The Phantom of RAMSES user guide for galaxy simulations using Milgromian and Newtonian gravity

Togere, Nagesh, Srikanth; Banik, Indranil; Thies, Ingo; Kroupa, Pavel; Famaey, Benoît; Wittenburg, Nils; Haslbauer, Moritz

doi:10.1139/cjp-2020-0624

Cited by 18 publications

(28 citation statements)

References 40 publications

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“…Banik et al (2020) provides further details regarding por and its application to thin disc galaxies, including links to download the algorithms used to prepare the initial conditions for both hydrodynamical and stellaronly thin disc simulations (Section 3.3.1). A user guide for por simulations has recently been published, including details on how to initialize isolated or interacting disc galaxy simulations consisting of only stars or also including hydrodynamics (Nagesh et al 2021). The guide also describes the extraction of both particle and gas data into human-readable form.…”

Section: Mond Simulations With Phantom Of Ramsesmentioning

confidence: 99%

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Barred spiral galaxies in modified gravity theories

Roshan

Banik

Ghafourian

et al. 2021

Monthly Notices of the Royal Astronomical Society

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When bars form within galaxy formation simulations in the standard cosmological context, dynamical friction with dark matter (DM) causes them to rotate rather slowly. However, almost all observed galactic bars are fast in terms of the ratio between corotation radius and bar length. Here, we explicitly display an 8σ tension between the observed distribution of this ratio and that in the EAGLE simulation at redshift 0. We also compare the evolution of Newtonian galactic discs embedded in DM haloes to their evolution in three extended gravity theories: Milgromian Dynamics (MOND), a model of non-local gravity, and a scalar-tensor-vector gravity theory (MOG). Although our models start with the same initial baryonic distribution and rotation curve, the long-term evolution is different. The bar instability happens more violently in MOND compared to the other models. There are some common features between the extended gravity models, in particular the negligible role played by dynamical friction − which plays a key role in the DM model. Partly for this reason, all extended gravity models predict weaker bars and faster bar pattern speeds compared to the DM case. Although the absence of strong bars in our idealized, isolated extended gravity simulations is in tension with observations, they reproduce the strong observational preference for ‘fast’ bar pattern speeds, which we could not do with DM. We confirm previous findings that apparently ‘ultrafast’ bars can be due to bar-spiral arm alignment leading to an overestimated bar length, especially in extended gravity scenarios where the bar is already fast.

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Section: Mond Simulations With Phantom Of Ramsesmentioning

confidence: 99%

“…Algorithms used to run the MOND simulations and extract data from them are discussed further in Banik et al (2020), which also contains links to download the algorithms. Installation and operating instructions are described in Nagesh et al (2021).…”

Section: Data Availabilitymentioning

confidence: 99%

Barred spiral galaxies in modified gravity theories

Roshan

Banik

Ghafourian

et al. 2021

Monthly Notices of the Royal Astronomical Society

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“…A similar algorithm called raymond has been developed to handle both the AQUAL and QUMOND formulations of MOND (Candlish et al 2015), also by adapting ramses. For a user manual on how to conduct N -body and hydrodynamical simulations in QUMOND with por, we refer the reader to Nagesh et al (2021), which briefly reviews all numerical MOND simulations and codes prior to its publication and also explains how to initialize isolated and interacting disc galaxy models (the disc templates are discussed further in Banik et al 2020).…”

Section: Numerical Solversmentioning

confidence: 99%

“…In some models, this aligned with the observed satellite plane orbital pole for both the MW and M31 (see their figure 5). This work is currently being followed up with hydrodynamical simulations in por of a flyby between two disc galaxies, which were set up using procedures similar to those described in Nagesh et al (2021). Preliminary results (I.…”

Section: The Local Group Satellite Planesmentioning

confidence: 99%

From galactic bars to the Hubble tension: weighing up the astrophysical evidence for Milgromian gravity

Banik,

Zhao

2021

Preprint

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Astronomical observations reveal a major deficiency in our understanding of physics − the detectable mass is insufficient to explain the observed motions in a huge variety of systems given our current understanding of gravity, Einstein's General theory of Relativity (GR). This missing gravity problem may indicate a breakdown of GR at low accelerations, as posited by Milgromian dynamics (MOND). We review the MOND theory and its consequences, including in a cosmological context where we advocate a hybrid approach involving light sterile neutrinos to address MOND's cluster-scale issues. We then test the novel predictions of MOND using evidence from galaxies, galaxy groups, galaxy clusters, and the large scale structure of the Universe. We also consider whether the standard cosmological paradigm (ΛCDM) can explain the observations, and review several previously published highly significant falsifications of it. Our overall assessment considers both the extent to which the data agree with each theory and how much flexibility each has when accommodating the data, with the gold standard being a clear a priori prediction not informed by the data in question. We also consider some future tests, including on scales much smaller than galaxies. Our conclusion is that MOND is favoured by a wealth of data across a huge range of astrophysical scales, ranging from the kpc scales of galactic bars to the Gpc scale of the local supervoid and the Hubble tension, which is alleviated in MOND through enhanced cosmic variance.

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“…We decided for QUMOND for our simulation because of publicly available software that is suitable for simulations of galaxy interactions and can work in QUMOND. It is the Phantom of RAMSES code, or PoR 1 [87,88], that is based on the popular adaptive mesh refinement code RAMSES [89].…”

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confidence: 99%

Are Disks of Satellites Comprised of Tidal Dwarf Galaxies?

et al. 2021

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It was found that satellites of nearby galaxies can form flattened co-rotating structures called disks of satellites or planes of satellites. Their existence is not expected by the current galaxy formation simulations in the standard dark matter-based cosmology. On the contrary, modified gravity offers a promising alternative: the objects in the disks of satellites are tidal dwarf galaxies, that is, small galaxies that form from tidal tails of interacting galaxies. After introducing the topic, we review here our work on simulating the formation of the disks of satellites of the Milky Way and Andromeda galaxies. The initial conditions of the simulation were tuned to reproduce the observed positions, velocities and disk orientations of the galaxies. The simulation showed that the galaxies had a close flyby 6.8 Gyr ago. One of the tidal tails produced by the Milky Way was captured by Andromeda. It formed a cloud of particles resembling the disk of satellites at Andromeda by its size, orientation, rotation and mass. A hint of a disk of satellites was formed at the Milky Way too. In addition, the encounter induced a warp in the disk of the simulated Milky Way that resembles the real warp by its magnitude and orientation. We present here, for the first time, the proper motions of the members of the disk of satellites of Andromeda predicted by our simulation. Finally, we point out some of the remaining open questions which this hypothesis, for the formation of disks of satellites, brings up.

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The Phantom of RAMSES user guide for galaxy simulations using Milgromian and Newtonian gravity

Cited by 18 publications

References 40 publications

Barred spiral galaxies in modified gravity theories

Barred spiral galaxies in modified gravity theories

From galactic bars to the Hubble tension: weighing up the astrophysical evidence for Milgromian gravity

Are Disks of Satellites Comprised of Tidal Dwarf Galaxies?

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