The Relevance of Dynamical Friction for the MW/LMC/SMC Triple System

Oehm, Wolfgang; Kroupa, Pavel

doi:10.3390/universe10030143

Cited by 4 publications

(3 citation statements)

References 72 publications

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“…Indeed, apart from the above and apart from the fact that dark matter particles have not been found experimentally despite 40 yr of search, tests for the existence of dark matter particles that had been hoped to be accounting for the apparent non-Newtonian phenomena on galaxy scales have been yielding negative results: the presence of dark matter halos has been significantly questioned by the properties of dwarf galaxies in the Fornax galaxy cluster (Asencio et al 2022). Applying the Chandrasekhar dynamical friction test to various galaxy systems (Kroupa 2015;Kroupa et al 2023), and most recently on the Milky-Way/Large-/Small-Magellanic-Cloud triple system (Oehm & Kroupa 2024), shows no orbital solutions to be possible as the systems merge too quickly to be consistent with their observed configuration in phase-space. Solutions without dark matter particles but with Milgromian potentials are readily obtained though.…”

Section: Discussionmentioning

confidence: 99%

Asymmetrical tidal tails of open star clusters: stars crossing their cluster’s práh† challenge Newtonian gravitation

Kroupa

Jeřabková

Thies

et al. 2022

Monthly Notices of the Royal Astronomical Society

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After their birth a significant fraction of all stars pass through the tidal threshold (práh) of their cluster of origin into the classical tidal tails. The asymmetry between the number of stars in the leading and trailing tails tests gravitational theory. All five open clusters with tail data (Hyades, Praesepe, Coma Berenices, COIN-Gaia 13, NGC 752) have visibly more stars within $d_{\rm cl}\approx 50\,{\rm pc}$ of their centre in their leading than their trailing tail. Using the Jerabkova-compact-convergent-point (CCP) method, the extended tails have been mapped out for four nearby 600–2000 Myr old open clusters to $d_{\rm cl} > 50\,{\rm pc}$. These are on near-circular Galactocentric orbits, a formula for estimating the orbital eccentricity of an open cluster being derived. Applying the Phantom of Ramses code to this problem in Newtonian gravitation the tails are near-symmetrical. In Milgromian dynamics (MOND), the asymmetry reaches the observed values for 50 < dcl/pc < 200 being maximal near peri-galacticon, and can slightly invert near apo-galacticon, and the Küpper epicyclic overdensities are asymmetrically spaced. Clusters on circular orbits develop orbital eccentricity due to the asymmetrical spill-out, therewith spinning up opposite to their orbital angular momentum. This positive dynamical feedback suggests Milgromian open clusters to demise rapidly as their orbital eccentricity keeps increasing. Future work is necessary to better delineate the tidal tails around open clusters of different ages and to develop a Milgromian direct n-body code.

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Section: Discussionmentioning

confidence: 99%

Asymmetrical tidal tails of open star clusters: stars crossing their cluster’s práh† challenge Newtonian gravitation

Kroupa

Jeřabková

Thies

et al. 2022

Monthly Notices of the Royal Astronomical Society

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“…Indeed, apart from the above and apart from the fact that dark matter particles have not been found experimentally despite 40 yr of search, tests for the existence of dark matter particles that had been hoped to be accounting for the apparent non-Newtonian phenomena on galaxy scales have been yielding negative results: the presence of dark matter halos has been significantly questioned by the properties of dwarf galaxies in the Fornax galaxy cluster (Asencio et al 2022). Applying the Chandrasekhar dynamical friction test to various galaxy systems (Kroupa 2015;Kroupa et al 2023), and most recently to the triple system of the Milky Way and Large and Small Magellanic Clouds (Oehm & Kroupa 2024), shows no orbital solutions to be possible because the systems merge too quickly to be consistent with their observed configuration in phase space. Solutions without dark matter particles but with Milgromian potentials are readily obtained though.…”

Section: Discussionmentioning

confidence: 99%

Open Star Clusters and Their Asymmetrical Tidal Tails

Kroupa,

Pflamm-Altenburg,

Mazurenko

et al. 2024

ApJ

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Stars that evaporate from their star cluster by the energy equipartition process end up in either a leading or a trailing tidal tail. In Newtonian gravitation and for open star clusters in the solar vicinity, the tidal threshold, or práh, for escape is symmetrical, such that the leading and trailing tails are equally populated. The data from six independent teams that applied the convergent point method to map out the tidal tails of four open clusters (the Hyades, Praesepe, Coma Berenices, and COIN-Gaia 13) using Gaia DR2 and DR3 are here applied to test for the expected symmetry. All tidal tails contain more stars in the leading tail. The combined confidence amounts to an 8σ falsification of the práh symmetry. The same test using Milgromian dynamics leads to consistency with the data. More effort needs to be exerted on this matter, but the data indicate with high confidence that the tidal práh of an open star cluster is asymmetrical, with the corresponding confidence that Newtonian gravitation is falsified. Open star clusters depopulate more rapidly in Milgromian than in Newtonian dynamics, and the COIN-Gaia 13 cluster is here found to be nearly completely dissolved. In view of these results, the wide-binary star test and the finding of a Keplerian Galactic rotation curve are briefly discussed.

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“…The dark matter (DM) problem is still an outstanding riddle, but various aspects challenge ΛCDM: absence of dynamical friction in galaxy merging (Kroupa, 2015;Oehm and Kroupa, 2024) and in galactic bars (Roshan et al, 2021); as per MOND, structures in the baryons correspond to structures in the rotation velocity. The Hubble tension expresses the difference between the Hubble constant H 0 ≈ 68 km/s Gpc from the cosmic microwave radiation (Aghanim et al, 2020) versus the 73 km/s Gpc from supernovae in the nearby Universe (Brout et al, 2022).…”

Section: Present Statusmentioning

confidence: 99%

Solution of the dark matter riddle within standard model physics: from black holes, galaxies and clusters to cosmology

Nieuwenhuizen

2024

Front. Astron. Space Sci.

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It is postulated that the energy density of the (quantum) vacuum acts firstly as dark energy and secondly as a part of dark matter. Assisted by electric fields arising from a small charge mismatch in the cosmic plasma, it can condense on mass concentrations. No longer participating in the cosmic expansion, this constitutes “electro-aether-energy” (EAE), “electro-zero-point-energy” or “electro-vacuum-energy”, which solves the dark matter riddle without new physics. A radial electric field of 1 kV/m is predicted in the Galaxy. For proper electric fields, EAE can cover the results deduced with MOND. An instability allows a speedy filling of dark matter cores. Hydrostatic equilibrium in galaxy clusters is obeyed. Flowing in aether energy of explains why black holes become supermassive, do not have mass gaps and overcome the final parsec problem. Rupture of charged clouds reduces, e.g., the primordial baryon cloud to the cosmic web. The large coherence scale of the electric field acts as a scaffold for gentle galaxy formation and their vast polar structures. In galaxy merging and bars, there occurs no dynamical friction. At cosmological scales, EAE acts as pressureless dark matter. Its amount increases in time, which likely solves the Hubble tension by its late time physics. A big crunch can occur. Of the large cosmological constant injected at the Big Bang, a small part kept that form, without fine-tuning.

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The Relevance of Dynamical Friction for the MW/LMC/SMC Triple System

Cited by 4 publications

References 72 publications

Asymmetrical tidal tails of open star clusters: stars crossing their cluster’s práh† challenge Newtonian gravitation

Asymmetrical tidal tails of open star clusters: stars crossing their cluster’s práh† challenge Newtonian gravitation

Open Star Clusters and Their Asymmetrical Tidal Tails

Solution of the dark matter riddle within standard model physics: from black holes, galaxies and clusters to cosmology

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