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16 pages, 14681 KiB

Open AccessFeature PaperArticle

Galaxy Groups as the Ultimate Probe of AGN Feedback

by Dominique Eckert, Fabio Gastaldello, Ewan O’Sullivan, Alexis Finoguenov, Marisa Brienza and the X-GAP Collaboration

Galaxies 2024, 12(3), 24; https://doi.org/10.3390/galaxies12030024 - 13 May 2024

Cited by 4 | Viewed by 1422

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. The outflows from the central engine tightly couple with the surrounding gaseous medium and provide the dominant heating source, preventing runaway cooling. Every major modern hydrodynamical simulation suite now includes a prescription for AGN feedback to reproduce the realistic populations of galaxies. However, the mechanisms governing the feeding/feedback cycle between the central black holes and their surrounding galaxies and halos are still poorly understood. Galaxy groups are uniquely suited to constrain the mechanisms governing the cooling–heating balance, as the energy supplied by the central AGN can exceed the gravitational binding energy of halo gas particles. Here, we provide a brief overview of our knowledge of the impact of AGN on the hot atmospheres of galaxy groups, with a specific focus on the thermodynamic profiles of the groups. We then present our on-going efforts to improve on the implementation of AGN feedback in galaxy evolution models by providing precise measurements of the properties of galaxy groups. We introduce the XMM-Newton Group AGN Project (X-GAP), a large program on XMM-Newton targeting a sample of 49 galaxy groups out to

R_{500 c}

. Full article

(This article belongs to the Special Issue Multi-Phase Fueling and Feedback Processes in Jetted AGN)

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Review

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16 pages, 1306 KiB

Open AccessReview

Investigating the Properties of the Relativistic Jet and Hot Corona in AGN with X-ray Polarimetry

by Dawoon E. Kim, Laura Di Gesu, Frédéric Marin, Alan P. Marscher, Giorgio Matt, Paolo Soffitta, Francesco Tombesi, Enrico Costa and Immacolata Donnarumma

Galaxies 2024, 12(3), 20; https://doi.org/10.3390/galaxies12030020 - 23 Apr 2024

Cited by 1 | Viewed by 1321

Abstract

X-ray polarimetry has been suggested as a prominent tool for investigating the geometrical and physical properties of the emissions from active galactic nuclei (AGN). The successful launch of the Imaging X-ray Polarimetry Explorer (IXPE) on 9 December 2021 has expanded the previously restricted [...] Read more.

X-ray polarimetry has been suggested as a prominent tool for investigating the geometrical and physical properties of the emissions from active galactic nuclei (AGN). The successful launch of the Imaging X-ray Polarimetry Explorer (IXPE) on 9 December 2021 has expanded the previously restricted scope of polarimetry into the X-ray domain, enabling X-ray polarimetric studies of AGN. Over a span of two years, IXPE has observed various AGN populations, including blazars and radio-quiet AGN. In this paper, we summarize the remarkable discoveries achieved thanks to the opening of the new window of X-ray polarimetry of AGN through IXPE observations. We will delve into two primary areas of interest: first, the magnetic field geometry and particle acceleration mechanisms in the jets of radio-loud AGN, such as blazars, where the relativistic acceleration process dominates the spectral energy distribution; and second, the geometry of the hot corona in radio-quiet AGN. Thus far, the IXPE results from blazars favor the energy-stratified shock acceleration model, and they provide evidence of helical magnetic fields inside the jet. Concerning the corona geometry, the IXPE results are consistent with a disk-originated slab-like or wedge-like shape, as could result from Comptonization around the accretion disk. Full article

(This article belongs to the Special Issue Multi-Phase Fueling and Feedback Processes in Jetted AGN)

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16 pages, 6667 KiB

Open AccessFeature PaperReview

The Seeding of Cosmic Ray Electrons by Cluster Radio Galaxies: A Review

by Franco Vazza and Andrea Botteon

Galaxies 2024, 12(2), 19; https://doi.org/10.3390/galaxies12020019 - 22 Apr 2024

Cited by 7 | Viewed by 1261

Abstract

Radio galaxies in clusters of galaxies are a prominent reservoir of magnetic fields and of non-thermal particles, which become mixed with the intracluster medium. We review the observational and theoretical knowledge of the role of these crucial ingredients for the formation of diffuse [...] Read more.

Radio galaxies in clusters of galaxies are a prominent reservoir of magnetic fields and of non-thermal particles, which become mixed with the intracluster medium. We review the observational and theoretical knowledge of the role of these crucial ingredients for the formation of diffuse radio emission in clusters (radio halos, relics, mini halos) and outline the open questions in this field. Full article

(This article belongs to the Special Issue Multi-Phase Fueling and Feedback Processes in Jetted AGN)

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30 pages, 1896 KiB

Open AccessReview

Observational Tests of Active Galactic Nuclei Feedback: An Overview of Approaches and Interpretation

by Chris M. Harrison and Cristina Ramos Almeida

Galaxies 2024, 12(2), 17; https://doi.org/10.3390/galaxies12020017 - 10 Apr 2024

Cited by 30 | Viewed by 2275

Abstract

Growing supermassive black holes (Active Galactic Nuclei; AGN) release energy with the potential to alter their host galaxies and larger-scale environment; a process named “AGN feedback”. Feedback is a required component of galaxy formation models and simulations to explain the observed properties of [...] Read more.

Growing supermassive black holes (Active Galactic Nuclei; AGN) release energy with the potential to alter their host galaxies and larger-scale environment; a process named “AGN feedback”. Feedback is a required component of galaxy formation models and simulations to explain the observed properties of galaxy populations. We provide a broad overview of observational approaches that are designed to establish the physical processes that couple AGN energy to the multi-phase gas, or to find evidence that AGN impact upon galaxy evolution. The orders-of-magnitude range in spatial, temporal, and temperature scales, requires a diverse set of observational studies. For example, studying individual targets in detail sheds light on coupling mechanisms; however, evidence for the long-term impact of AGN is better established within galaxy populations that are not necessarily currently active. We emphasise how modern surveys have revealed the importance of radio emission for identifying and characterising feedback mechanisms. At the achieved sensitivities, the detected radio emission can trace a range of processes, including a shocked interstellar medium caused by AGN outflows (driven by various mechanisms including radiation pressure, accretion disc winds, and jets). We also describe how interpreting observations in the context of theoretical work can be challenging, in part, due to some of the adopted terminology. Full article

(This article belongs to the Special Issue Multi-Phase Fueling and Feedback Processes in Jetted AGN)

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13 pages, 1202 KiB

Open AccessReview

Impact of Active Galactic Nuclei Feedback on the Dynamics of Gas: A Review across Diverse Environments

by Mojtaba Raouf, Mohammad Hossein Purabbas and Fatemeh Fazel Hesar

Galaxies 2024, 12(2), 16; https://doi.org/10.3390/galaxies12020016 - 8 Apr 2024

Viewed by 1295

Abstract

This review examines the relationship between black hole activity and kinematic gas–star misalignment in brightest group galaxies (BGGs) with different merger rates. The formation history of galaxy groups is assessed through “age-dating” as an indicator of distinct major mergers involving the BGGs. BGGs [...] Read more.

This review examines the relationship between black hole activity and kinematic gas–star misalignment in brightest group galaxies (BGGs) with different merger rates. The formation history of galaxy groups is assessed through “age-dating” as an indicator of distinct major mergers involving the BGGs. BGGs within groups characterized by a higher frequency of major mergers are more likely to host active SMBHs. A consistent correlation is identified between the level of black hole activity, as indicated by the 1.4 GHz and 325 MHz radio emissions, and the degree of kinematic misalignment between the gas and stellar components in BGGs. In dynamically fossil groups, where black hole accretion rate is relatively (∼1 dex) lower due to the lack of recent (≤1 Gyr) major mergers, there is reduced (∼30%) misalignment between the gas and stellar components of BGGs compared to non-fossil groups. Additionally, this study reveals that BGGs in non-fossil groups show higher levels of star formation rate and increased occurrence of mergers, contributing to observed color differences. Exploring the properties and dynamics of the gas disk influenced by mechanical AGN feedback through hydrodynamic simulations suggests that AGN wind-induced effects further lead to the persistent gas misalignment in the disk around the supermassive black hole. Full article

(This article belongs to the Special Issue Multi-Phase Fueling and Feedback Processes in Jetted AGN)

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15 pages, 2560 KiB

Open AccessReview

AGN Feedback Signatures in UV Emission

by K. Rubinur

Galaxies 2024, 12(2), 15; https://doi.org/10.3390/galaxies12020015 - 4 Apr 2024

Cited by 2 | Viewed by 1671

Abstract

Supermassive black holes (SMBH) are believed to influence galaxy evolution through AGN (active galactic nuclei) feedback. Galaxy mergers are key processes of galaxy formation that lead to AGN activity and star formation. The relative contribution of AGN feedback and mergers to star formation [...] Read more.

Supermassive black holes (SMBH) are believed to influence galaxy evolution through AGN (active galactic nuclei) feedback. Galaxy mergers are key processes of galaxy formation that lead to AGN activity and star formation. The relative contribution of AGN feedback and mergers to star formation is not yet well understood. In radio-loud objects, AGN outflows are dominated by large jets. However, in radio-quiet objects, outflows are more complex and involve jet, wind, and radiation. In this review, we discuss the signatures of AGN feedback through the alignment of radio and UV emissions. Current research on AGN feedback is discussed, along with a few examples of studies such as the galaxy merger system MRK 212, the radio-quiet AGN NGC 2639, and the radio-loud system Centaurus A. Multi-frequency observations of MRK 212 indicate the presence of dual AGN, as well as feedback-induced star-forming UV clumps. The fourth episode of AGN activity was detected in radio observations of the Seyfert galaxy NGC 2639, which also showed a central cavity of 6 kpc radius in CO and UV maps. This indicates that multi-epoch jets of radio-quiet AGN can blow out cold molecular gas, which can further reduce star formation in the center of the galaxies. Recent UV observations of Cen A have revealed two sets of stellar population in the northern star-forming region, which may have two different origins. Recent studies have shown that there is evidence that both positive and negative feedback can be present in galaxies at different scales and times. High-resolution, multi-band observations of large samples of different types of AGN and their host galaxies are important for understanding the two types of AGN feedback and their effect on the host galaxies. Future instruments like INSIST and UVEX will be able to help achieve some of these goals. Full article

(This article belongs to the Special Issue Multi-Phase Fueling and Feedback Processes in Jetted AGN)

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16 pages, 2724 KiB

Open AccessReview

What Have We Learned about the Life Cycle of Radio Galaxies from New Radio Surveys

by Raffaella Morganti

Galaxies 2024, 12(2), 11; https://doi.org/10.3390/galaxies12020011 - 13 Mar 2024

Viewed by 1966

Abstract

The recurrent activity of radio AGN, with phases of activity alternating with periods of quiescence, has been known since the early studies of these objects. The full relevance of this cycle is emphasised by the requirement, from the AGN feedback scenario, of a [...] Read more.

The recurrent activity of radio AGN, with phases of activity alternating with periods of quiescence, has been known since the early studies of these objects. The full relevance of this cycle is emphasised by the requirement, from the AGN feedback scenario, of a recurrent impact of the energy released by the SMBH during the lifetime of the host galaxy: only in this way can AGN feedback influence galaxy evolution. Radio AGN in different evolutionary phases can be identified by their properties, like morphology and spectral indices. Dying/remnant and restarted sources have been the most elusive to select and characterise, but they are crucial to quantify the full life cycle. Thanks to the availability of new, large radio surveys (particularly at low frequencies), it is finally possible to make a more complete census of these rare sources and start building larger samples. This paper gives an overview of the recent work conducted using a variety of radio telescopes and surveys, highlighting some of the new results characterising the properties of dying/remnant and restarted radio sources and what has been learned about the life cycle of radio AGN. The comparison with the predictions from numerical simulations is also discussed. The results so far show that remnant and restarted radio AGN have a variety of properties which make these objects more complex than previously thought. Full article

(This article belongs to the Special Issue Multi-Phase Fueling and Feedback Processes in Jetted AGN)

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11 pages, 3280 KiB

Open AccessReview

Fueling Processes on (Sub-)kpc Scales

by Francoise Combes

Galaxies 2023, 11(6), 120; https://doi.org/10.3390/galaxies11060120 - 13 Dec 2023

Cited by 1 | Viewed by 1668

Abstract

Since the 1970s, astronomers have struggled with the issue of how matter can be accreted to promote black-hole growth. While low-angular-momentum stars may be devoured by a black hole, they are not a sustainable source of fuel. Gas, which could potentially provide an [...] Read more.

Since the 1970s, astronomers have struggled with the issue of how matter can be accreted to promote black-hole growth. While low-angular-momentum stars may be devoured by a black hole, they are not a sustainable source of fuel. Gas, which could potentially provide an abundant fuel source, presents another challenge due to its enormous angular momentum. While viscous torques are not significant, gas is subject to gravity torques from non-axisymmetric potentials such as bars and spirals. Primary bars can exchange angular momentum with the gas within corotation, causing it to spiral inwards until reaching the inner Lindblad resonance. An embedded nuclear bar can then take over. As the gas reaches the black hole’s sphere of influence, the torque becomes negative, fueling the center. Dynamical friction also accelerates the infall of gas clouds closer to the nucleus. However, because of the Eddington limit, growing a black hole from a stellar-mass seed is a slow process. The existence of very massive black holes in the early universe remains a puzzle that could potentially be solved through direct collapse of massive clouds into black holes or super-Eddington accretion. Full article

(This article belongs to the Special Issue Multi-Phase Fueling and Feedback Processes in Jetted AGN)

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