The unexpected diversity of dwarf galaxy rotation curves

Oman, Kyle A.; Navarro, Julio F.; Fattahi, Azadeh; Frenk, Carlos S.; Sawala, Till; White, Simon D. M.; Bower, Richard; Crain, Robert A.; Furlong, Michelle; Schaller, Matthieu; Schaye, Joop; Theuns, Tom

doi:10.1093/mnras/stv1504

Cited by 426 publications

(500 citation statements)

References 76 publications

(143 reference statements)

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“…Since ν depends on gN, it also scales with the baryonic surface density, and a prediction of MOND is consequently that the central circular velocity slope depends mainly on the central baryonic surface density of the galaxy. Hence, MOND naturally predicts the diversity of rotation curve shapes at a given mass scale noted by Oman et al (2015), solely from the existence, at a given mass scale, of a diversity of central baryonic surface densities, and it also predicts a strong correlation of the latter with the circular velocity gradient ( dV / dR)0, as observed by Lelli et al (2013). Outside of spherical symmetry, the previous formula must nevertheless be modified.…”

Section: Modified Gravitymentioning

confidence: 93%

Star formation triggered by galaxy interactions in modified gravity

Famaey¹,

Kroupa²

2016

Mon. Not. R. Astron. Soc.

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Together with interstellar turbulence, gravitation is one key player in star formation. It acts both at galactic scales in the assembly of gas into dense clouds, and inside those structures for their collapse and the formation of pre-stellar cores. To understand to what extent the large scale dynamics govern the star formation activity of galaxies, we present hydrodynamical simulations in which we generalise the behaviour of gravity to make it differ from Newtonian dynamics in the low acceleration regime. We focus on the extreme cases of interacting galaxies, and compare the evolution of galaxy pairs in the dark matter paradigm to that in the Milgromian Dynamics (MOND) framework. Following up on the seminal work by Tiret & Combes, this paper documents the first simulations of galaxy encounters in MOND with a detailed Eulerian hydrodynamical treatment of baryonic physics, including star formation and stellar feedback. We show that similar morphologies of the interacting systems can be produced by both the dark matter and MOND formalisms, but require a much slower orbital velocity in the MOND case. Furthermore, we find that the star formation activity and history are significantly more extended in space and time in MOND interactions, in particular in the tidal debris. Such differences could be used as observational diagnostics and make interacting galaxies prime objects in the study of the nature of gravitation at galactic scales.

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Section: Modified Gravitymentioning

confidence: 93%

Star formation triggered by galaxy interactions in modified gravity

Famaey¹,

Kroupa²

2016

Mon. Not. R. Astron. Soc.

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“…Results from a subset of these simulations have already been presented in Sawala et al (2015Sawala et al ( , 2016 and Oman et al (2015). Here we describe the selection procedure for the resimulation volumes together with the physical processes included in the simulations.…”

Section: The a P O S T L E S I M U L At I O N Smentioning

confidence: 99%

“…The goal of this paper is to motivate the particular choices made for this selection whilst critically reviewing the constraints on the total mass of the LG placed by the kinematics of LG members. Preliminary results from the project (which we shall hereafter refer to as APOSTLE, a shorthand for 'A Project Of Simulating The Local Environment'), which uses the same code developed for the EAGLE simulations (Crain et al 2015;Schaye et al 2015), have already been reported in Sawala et al (2015Sawala et al ( , 2016 and Oman et al (2015).…”

mentioning

confidence: 99%

The apostle project: Local Group kinematic mass constraints and simulation candidate selection

Fattahi

Navarro

Sawala

et al. 2016

Mon. Not. R. Astron. Soc.

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268

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We use a large sample of isolated dark matter halo pairs drawn from cosmological N-body simulations to identify candidate systems whose kinematics match that of the Local Group of Galaxies (LG). We find, in agreement with the "timing argument" and earlier work, that the separation and approach velocity of the Milky Way (MW) and Andromeda (M31) galaxies favour a total mass for the pair of ∼ 5 × 10 12 M ⊙ . A mass this large, however, is difficult to reconcile with the small relative tangential velocity of the pair, as well as with the small deceleration from the Hubble flow observed for the most distant LG members. Halo pairs that match these three criteria have average masses a factor of ∼ 2 times smaller than suggested by the timing argument, but with large dispersion, spanning more than a decade in mass. Guided by these results, we have selected 12 halo pairs with total mass in the range 1.6-3.6 × 10 12 M ⊙ for the APOSTLE project (A Project Of Simulations of The Local Environment), a suite of resimulations at various numerical resolution levels (reaching up to ∼ 10 4 M ⊙ per gas particle) that use the hydrodynamical code and subgrid physics developed for the EA-GLE project. These simulations reproduce, by construction, the main kinematics of the MW-M31 pair, and produce satellite populations whose overall number, luminosities, and kinematics are in good agreement with observations of the MW and M31 companions. These diagnostics are sensitive to the total mass assumed for the MW-M31 pair; indeed, the LG satellite population would be quite difficult to reproduce for pair masses as high as indicated by the timing argument. The APOSTLE candidate systems thus provide an excellent testbed to confront directly many of the predictions of the ΛCDM cosmology with observations of our local Universe.

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“…In general, a strong variation is found from dwarf to dwarf, and in some cases like NGC4449 (Theis & Kohle 2001) or IC 10 (Ashley et al 2014, the rotation curves have been explained by tidal interactions of disks with other dwarfs. The implications of the large diversity of dwarf galaxy rotation curves has therefore been discussed also in recent studies (Oman et al 2015).…”

Section: Introductionmentioning

confidence: 96%

Star-forming dwarf galaxies: the correlation between far-infrared and radio fluxes

Schleicher

Beck

2016

A&A

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The far-infrared -radio correlation connects star formation and magnetic fields in galaxies, and has been confirmed over a large range of far-infrared / radio luminosities, both in the local Universe and even at redshifts of z ∼ 2. Recent investigations indicate that it may even hold in the regime of local dwarf galaxies, and we therefore explore here the expected behavior in the regime of star formation surface densities below 0.1 M⊙ kpc −2 yr −1 . We derive two conditions that can be particularly relevant for inducing a change in the expected correlation: a critical star formation surface density to maintain the correlation between star formation rate and the magnetic field, and a critical star formation surface density below which cosmic ray diffusion losses dominate over their injection via supernova explosions. For rotation periods shorter than 1.5 × 10 7 (H/kpc) 2 yrs, with H the scale height of the disk, the first correlation will break down before diffusion losses are relevant, as higher star formation rates are required to maintain the correlation between star formation rate and magnetic field strength. For high star formation surface densities ΣSFR, we derive a characteristic scaling of the non-thermal radio to the far-infrared / infrared emission with Σ 1/3 SFR , corresponding to a scaling of the non-thermal radio luminosity Ls with the infrared luminosity L th as L 4/3 th . The latter is expected to change when the above processes are no longer steadily maintained. In the regime of long rotation periods, we expect a transition towards a steeper scaling with Σ 2/3 SFR , implying Ls ∝ L 5/3th , while the regime of fast rotation is expected to show a considerably enhanced scatter, as a well-defined relation between star formation and magnetic field strength is not maintained. The scaling relations above explain the increasing thermal fraction of the radio emission observed within local dwarfs, and can be tested with future observations by LOFAR as well as the SKA and its precursor radio telescopes.

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The unexpected diversity of dwarf galaxy rotation curves

Cited by 426 publications

References 76 publications

Star formation triggered by galaxy interactions in modified gravity

Star formation triggered by galaxy interactions in modified gravity

The apostle project: Local Group kinematic mass constraints and simulation candidate selection

Star-forming dwarf galaxies: the correlation between far-infrared and radio fluxes

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