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Universe
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Universe: Feature Papers 2024—"Galaxies and Clusters"
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Universe: Feature Papers 2024—"Galaxies and Clusters"

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

Deadline for manuscript submissions: 31 December 2024 | Viewed by 5927

Special Issue Editor

Dr. Mauro D’Onofrio

E-Mail Website
Guest Editor
Dipartimento di Fisica & Astronomia “Galileo Galilei”, Università di Padova, IT35122 Padova , Italy
Interests: galaxies: structure and evolution; galaxies: kinematics and dynamics; clusters: structure and evolution; active galactic nuclei; novae and supernovae

Special Issue Information

Dear Colleagues,

A new era of our knowledge of galaxies and clusters is opening today thanks to the new space/ground telescopes and the large deep surveys. New methods of data analysis are also in progress to manage this large flux of information.

This Universe special issue dedicated to "Galaxies and Clusters" aims to collect several research papers connected to such new observations of galaxies and clusters at all redshift as well as to the new invented methods used to reduce and analyze the data.

Dr. Mauro D’Onofrio
Guest Editor

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 submissions that pass pre-check are 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

  • galaxies and clusters
  • galaxy formation and evolution
  • the structure of galaxies
  • dwarf galaxies
  • star formation in galaxies
  • galaxy clustering
  • the halo of galaxies
  • galaxy satellites
  • dark matter in galaxies
  • lensing of galaxies
  • deep surface brightness images
  • galaxy counts
  • machine learning and artificial intelligence for galaxy/cluster analysis

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Published Papers (5 papers)

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Research

Jump to: Review

32 pages, 1586 KiB  
Article
The Magellanic Clouds Are Very Rare in the IllustrisTNG Simulations
by Moritz Haslbauer, Indranil Banik, Pavel Kroupa, Hongsheng Zhao and Elena Asencio
Universe 2024, 10(10), 385; https://doi.org/10.3390/universe10100385 - 1 Oct 2024
Cited by 1 | Viewed by 558
Abstract
The Large and Small Magellanic Clouds (LMC and SMC) form the closest interacting galactic system to the Milky Way, therewith providing a laboratory to test cosmological models in the local Universe. We quantify the likelihood for the Magellanic Clouds (MCs) to be observed [...] Read more.
The Large and Small Magellanic Clouds (LMC and SMC) form the closest interacting galactic system to the Milky Way, therewith providing a laboratory to test cosmological models in the local Universe. We quantify the likelihood for the Magellanic Clouds (MCs) to be observed within the ΛCDM model using hydrodynamical simulations of the IllustrisTNG project. The orbits of the MCs are constrained by proper motion measurements taken by the Hubble Space Telescope and Gaia. The MCs have a mutual separation of dMCs=24.5kpc and a relative velocity of vMCs=90.8kms−1, implying a specific phase-space density of fMCs,obs≡(dMCs·vMCs)−3=9.10×10−11km−3s3kpc−3. We select analogues to the MCs based on their stellar masses and distances in MW-like halos. None of the selected LMC analogues have a higher total mass and lower Galactocentric distance than the LMC, resulting in >3.75σ tension. We also find that the fMCs distribution in the highest resolution TNG50 simulation is in 3.95σ tension with observations. Thus, a hierarchical clustering of two massive satellites like the MCs in a narrow phase-space volume is unlikely in ΛCDM, presumably because of short merger timescales due to dynamical friction between the overlapping dark matter halos. We show that group infall led by an LMC analogue cannot populate the Galactic disc of satellites (DoS), implying that the DoS and the MCs formed in physically unrelated ways in ΛCDM. Since the 20∘ alignment of the LMC and DoS orbital poles has a likelihood of P=0.030 (2.17σ), adding this χ2 to that of fMCs gives a combined likelihood of P=3.90×10−5 (4.11σ). Full article
(This article belongs to the Special Issue Universe: Feature Papers 2024—"Galaxies and Clusters")
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25 pages, 2077 KiB  
Article
The Rotation of Classical Bulges in Barred Galaxies in the Presence of Gas
by Rubens E. G. Machado, Kenzo R. Sakamoto, Andressa Wille and Gustavo F. Gonçalves
Universe 2024, 10(5), 223; https://doi.org/10.3390/universe10050223 - 16 May 2024
Cited by 1 | Viewed by 976
Abstract
Barred galaxies often develop a box/peanut pseudobulge, but they can also host a nearly spherical classical bulge, which is known to gain rotation due to the bar. We aim to explore how the presence of gas impacts the rotation of classical bulges. We [...] Read more.
Barred galaxies often develop a box/peanut pseudobulge, but they can also host a nearly spherical classical bulge, which is known to gain rotation due to the bar. We aim to explore how the presence of gas impacts the rotation of classical bulges. We carried out a comprehensive set of hydrodynamical N-body simulations with different combinations of bulge masses and gas fractions. In these models, both massive bulges and high gas content tend to inhibit the formation of strong bars. For low-mass bulges, the resulting bar is stronger in cases of low gas content. In the stronger bar models, bulges acquire more angular momentum and thus display considerable rotational velocity. Such bulges also develop anisotropic velocity dispersions and become triaxial in shape. We found that the rotation of the bulge becomes less pronounced as the gas fraction is increased from 0 to 30%. These results indicate that the gas content has a significant effect on the dynamics of the classical bulge, because it influences bar strength. Particularly in the case of the low-mass bulges (10% bulge mass fraction), all of the measured rotational and structural properties of the classical bulge depend strongly and systematically on the gas content of the galaxy. Full article
(This article belongs to the Special Issue Universe: Feature Papers 2024—"Galaxies and Clusters")
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26 pages, 17785 KiB  
Article
The κ-Model under the Test of the SPARC Database
by Gianni Pascoli
Universe 2024, 10(3), 151; https://doi.org/10.3390/universe10030151 - 21 Mar 2024
Cited by 1 | Viewed by 1231
Abstract
Our main goal here is to conduct a comparative analysis between the well-known MOND theory and a more recent model called the κ-model. An additional connection, between the κ-model and two other novel MOND-type theories, Newtonian Fractional-Dimension Gravity (NFDG) and Refracted [...] Read more.
Our main goal here is to conduct a comparative analysis between the well-known MOND theory and a more recent model called the κ-model. An additional connection, between the κ-model and two other novel MOND-type theories, Newtonian Fractional-Dimension Gravity (NFDG) and Refracted Gravity (RG), is likewise presented. All these models are built to overtake the DM paradigm, or at least to strongly reduce the dark matter content. Whereas they rely on different formalisms, however, all four seem to suggest that the universal parameter, a0, appearing in MOND theory could intrinsically be correlated to either the sole baryonic mean mass density (RG and κ-model) and/or to the dimension of the object under consideration (NFDG and κ-model). We then confer to parameter a0 a more flexible status of multiscale parameter, as required to explain the dynamics together in galaxies and in galaxy clusters. Eventually, the conformal gravity theory (CFT) also seems to have some remote link with the κ-model, even though the first one is an extension of general relativity, and the second one is Newtonian in essence. The κ-model has been tested on a small sample of spiral galaxies and in galaxy clusters. Now, we test this model on a large sample of galaxies issued from the SPARC database. Full article
(This article belongs to the Special Issue Universe: Feature Papers 2024—"Galaxies and Clusters")
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19 pages, 1623 KiB  
Article
Dark Matter in Fractional Gravity III: Dwarf Galaxies Kinematics
by Francesco Benetti, Andrea Lapi, Giovanni Gandolfi, Minahil Adil Butt, Yacer Boumechta, Balakrishna S. Haridasu and Carlo Baccigalupi
Universe 2023, 9(11), 478; https://doi.org/10.3390/universe9110478 - 8 Nov 2023
Cited by 1 | Viewed by 1592
Abstract
Recently, we put forward a framework where the dark matter (DM) component within virialized halos is subject to a non-local interaction originated by fractional gravity (FG) effects. In previous works, we demonstrated that such a framework can substantially alleviate the small-scale issues of [...] Read more.
Recently, we put forward a framework where the dark matter (DM) component within virialized halos is subject to a non-local interaction originated by fractional gravity (FG) effects. In previous works, we demonstrated that such a framework can substantially alleviate the small-scale issues of the standard ΛCDM paradigm, without altering the DM mass profile predicted by N-body simulations, and retaining its successes on large cosmological scales. In this paper, we investigate further, to probe FG via the high-quality data of individual dwarf galaxies, by exploiting the rotation velocity profiles inferred from stellar and gas kinematic measurements in eight dwarf irregulars, and the projected velocity dispersion profiles inferred from the observed dynamics of stellar tracers in seven dwarf spheroidals and in the ultra-diffuse galaxy DragonFly 44. We find that FG can reproduce extremely well the rotation and dispersion curves of the analyzed galaxies, performing in most instances significantly better than the standard Newtonian setup. Full article
(This article belongs to the Special Issue Universe: Feature Papers 2024—"Galaxies and Clusters")
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Review

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39 pages, 1533 KiB  
Review
The Correlation Luminosity-Velocity Dispersion of Galaxies and Active Galactic Nuclei
by Mauro D’Onofrio, Paola Marziani, Cesare Chiosi and Castalia Alenka Negrete
Universe 2024, 10(6), 254; https://doi.org/10.3390/universe10060254 - 4 Jun 2024
Viewed by 1061
Abstract
In this work we discuss the correlation between luminosity L and velocity dispersion σ observed in different astrophysical contexts, in particular that of early-type galaxies (ETGs; Faber–Jackson (FJ) law) and that of active galactic nuclei (AGN). Our data for the ETGs confirm the [...] Read more.
In this work we discuss the correlation between luminosity L and velocity dispersion σ observed in different astrophysical contexts, in particular that of early-type galaxies (ETGs; Faber–Jackson (FJ) law) and that of active galactic nuclei (AGN). Our data for the ETGs confirm the bending of the FJ at high masses and the existence of similar curvatures in the projections of the Fundamental Plane (FP) approximately at the mass scale of ∼1010M⊙. We provide an explanation for such curvatures and for the presence of the Zone of Exclusion (ZoE) in these diagrams. The new prospected theory for the FJ law introduces a new framework to understand galaxy evolution in line with the hierarchical structure of the Universe. The classic analysis carried out for a class of type 1 AGN accreting gas at very high rates, confirms that a FJ law of the form L=L0σ4 is roughly consistent with the observations, with a slope quite similar to that of ETGs. We discuss the physics behind the FJ law for the AGN in different contexts and also examine the biases affecting both the luminosity and the velocity dispersion, paying particular attention to the effects induced by the spherical symmetry of the emitting sources on the accuracy of the luminosity estimates. Full article
(This article belongs to the Special Issue Universe: Feature Papers 2024—"Galaxies and Clusters")
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