Detection of the LMC-induced sloshing of the Galactic halo

Erkal, Denis; Deason, Alis J.; Belokurov, Vasily; Xue, Xiang-Xiang; Koposov, S. E.; Bird, Sarah; Liu, Chao; Simion, Iulia T.; Yang, Chengqun; Zhang, Lan; Zhao, Gang

doi:10.1093/mnras/stab1828

Cited by 77 publications

(52 citation statements)

References 60 publications

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“…The LMC has just recently passed the pericentre of its orbit, likely for the first time (e.g., Besla et al 2007), and hence did not yet radialize: its present-day tangential velocity of 310 km s −1 (Gaia Collaboration 2021) at a distance of 50 kpc corresponds to a circularity η = 0.7, using a fiducial Milky Way potential model from McMillan (2017). However, it causes a significant displacement (reflex motion) of the Milky Way centre with respect to its outer parts (Gómez et al 2015;Petersen & Peñarrubia 2020, 2021Erkal et al 2021) and a distortion of its halo (Garavito-Camargo et al 2019Cunningham et al 2020).…”

Section: Introductionmentioning

confidence: 99%

Radialization of satellite orbits in galaxy mergers

Vasiliev,

Belokurov,

Evans

2021

Preprint

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We consider the orbital evolution of satellites in galaxy mergers, focusing on the evolution of eccentricity. Using a large suite of N -body simulations, we study a previously unexplored phenomenon of satellite orbital radialization, i.e., a profound increase in the eccentricity of satellite's orbit as it decays under dynamical friction. While radialization is detected in a variety of different setups, we find that it is most efficient in the cases of high satellite mass, not very steep host density profiles, and high initial eccentricity. To understand the origin of this phenomenon, we run additional simulations with various physical factors selectively turned off: satellite mass loss, reflex motion and distortion of the host, etc. We find that all these factors are important for radialization, since it does not occur for point-mass satellites or when the host potential is replaced with an unperturbed initial profile. The analysis of forces and torques acting on both galaxies confirms the major role of self-gravity of both host and satellite in the reduction of orbital angular momentum. The classical Chandrasekhar dynamical friction formula, which accounts only for the forces between the host and the satellite, but not for internal distortions of both galaxies, does not match the evolution of eccentricity observed in N -body simulations.

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Section: Introductionmentioning

confidence: 99%

Radialization of satellite orbits in galaxy mergers

Vasiliev,

Belokurov,

Evans

2021

Preprint

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“…its outskirts, a reflex motion which would create a dipole in the stellar velocity field. Tentative observational evidence for this reflex motion has been recently provided by Petersen & Peñarrubia (2021) and Erkal et al (2021). This reflex motion is expected to be accompanied by a local wake trailing behind the LMC (see, e.g., Garavito-Camargo et al 2019), a phenomenon also tentatively detected by Conroy et al (2021).…”

Section: Introductionmentioning

confidence: 83%

Constraining the Milky Way halo kinematics via its Linear Response to the Large Magellanic Cloud

Rozier,

Famaey,

Siebert

et al. 2022

Preprint

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We model the response of spherical, non-rotating Milky Way (MW) dark matter and stellar halos to the Large Magellanic Cloud (LMC) using the matrix method of linear response theory. Our computations reproduce the main features of the dark halo response from simulations. We show that these features can be well separated by a harmonic decomposition: the large scale over/underdensity in the halo (associated with its reflex motion) corresponds to the = 1 terms, and the local overdensity to the ≥ 2 multipoles. Moreover, the dark halo response is largely dominated by the first order 'forcing' term, with little influence from self-gravity. This makes it difficult to constrain the underlying velocity distribution of the dark halo using the observed response of the stellar halo, but it allows us to investigate the response of stellar halo models with various velocity anisotropies: a tangential (respectively radial) halo produces a shallower (respectively stronger) response. We also show that only the local wake is responsible for these variations, the reflex motion being solely dependent on the MW potential. Therefore, we identify the structure (orientation and winding) of the in-plane quadrupolar (m = 2) response as a potentially good probe of the stellar halo anisotropy. Finally, our method allows us to tentatively relate the wake strength and shape to resonant effects: the strong radial response could be associated with the inner Lindblad resonance, and the weak tangential one with corotation.

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“…The recent passage of a massive accreted satellite complicates the situation further due to the resonances induced in the central DM halo: large transient density and kinematic perturbations (Choi et al 2009) are produced, creating the classical 'conic' wake trailing the satellite (Chandrasekhar 1943) as well as a collective response to the system as a whole (Garavito-Camargo et al 2019) and leading to a temporary change in the concentration of the halo (Wang et al 2020). In fact, it has been recently demonstrated that the LMC induces a reflex motion in the disk/halo of the MW (Gómez et al 2015;Erkal et al 2021;Petersen & Peñarrubia 2021) and a large wake in the halo of the MW (Conroy et al 2021). While modelling the wake and the other homogeneities is beyond the scope of this paper, our work suggests that the errors caused by the use of these spherical parametric models for the potential rival the 30% uncertainty in the virial mass of the MW, and is thus an important source of error to consider.…”

Section: Summary and Discussionmentioning

confidence: 99%

Uncertainties associated with the backward integration of dwarf satellites using simple parametric potentials

D'Souza,

Bell

2022

Preprint

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In order to backward integrate the orbits of Milky Way (MW) dwarf galaxies, much effort has been invested in recent years to constrain their initial phase-space coordinates. Yet equally important are the assumptions on the potential that the dwarf galaxies experience over time, especially given the fact that the MW is currently accreting the Large Magellanic Cloud (LMC). In this work, using a dark matter-only zoom-in simulation, we test whether the use of common parametric forms of the potential is adequate to successfully backward integrate the orbits of the subhaloes from their present-day positions. We parametrise the recovered orbits and compare them with those from the simulations. We find that simple symmetric parametric forms of the potential fail to capture the complexities and the inhomogeneities of the true potential experienced by the subhaloes. More specifically, modelling a recent massive accretion like that of the LMC as a sum of two spherical parametric potentials leads to substantial errors in the recovered parameters of the orbits. These errors rival those caused due to a) a 30% uncertainty in the virial mass of the MW and b) not modelling the potential of the recently accreted massive satellite. Our work suggests that i) the uncertainties in the parameters of the recovered orbits of some MW dwarfs may be under-estimated and that ii) researchers should characterise the uncertainties inherent to their choice of integration techniques and assumptions of the potential against cosmological zoom-in simulations of the MW, which include a recently-accreted LMC.

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Detection of the LMC-induced sloshing of the Galactic halo

Cited by 77 publications

References 60 publications

Radialization of satellite orbits in galaxy mergers

Radialization of satellite orbits in galaxy mergers

Constraining the Milky Way halo kinematics via its Linear Response to the Large Magellanic Cloud

Uncertainties associated with the backward integration of dwarf satellites using simple parametric potentials

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