Stellar streams as gravitational experiments

Thomas, Guillaume; Famaey, Benoît; Ibata, Rodrigo; Renaud, Florent; Martín, Nicolás F.; Kroupa, Pavel

doi:10.1051/0004-6361/201731609

Cited by 48 publications

(47 citation statements)

References 119 publications

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“…The cluster thus develops a thin leading tidal tail closer to the Galactic centre and a thin trailing tidal tail farther away. The tails are expected to compose a symmetric structure around the cluster (Thomas et al 2018). While the stars initially drift away from the cluster potential, they later partially and repeatedly return as tidal-tail stars, and their cluster of origin moves on orbits with slightly different eccentricities and consequently with different orbital frequencies.…”

Section: Introductionmentioning

confidence: 99%

The 800 pc long tidal tails of the Hyades star cluster

Jeřabková

Boffin

Beccari

et al. 2021

A&A

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The tidal tails of stellar clusters provide an important tool for studying the birth conditions of the clusters and their evolution, coupling, and interaction with the Galactic potential. The Gaia satellite, with its high-quality astrometric data, opened this field of study, allowing us to observe large-scale tidal tails. Theoretical models of tidal-tail formation and evolution are available. However, the exact appearance of tidal features as seen in the Gaia catalogue has not yet been studied. Here we present the N-body evolution of a Hyades-like stellar cluster with backward-integrated initial conditions on a realistic 3D orbit in the Milky Way galaxy computed within the AMUSE framework. For the first time, we explore the effect of the initial cluster rotation and the presence of lumps in the Galactic potential on the formation and evolution of tidal tails. For all of our simulations we present Gaia observables and derived parameters in the convergent point (CP) diagram. We show that the tidal tails are not naturally clustered in any coordinate system and that they can span up to 40 km s−1 relative to the cluster centre in proper motions for a cluster age of 600–700 Myr. Models with initial rotation result in significant differences in the cluster mass loss and follow different angular momentum time evolution. Thus the orientation of the tidal tails relative to the motion vector of the cluster and the current cluster angular momentum constrain the initial rotation of the cluster. We highlight the use of the standard CP method in searches for co-moving groups and introduce a new compact CP (CCP) method that accounts for internal kinematics based on an assumed model. Using the CCP method, we are able to recover candidate members of the Hyades tidal tails in the Gaia Data Release 2 and early Data Release 3 (eDR3) reaching a total extent of almost 1 kpc. We confirm the previously noted asymmetry in the detected tidal tails. In the eDR3 data we recovered spatial overdensities in the leading and trailing tails that are kinematically consistent with being epicyclic overdensities and thus would present candidates for the first such detection in an open star cluster. We show that the epicyclic overdensities are able to provide constraints not only on the cluster properties, but also on the Galactic potential. Finally, based on N-body simulations, a close encounter with a massive Galactic lump can explain the observed asymmetry in the tidal tails of the Hyades.

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Section: Introductionmentioning

confidence: 99%

The 800 pc long tidal tails of the Hyades star cluster

Jeřabková

Boffin

Beccari

et al. 2021

A&A

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“…Previous applications of POR to state-of-the art problems are available in the very-high-resolution simulations of Antennae-like galaxies (Renaud et al 2016), and (without hydro) in the simulation of the Sagittarius satellite galaxy and its stream by Thomas et al (2017) as well as the computations of streams from globular clusters (Thomas et al 2018), and the computation of the Andromeda-Milky-Way encounter by Bílek et al (2018). Prior to this, Milgromian simulations with gas (Tiret & Combes 2008;Combes 2014) were carried out by using sticky particles and a MOND Poisson solver (Brada & Milgrom 1999;Tiret & Combes 2007).…”

Section: Introductionmentioning

confidence: 99%

The Formation of Exponential Disk Galaxies in MOND

Wittenburg

Kroupa

Famaey

2020

ApJ

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The formation and evolution of galaxies is highly dependent on the dynamics of stars and gas, which is governed by the underlying law of gravity. To investigate how the formation and evolution of galaxies takes place in Milgromian gravity (MOND), we present full hydrodynamical simulations with the Phantom of Ramses (POR) code. These are the first-ever galaxy formation simulations done in MOND with detailed hydrodynamics, including star formation, stellar feedback, radiative transfer and supernovae. These models start from simplified initial conditions, in the form of isolated, rotating gas spheres in the early Universe. These collapse and form late-type galaxies obeying several scaling relations, which was not a priori expected. The formed galaxies have a compact bulge and a disk with exponentially decreasing surface mass density profiles and scale lengths consistent with observed galaxies, and vertical stellar mass distributions with distinct exponential profiles (thin and thick disk). This work thus shows for the first time that disk galaxies with exponential profiles in both gas and stars are a generic outcome of collapsing gas clouds in MOND. These models have a slight lack of stellar angular momentum because of their somewhat compact stellar bulge, which is connected to the simple initial conditions and the negligible later gas accretion. We also analyse how the addition of more complex baryonic physics changes the main resulting properties of the models and find this to be negligibly so in the Milgromian framework.

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“…When the external field dominates over the internal one, the amplitude of the MOND effect, and the corresponding amount of dark matter inferred, is reduced. Some interesting effects unique to MOND are related to the EFE, such as the prediction of asymmetric tidal streams of globular clusters (Thomas et al 2018).…”

Section: Introductionmentioning

confidence: 99%

MOND and the dynamics of NGC 1052−DF2

Famaey

McGaugh

Milgrom

2018

Monthly Notices of the Royal Astronomical Society

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The dwarf galaxy NGC1052-DF2 has recently been identified as potentially lacking dark matter. If correct, this could be a challenge for MOND, which predicts that low surface brightness galaxies should evince large mass discrepancies. However, the correct prediction of MOND depends on both the internal field of the dwarf and the external field caused by its proximity to the giant elliptical NGC1052. Taking both into consideration under plausible assumptions, we find σ MOND = 13.4 +4.8 −3.7 km s −1. This is only marginally higher than the claimed 90% upper limit on the velocity dispersion (σ < 10.5 km s −1), and compares well with the observed root mean square velocity dispersion (σ = 14.3 km s −1). We also discuss a few caveats on both the observational and theoretical side. On the theory side, the internal virialization time in this dwarf may be longer that the time scale of variation of the external field. On the observational side, the paucity of data and their large uncertainties call for further analysis of the velocity dispersion of NGC1052-DF2, to check whether it poses a challenge to MOND or is a success thereof.

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Stellar streams as gravitational experiments

Cited by 48 publications

References 119 publications

The 800 pc long tidal tails of the Hyades star cluster

The 800 pc long tidal tails of the Hyades star cluster

The Formation of Exponential Disk Galaxies in MOND

MOND and the dynamics of NGC 1052−DF2

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