Properties of Fossil Groups of Galaxies

Aguerri, J. A. L.; Zarattini, S.

doi:10.3390/universe7050132

Cited by 14 publications

(12 citation statements)

References 135 publications

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“…Thus, in this review, we do not make distinction between poor/loose and compact groups, and hereafter we simply refer to them as galaxy groups. The properties of fossil groups are instead discussed in the companion review by Aguerri & Zarattini (2021). However, since the optical properties are not always available, a threshold of M∼10 14 M , corresponding to a temperature of 2-3 keV, is also often used to classify these systems.…”

Section: Introductionmentioning

confidence: 99%

Scaling Properties of Galaxy Groups

et al. 2021

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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.

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Section: Introductionmentioning

confidence: 99%

Scaling Properties of Galaxy Groups

et al. 2021

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“…A galaxy group with a large magnitude gap is likely to have assembled its mass at an early epoch. Indeed, fossil groups, which are massive groups observationally selected on the basis of r−band magnitude gap, ∆m 12 > 2 mag and X-ray luminosity L X > 10 42 h −2 50 ergs −1 (Jones et al 2003), are considered to have assembled their mass earlier than non-fossil groups (D'Onghia et al 2005) or have lacked recent infall of new massive satellites (Kundert et al 2017) (See Aguerri & Zarattini (2021) for a recent review on fossil groups). Note that ∆m 12 is largely varied among nearby galaxy groups.…”

Section: Introductionmentioning

confidence: 99%

A Rich Satellite Population of the NGC 4437 Group and Implications of a Magnitude Gap for Galaxy Group Assembly History

Kim,

Kang,

Lee

et al. 2022

Preprint

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Both observations and cosmological simulations have recently shown that there is a large scatter in the number of satellites of Milky Way (MW)-like galaxies. In this study, we investigate the relation between the satellite number and galaxy group assembly history, using the r−band magnitude gap (∆m 12 ) between the first and the second brightest galaxy as an indicator. From 20 deg 2 of Hyper Suprime-Cam Subaru Strategic Program Wide layer, we identify 17 dwarf satellite candidates around NGC 4437, a spiral galaxy with about one-fourth of the MW stellar mass. We estimate their distances using the surface brightness fluctuation (SBF) method. Then we confirm five candidates as members of the NGC 4437 group, resulting in a total of seven group members. Combining the NGC 4437 group (with ∆m 12 = 2.5 mag) with other groups in the literature, we find a stratification of the satellite number by ∆m 12 for a given host stellar mass. The satellite number for given host stellar mass decreases as ∆m 12 increases. The same trend is found in simulated galaxy groups in IllustrisTNG50 simulations. We also find that the host galaxies in groups with a smaller ∆m 12 (like NGC 4437) have assembled their halo mass more recently than those in larger gap groups, and that their stellar-to-halo mass ratios (SHMRs) increase as ∆m 12 increases. These results show that the large scatter in the satellite number is consistent with a large range of ∆m 12 , indicating diverse group assembly histories.

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“…One such class of objects is comprised of fossil groups, which have been studied both observationally and in simulations over the last three decades (studies include e.g. Ponman et al 1994;Vikhlinin et al 1999;Jones et al 2000Jones et al , 2003D'Onghia et al 2005;D'Onghia et al 2007;von Benda-Beckmann et al 2008); for a recent review on FGs, see Aguerri & Zarattini (2021).…”

Section: Introductionmentioning

confidence: 99%

“…Historically, FGs have been interpreted in various ways, including: 1) that they are not a special class of halos, but rather represent the final stage of mass assembly for all group scale halos (e.g. La Barbera et al 2009;Ponman et al 1994); 2) that they are distinct in constituting the "oldest and most undisturbed galaxy systems not yet absorbed by larger halos" ( Santos et al (2007), see also Ponman et al (1994)); and 3) that FGs are simply "extreme systems produced following the current theory of structure formation in the universe" (Aguerri & Zarattini 2021). Although FGs have been studied for decades, there is still not a firm consensus regarding the place these objects hold in the wider picture of halo formation.…”

Section: Introductionmentioning

confidence: 99%

Cosmo-Paleontology: Statistics of Fossil Groups in a Gravity-Only Simulation

Cossairt,

Buehlmann,

Kovacs

et al. 2022

Preprint

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We present a detailed study of fossil group candidates identified in "Last Journey", a gravityonly cosmological simulation covering a (3.4 h −1 Gpc) 3 volume with a particle mass resolution of m p ≈ 2.7 × 10 9 h −1 M . The simulation allows us to simultaneously capture a large number of groupscale halos and to resolve their internal structure. Historically, fossil groups have been characterized by high X-ray brightness and a large luminosity gap between the brightest and second brightest galaxy in the group. In order to identify candidate halos that host fossil groups, we use halo merger tree information to introduce two parameters: a luminous merger mass threshold (M LM ) and a last luminous merger redshift cut-off (z LLM ). The final parameter choices are informed by observational data and allow us to identify a plausible fossil group sample from the simulation. The candidate halos are characterized by reduced substructure and are therefore less likely to host bright galaxies beyond the brightest central galaxy. We carry out detailed studies of this sample, including analysis of halo properties and clustering. We find that our simple assumptions lead to fossil group candidates that form early, have higher concentrations, and are more relaxed compared to other halos in the same mass range.

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Properties of Fossil Groups of Galaxies

Cited by 14 publications

References 135 publications

Scaling Properties of Galaxy Groups

Scaling Properties of Galaxy Groups

A Rich Satellite Population of the NGC 4437 Group and Implications of a Magnitude Gap for Galaxy Group Assembly History

Cosmo-Paleontology: Statistics of Fossil Groups in a Gravity-Only Simulation

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