects, inducing systematic departures from the expected scaling relations. Despite their paramount importance from the astrophysical and cosmological point of view, the challenges in their detection have limited the studies of galaxy groups. Upcoming large surveys will change this picture, reassigning to galaxy groups their central role in studying the structure formation and evolution in the Universe, and in measuring the cosmic baryonic content. Here, we review the recent literature on various scaling relations between X-ray and optical properties of these systems, focusing on the observational measurements, and the progress in our understanding of the deviations from the self-similar expectations on groups’ scales. We discuss some of the sources of these deviations, and how feedback from supernovae and/or AGNs impacts the general properties and the reconstructed scaling laws. Finally, we discuss future prospects in the study of galaxy groups. Full article
(This article belongs to the Special Issue The Physical Properties of the Groups of Galaxies)
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Open AccessReview
Properties of Fossil Groups of Galaxies
Universe 2021, 7(5), 132; https://doi.org/10.3390/universe7050132 - 04 May 2021
Viewed by 188
Abstract
We review the formation and evolution of fossil groups and clusters from both the theoretical and the observational points of view. In the optical band, these systems are dominated by the light of the central galaxy. They were interpreted as old systems that [...] Read more.
We review the formation and evolution of fossil groups and clusters from both the theoretical and the observational points of view. In the optical band, these systems are dominated by the light of the central galaxy. They were interpreted as old systems that had enough time to merge all the M* galaxies within the central one. During the last two decades, many observational studies were performed to prove the old and relaxed state of fossil systems. The majority of these studies that spans a wide range of topics including halos global scaling relations, dynamical substructures, stellar populations, and galaxy luminosity functions seem to challenge this scenario. The general picture that can be obtained by reviewing all the observational works is that the fossil state could be transitional. Indeed, the formation of the large magnitude gap observed in fossil systems could be related to internal processes rather than an old formation. Full article
(This article belongs to the Special Issue The Physical Properties of the Groups of Galaxies)
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