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We consider the observational signatures of thin accretion disks around a reflection-asymmetric traversable thin-shell wormhole. This wormhole, built in the framework of Palatini $f(R)$ gravity coupled to a Maxwell field using a junction…

General Relativity and Quantum Cosmology · Physics 2026-02-27 Caio F. B. Macedo , João Luís Rosa , Diego Rubiera-Garcia , Alejandro Rueda

We constrain the physical nature of dark matter using the newly identified massive merging galaxy cluster MACSJ0025.4-1222. As was previously shown by the example of the Bullet Cluster (1E0657-56), such systems are ideal laboratories for…

We explore the dark matter distribution in ms1224.7+2007 using the gravitational distortion of the images of faint background galaxies. Projected mass image reconstruction reveals a highly significant concentration coincident with the X-ray…

Astrophysics · Physics 2009-10-22 G. G. Fahlman , Nick Kaiser , Gordon Squires , David Woods

I start with a brief introduction to MOND phenomenology and its possible roots in cosmology--a notion that may turn out to be the most far reaching aspect of MOND. Next I discuss the implications of MOND for the dark matter (DM) doctrine:…

Astrophysics · Physics 2009-06-23 Mordehai Milgrom

Simulated images of a black hole surrounded by optically thin emission typically display two main features: a central brightness depression and a narrow, bright "photon ring" consisting of strongly lensed images superposed on top of the…

High Energy Astrophysical Phenomena · Physics 2021-09-08 Andrew Chael , Michael D. Johnson , Alexandru Lupsasca

The dark matter in Galactic halos, or some fraction of it, may be in the form of dark clusters which consist of small mass objects. Carr & Lacey (1987) have derived the permissible properties of such systems, and proposed the existence of…

Astrophysics · Physics 2009-10-22 Eyal Maoz

We study the mass distribution of galaxy clusters in Milgromian dynamics, or modified Newtonian dynamics (MOND). We focus on five galaxy clusters from the X-COP sample, for which high-quality data are available on both the baryonic mass…

Cosmology and Nongalactic Astrophysics · Physics 2024-05-17 Ruth Kelleher , Federico Lelli

We propose that several short duration events observed in past stellar occultations by Chiron were produced by rings material. From a reanalysis of the stellar occultation data in the literature we determined two possible orientations of…

I consider the observed rotation curves of 12 gas-dominated low-surface-brightness galaxies -- objects in which the mass of gas ranges between 2.2 and 27 times the mass of the stellar disk (mean=9.4). This means that, in the usual…

Astrophysics of Galaxies · Physics 2019-02-20 R. H. Sanders

Odd Radio Circles (ORCs) are unexpected faint circles of diffuse radio emission discovered in recent wide deep radio surveys. They are typically about one arcmin in diameter, and may be spherical shells of synchrotron emission about a…

Astrophysics of Galaxies · Physics 2021-11-03 Ray P. Norris , Evan Crawford , Peter Macgregor

Gerhard had recently analyzed the data on seven dwarf spheroidals, and concluded that these disagree with the predictions of MOND. We contend that this conclusion is anything but correct. With new data for three of the dwarfs the…

Astrophysics · Physics 2016-08-30 Mordehai Milgrom

The ubiquitous presence of dark matter in the universe is today a central tenet in modern cosmology and astrophysics. Ranging from the smallest galaxies to the observable universe, the evidence for dark matter is compelling in dwarfs,…

Astrophysics of Galaxies · Physics 2015-03-16 Fabio Iocco , Miguel Pato , Gianfranco Bertone

We have observed IRAS06468-0325 obtaining optical and infrared images through IJHKs and L' filters, K-band low-resolution spectroscopy, together with millimetre line observations of CO and CS. IRAS06468-0325 has a very unusual and enigmatic…

Astrophysics · Physics 2009-11-13 Joao L. Yun , Jose M. Torrelles , Nuno C. Santos

The evidence of the phenomenon for which, in galaxies, the gravitating mass is distributed differently than the luminous mass, increases as new data become available. Furthermore, this discrepancy is well structured and it depends on the…

Astrophysics of Galaxies · Physics 2019-03-11 Paolo Salucci

We present a simulated cluster of galaxies, modeled with a pre-heated intracluster medium, that exhibits X-ray features similar to the `cold fronts' seen in Chandra observations. Mock observations at a particular epoch show factor two…

Astrophysics · Physics 2009-11-07 John J. Bialek , August E. Evrard , Joseph J. Mohr

Genzel et al. have recently published the rotation curves of six high-redshift disc galaxies ($z\sim 0.9-2.4$), which they find to be `baryon dominated' within the studies radii. While not up to the standard afforded by data available for…

Astrophysics of Galaxies · Physics 2017-04-26 Mordehai Milgrom

A device consisted of a set of circular rings, the centers of which lie on an axis, behaves like a solenoid when the ratio of its radius and distance between two successive rings is greater than one. As this ratio decreases, the device…

Classical Physics · Physics 2021-02-03 Y. Contoyiannis , M. Kampitakis

We perform a set of non-radiative hydrodynamical simulations of merging spherical halos in order to understand the angular momentum (AM) properties of the galactic halos seen in cosmological simulations. The universal shape of AM…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-04 Sanjib Sharma , Matthias Steinmetz , Joss Bland-Hawthorn

I consider in light of MOND the three debris galaxies discussed recently by Bournaud et al.. These exhibit mass discrepancies of a factor of a few within several scale lengths of the visible galaxy, which, arguably, flies in the face of the…

Astrophysics · Physics 2009-11-13 Mordehai Milgrom

The recently discovered ring of stars near Galactocentric distance $r = 20$ kpc is interpreted as baryonic matter accreted onto the second caustic ring of dark matter in our galaxy. Caustic rings of dark matter were predicted in the…

Astrophysics · Physics 2007-05-23 Pierre Sikivie