Article
Astronomy & Astrophysics
Adriana Bariego-Quintana, Felipe J. Llanes-Estrada, Oliver Manzanilla Carretero
Summary: The flattening rotation velocity v(r) -> constant discovered by Rubin and collaborators in the SPARC galaxy-rotation data is in line with Kepler's law in one less dimension. Elongated dark matter distributions, with their axis of prolateness perpendicular to the galactic plane, naturally reproduce this phenomenon. Detailed fits to the rotation data also support this theoretical understanding, showing that elongated distributions provide a better fit than purely spherical ones.
Article
Astronomy & Astrophysics
Antonio De Felice, Shinji Mukohyama
Summary: This paper introduces a new cosmological framework integrating dark matter into a minimally modified gravity model, maintaining the same number of gravitational degrees of freedom through a series of transformations. The framework includes two time-dependent free functions to achieve desired evolutions of Hubble expansion rate and effective gravitational constant for dark matter.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
J. Vega-Ferrero, J. M. Dana, J. M. Diego, G. Yepes, W. Cui, M. Meneghetti
Summary: The study compares the statistics and morphology of giant arcs in galaxy clusters using different models, finding that self-interacting dark matter produces fewer but more magnified arcs. The probability of interaction is higher in colliding clusters and in denser regions.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Hooman Davoudiasl, Peter B. Denton, David A. McGady
Summary: The conventional lore excludes fermionic dark matter with mass lighter than a few hundred electronvolts based on the Pauli exclusion principle. A new method is proposed in this paper which involves numerous quasi-degenerate species of fermions without couplings to the standard model to evade this bound. Gravitational interactions impose constraints from measurements at the LHC, cosmic rays, supernovae, and black hole spins and lifetimes, with a particular limit on the number of distinct species of particles being less than or around 10^62.
Article
Astronomy & Astrophysics
Andrea Maccio, Daniel Huterer Prats, Keri L. Dixon, Tobias Buck, Stefan Waterval, Nikhil Arora, Stephane Courteau, Xi Kang
Summary: Through simulations, it has been shown that dwarf galaxies can lose up to 80% of their dark matter content and see a significant change in the dark matter-to-stellar mass ratio after interactions with central galaxies. These findings align with observations of NGC 1052-DF2 and NGC 1054-DF4.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Miguel Aparicio Resco, Antonio L. Maroto
Summary: The study analyzes how to parametrize general modifications of the dark matter perturbations equations in a model-independent way, and shows that a general model with an imperfect and non-conserved dark matter fluid in a modified gravity scenario can be described with five general functions. It focuses on the sub-Hubble regime and finds that observable power spectra are sensitive to only three combinations of the initial five functions, which can help determine whether a modification of gravity or an imperfect/non-conserved dark matter is present. A Fisher forecast analysis for these three parameters is performed, with an example shown for a specific model with shear viscosity.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Charles Thorpe-Morgan, Denys Malyshev, Christoph-Alexander Stegen, Andrea Santangelo, Josef Jochum
Summary: This study reports on a search for dark matter in galaxy clusters using Fermi/LAT data, presenting constraints on the annihilation cross-section for different channels and discussing the potential impact of substructures and uncertainties on the results. The obtained limits are comparable to the best available limits based on observations of dwarf spheroidal galaxies with Fermi/LAT.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Han Aung, Daisuke Nagai, Erwin T. Lau
Summary: Recent studies have found discrepancies between the location of the accretion shock and the splashback radius of dark matter, with the former being larger by 20-100%. This has implications for multiwavelength studies of galaxy clusters.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Alvaro de la Cruz Dombriz, Francisco Jose Maldonado Torralba, David F. Mota
Summary: The stable pseudo-scalar degree of freedom in the quadratic Poincare Gauge theory of gravity is identified as a suitable candidate for dark matter. The study determines the parameter space in the theory that can explain all predicted cold dark matter phenomena and constrains these parameters with astrophysical observations.
Article
Astronomy & Astrophysics
Jessica E. Doppel, Laura Sales, Julio F. Navarro, Mario G. Abadi, Eric W. Peng, Elisa Toloba, Felipe Ramos-Almendares
Summary: The study found that using globular clusters (GCs) to estimate mass may result in biases in some cases, requiring calibration; some dwarf galaxies have GC velocity dispersion similar to the ultra-diffuse galaxy NGC 1052-DF2, suggesting extreme tidal mass loss as a possible formation channel for ultra-diffuse objects.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Rebecca K. Leane, Tim Linden, Payel Mukhopadhyay, Natalia Toro
Summary: This passage discusses a new scenario in which celestial bodies can enhance the efficiency of dark matter annihilation events, leading to distinctive annihilation signals. By analyzing data from Fermi and H.E.S.S., new constraints on the dark matter-nucleon scattering cross section for different mass scales of dark matter can be set.
Article
Astronomy & Astrophysics
Jiwon Jesse Han, Rohan P. Naidu, Charlie Conroy, Ana Bonaca, Dennis Zaritsky, Nelson Caldwell, Phillip Cargile, Benjamin D. Johnson, Vedant Chandra, Joshua S. Speagle, Yuan-Sen Ting, Turner Woody
Summary: This paper studies the ancient merger debris in the stellar halo, finding that long-lived structures HAC and VOD are associated with GSE, and the dark matter halo of the Galaxy is tilted and aligned with HAC-VOD. Such halo-disk misalignment is common in modern cosmological simulations. In addition, the relationship between the local and global stellar halo is analyzed.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Moritz Haslbauer, Pavel Kroupa, Akram Hasani Zonoozi, Hosein Haghi
Summary: The James Webb Space Telescope has discovered luminous high-redshift galaxy candidates, and by comparing them with the lambda CDM model, it is found that the stellar mass buildup in the early universe is more efficient than predicted.
ASTROPHYSICAL JOURNAL LETTERS
(2022)
Article
Astronomy & Astrophysics
Richard E. Griffiths, Mitchell Rudisel, Jenny Wagner, Timothy Hamilton, Po-Chieh Huang, Carolin Villforth
Summary: We reported the discovery of a 'folded' gravitationally lensed image, 'Hamilton's Object', found near an active galactic nucleus, which showed unique surface brightness features and stretched properties. The lensed images are sourced by a galaxy at a spectroscopic redshift and form a fold configuration on a caustic caused by a foreground galaxy cluster. The analysis suggests a mass density that hardly varies on an arcsecond scale over the areas covered by the multiple images.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
D. Eckert, S. Ettori, A. Robertson, R. Massey, E. Pointecouteau, D. Harvey, I. G. McCarthy
Summary: The distribution of dark matter in the cold dark matter paradigm fits well with the Einasto profile, while self-interacting dark matter leads to flatter mass density profiles. Researchers measured the structural properties of massive galaxy clusters and found that the measurements are consistent with the predictions of the cold dark matter paradigm. The self-interaction cross section of dark matter is found to be lower than what is required to solve the core-cusp problem in dwarf spheroidal galaxies.
ASTRONOMY & ASTROPHYSICS
(2022)
Editorial Material
Physics, Particles & Fields
Gonzalo J. Olmo, P. J. Porfirio
Summary: It is claimed in [1] that the existence of a Pontryagin term in the action of the Einstein-Palatini gravity theory disproves the conclusions of [2], which state that only in the case of Lovelock gravity are the metric and metric-affine formulations of gravity equivalent. However, it is shown that the addition of a Pontryagin term (or any other D-divergence) only affects the boundary and does not change the field equations and their solutions, which are those of General Relativity in the Palatini formalism. Therefore, the example provided in [1] is not a valid counterexample to [2].
Article
Astronomy & Astrophysics
M. G. Dainotti, G. Bargiacchi, A. L. Lenart, S. Nagataki, S. Capozziello
Summary: Currently, the cold dark matter model along with a cosmological constant is the best representation of the universe. However, we lack information in the high-redshift region and the study of quasars up to z = 7.54 has provided important insights into the matter density parameter omega( M ). This demonstrates the reliability of quasars as standard cosmological candles.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
Aleksander Lukasz Lenart, Giada Bargiacchi, Maria Giovanna Dainotti, Shigehiro Nagataki, Salvatore Capozziello
Summary: By studying high-redshift objects such as quasars, the value of the Hubble constant can be corrected, which can help resolve the current discrepancy between the cosmic microwave background radiation and the value obtained from Type Ia supernovae observations.
ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES
(2023)
Article
Physics, Mathematical
Salvatore Capozziello, Maurizio Capriolo, Gaetano Lambiase
Summary: The issue of defining gravitational energy in a given spatial region is still unresolved in General Relativity, except for particular cases of localized objects. In this study, we generalize the Einstein gravitational energy-momentum pseudotensor to non-local theories of gravity and consider analytic functions of the non-local integral operator ?(-1). By applying the Noether theorem to a gravitational Lagrangian invariant under infinitesimal rigid translations, we define a gravitational energy-momentum pseudotensor that transforms like a tensor under affine transformations. This pseudotensor, along with the energy-momentum complex, can be derived using the continuity equations considering gravitational and matter components, and their weak field limit is performed for astrophysical applications.
INTERNATIONAL JOURNAL OF GEOMETRIC METHODS IN MODERN PHYSICS
(2023)
Article
Astronomy & Astrophysics
S. Capozziello, S. Zare, D. F. Mota, H. Hassanabadi
Summary: In this study, the effects of a dark matter spike near the supermassive black hole in M87 (Virgo A galaxy) were investigated using the Bumblebee Gravity theory. The aim was to determine the impact of spontaneous Lorentz symmetry breaking on the horizon, ergo-region, and shadow of the Kerr Bumblebee black hole in the spike region. Dark matter distribution was incorporated into a Lorentz-violating spherically symmetric space-time, and the resulting solution was generalized to a Kerr Bumblebee black hole. The shapes of the shadow were examined based on observational data for the dark matter spike density and radius.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Ana Rita Ribeiro, Daniele Vernieri, Francisco S. N. Lobo
Summary: General Relativity is successful for weak gravitational fields but fails at high energies, like the initial singularity. Quantum Gravity is expected to provide insights into this problem. Loop Quantum Cosmology offers an alternative scenario to the Big Bang, avoiding the singularity and predicting a collapse to expansion through a bounce. This study uses metric f(R) gravity to reproduce modified Friedmann equations in the context of modified loop quantum cosmologies.
Article
Astronomy & Astrophysics
Salvatore Capozziello, Gamal G. L. Nashed
Summary: We derive a novel class of four-dimensional black hole solutions in Gauss-Bonnet gravity coupled with a scalar field in the presence of Maxwell electrodynamics. The choice of metric ansatz and the presence of the scalar field lead to the emergence of higher-order terms and the creation of monopoles in the metric potentials. The computed invariants associated with the black holes show soft singularities and the solutions exhibit multiple horizons depending on the spacetime.
CLASSICAL AND QUANTUM GRAVITY
(2023)
Article
Astronomy & Astrophysics
Gonzalo J. Olmo, Joao Luis Rosa, Diego Rubiera-Garcia, Diego Saez-Chillon Gomez
Summary: The optical appearance of a compact body with an unstable bound orbit surrounded by an accretion disk is dominated by a luminous ring known as the shadow. The Event Horizon Telescope (EHT) Collaboration has confirmed the rough details of this picture through imaging of supermassive central objects in M87 and the Milky Way. Testing a family of solutions within the Eddington-inspired Born-Infeld theory of gravity, we use the features of the ring and shadow to analyze the differences between black holes and traversable wormholes.
CLASSICAL AND QUANTUM GRAVITY
(2023)
Article
Astronomy & Astrophysics
Marcello Miranda, Daniele Vernieri, Salvatore Capozziello, Valerio Faraoni
Summary: The physical nature of Horndeski gravity is explained as a dissipative effective fluid in a new approach. Requiring the constitutive equations of a Newtonian fluid restricts the theory to two subclasses of viable Horndeski gravity. A linear stress-energy tensor of the Horndeski effective fluid is sufficient for gravitational waves to propagate at light speed, while other Horndeski theories correspond to exotic non-Newtonian effective fluids. The two linear Horndeski classes are further studied in the framework of first-order thermodynamics of viscous fluids.
GENERAL RELATIVITY AND GRAVITATION
(2023)
Article
Astronomy & Astrophysics
Hoang Ky Nguyen, Francisco S. N. Lobo
Summary: This paper introduces the recently obtained special Buchdahl-inspired metric, with focuses on the construction of the Kruskal-Szekeres diagram and the emergence of wormholes. The study finds that the wormhole structure allows for the formation of closed timelike curves (CTCs).
Article
Astronomy & Astrophysics
Matteo Califano, Ivan de Martino, Daniele Vernieri, Salvatore Capozziello
Summary: We investigate four cosmological models that may solve the Hubble tension by considering different dark energy equation of state. By creating mock catalogs and extracting events associated with possible electromagnetic counterpart, we estimate the precision to which the Einstein Telescope can bound the cosmological parameters. Our results show that the uncertainty in the Hubble constant is always below 1%, potentially offering a solution to the Hubble tension. The accuracy on other cosmological parameters is comparable to current methods, except for the emergent dark energy model where the Einstein Telescope alone can significantly improve the limits.
Article
Astronomy & Astrophysics
Renan B. Magalhaes, Andreu Maso-Ferrando, Gonzalo J. Olmo, Luis C. B. Crispino
Summary: In this study, we investigate the scalar absorption spectrum of wormhole solutions constructed using the thin-shell formalism for Palatini f(R) gravity. These wormholes result from the matching of two Reissner-Nordstrom spacetimes at a timelike hypersurface (shell), which can be stable and have positive or negative energy density according to the junction conditions in Palatini f(R). We identify a novel configuration made up of two overcharged Reissner-Nordstrom spacetimes, which exhibits a different absorption profile compared to black holes and previously studied wormholes across the entire frequency range.
Article
Astronomy & Astrophysics
Ester Piedipalumbo, Stefano Vignolo, Pasquale Feola, Salvatore Capozziello
Summary: In this study, we investigate the non-flat interacting quintessence cosmology within the framework of scalar-tensor gravity, where a scalar field interacts with dark matter. By employing the Noether Symmetry Approach, we obtain general exact solutions for cosmological equations and determine the scalar-field self-interaction potentials. The obtained solutions are capable of reproducing the accelerated expansion of the Universe and are consistent with various observational datasets, including the SNeIa Pantheon data, gamma ray bursts Hubble diagram, and direct measurements of the Hubble parameter.
PHYSICS OF THE DARK UNIVERSE
(2023)
Article
Astronomy & Astrophysics
Tomi Koivisto, Tom Zlosnik
Summary: In special-relativistic physics, the fixed metric tensor of spacetime is proposed to be promoted to a dynamical field in order to develop a gravitational theory. Another description of special-relativistic physics suggests the inclusion of scalar fields that can dynamically take the form of inertial coordinates, without a fixed spacetime geometry. This alternative approach to gravity introduces gauge fields to promote the invariance of actions under global or local transformations, leading to gravitational theories with similarities and differences to general relativity. Among these theories, the one based on local Lorentz symmetry extends general relativity and allows for the introduction of a standard of time into the dynamics of the gravitational field, even with a non-zero curvature.
Article
Astronomy & Astrophysics
Tomi S. Koivisto
Summary: Symmetric teleparallel gravity is proved to be integrable with the existence of boundaries, when constraints are consistently implemented in the covariant phase space formalism.