Star formation triggered by galaxy interactions in modified gravity

Famaey, Benoît; Kroupa, Pavel

doi:10.1093/mnras/stw2331

Cited by 58 publications

(78 citation statements)

References 105 publications

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“…Galaxy encounters in generalised gravity models (e.g. Renaud et al 2016) should be rarer and not all of these should lead to mergers, since an absence of dark matter leads to a lesser amount of dynamical friction, allowing for a larger number of hyperbolic flybys. As a consequence, there may be more major galaxies with masses similar to the Milky Way, which do not show a bulge at all, consistent with observations (Fisher & Drory 2011;Kroupa 2015) and with the gradual decrease of the fraction of bulgeless sources in the full sample of disk galaxies during the last ≈7.5 × 10 9 yr (Sachdeva 2013).…”

Section: Motivationmentioning

confidence: 99%

DGSAT: Dwarf Galaxy Survey with Amateur Telescopes

Henkel

Javanmardi

Martínez–Delgado

et al. 2017

A&A

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The connection between the bulge mass or bulge luminosity in disk galaxies and the number, spatial and phase space distribution of associated dwarf galaxies is a discriminator between cosmological simulations related to galaxy formation in cold dark matter and generalised gravity models. Here, a nearby sample of isolated Milky Wayclass edge-on galaxies is introduced, to facilitate observational campaigns to detect the associated families of dwarf galaxies at low surface brightness. Three galaxy pairs with at least one of the targets being edge-on are also introduced. Approximately 60% of the catalogued isolated galaxies contain bulges of different size, while the remaining objects An edge-on sample of nearby galaxies a surface brightness of µr ≈ 26 mag arcsec −2 and effective radius >1.5 kpc to the class of ultra-diffuse galaxies (UDGs). NGC 3669-DGSAT-3, the galaxy with the lowest surface brightness in our sample, may also be an UDG.

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Section: Motivationmentioning

confidence: 99%

DGSAT: Dwarf Galaxy Survey with Amateur Telescopes

Henkel

Javanmardi

Martínez–Delgado

et al. 2017

A&A

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“…When integrated backwards, the orbits of the Large and Small Magellanic Clouds were close to pericenter almost when the MW and M 31 were at the pericenter. Dynamical friction during encounters of comparable galaxies is known to be weaker in MOND than in ΛCDM from the simulations by ; Nipoti et al (2008); Combes (2016) (see also, Renaud et al 2016or Vakili et al 2017 because of the absence of the large and massive dark matter halos (Kroupa 2015). A close MW-M 31 encounter in MOND would therefore be more likely to avoid ending in a merger than in ΛCDM.…”

Section: Introductionmentioning

confidence: 96%

MOND simulation suggests an origin for some peculiarities in the Local Group

Bílek

Thies

Kroupa

et al. 2018

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Context. The Milky Way (MW) and Andromeda (M 31) galaxies possess rotating planes of satellites. Their formation has not been explained satisfactorily yet. It was suggested that the MW and M 31 satellites are ancient tidal dwarf galaxies, which could explain their configuration. This suggestion gained support by an analytic backward calculation of the relative MW-M 31 orbit in the MOND modified dynamics paradigm by Zhao et al. (2013) implying their close flyby 7-11 Gyr ago. Aims. Here we explore the Local Group history in MOND in more detail using a simplified first-ever self-consistent simulation. We note the features induced by the encounter in the simulation and identify their possible real counterparts. Methods. The initial conditions were set to eventually roughly reproduce the observed MW and M 31 masses, effective radii, separation, relative velocity and disk inclinations. We used the publicly available adaptive-mesh-refinement code Phantom of RAMSES. Results. Matter was transferred from the MW to M 31 along a tidal tail in the simulation. The encounter induced formation of several structures resembling the peculiarities of the Local Group. Most notably: 1) A rotating planar structure formed around M 31 from the transferred material. It had a size similar to the observed satellite plane and was oriented edge-on to the simulated MW, just as the real one. 2) The same structure also resembled the tidal features observed around M 31 by its size and morphology. 3) A warp in the MW developed with an amplitude and orientation similar to that observed. 4) A cloud of particles formed around the simulated MW, with the extent of the actual MW satellite system. The encounter did not end by merging in a Hubble time. The simulated stellar disks also thickened as a result of the encounter. Conclusions. The simulation demonstrated that MOND can possibly explain many peculiarities of the Local Group, which should be verified by future more elaborate simulations. The simulation moreover showed that tidal features observed in galaxies, usually interpreted as merger remnants, could have been formed by matter exchange during non-merging galactic flybys in some cases.

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“…This has recently changed thanks, notably, to the recent generalizations of the Ramses code (Teyssier 2002;Lüghausen et al 2015;Candlish et al 2015). The version we use hereafter and in previous work (e.g., Renaud et al 2016; Thomas et al 2017), was developed by Lüghausen et al (2015).…”

Section: Introductionmentioning

confidence: 99%

Stellar streams as gravitational experiments

Thomas

Famaey

Ibata

et al. 2018

A&A

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Kinematically cold tidal streams of globular clusters (GC) are excellent tracers of the Galactic gravitational potential at moderate Galactocentric distances, and can also be used as probes of the law of gravity on Galactic scales. Here, we compare for the first time the generation of such streams in Newtonian and Milgromian gravity (MOND). We first compute analytical results to investigate the expected shape of the GC gravitational potential in both frameworks, and we then run N-body simulations with the Phantom of Ramses code. We find that the GCs tend to become lopsided in MOND. This is a consequence of the external field effect which breaks the strong equivalence principle. When the GC is filling its tidal radius the lopsidedness generates a strongly asymmetric tidal stream. In Newtonian dynamics, such markedly asymmetric streams can in general only be the consequence of interactions with dark matter subhalos, giant molecular clouds, or interaction with the Galactic bar. In these Newtonian cases, the asymmetry is the consequence of a very large gap in the stream, whilst in MOND it is a true asymmetry. This should thus allow us in the future to distinguish these different scenarios by making deep observations of the environment of the asymmetric stellar stream of Palomar 5. Moreover, our simulations indicate that the high internal velocity dispersion of Palomar 5 for its small stellar mass would be natural in MOND.

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Star formation triggered by galaxy interactions in modified gravity

Cited by 58 publications

References 105 publications

DGSAT: Dwarf Galaxy Survey with Amateur Telescopes

DGSAT: Dwarf Galaxy Survey with Amateur Telescopes

MOND simulation suggests an origin for some peculiarities in the Local Group

Stellar streams as gravitational experiments

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