scholarly journals The Clustering of Orbital Poles Induced by the LMC: Hints for the Origin of Planes of Satellites

2021 ◽  
Vol 923 (2) ◽  
pp. 140
Author(s):  
Nicolás Garavito-Camargo ◽  
Ekta Patel ◽  
Gurtina Besla ◽  
Adrian M. Price-Whelan ◽  
Facundo A. Gómez ◽  
...  
Keyword(s):  
Dark Matter ◽  
Milky Way ◽  
Random Distribution ◽  
Orbital Plane ◽  
Great Circle ◽  
Mass Ratio ◽  
Dynamical Friction ◽  
Physical Mechanisms ◽  
Collective Response ◽  
Sinusoidal Pattern

Abstract A significant fraction of Milky Way (MW) satellites exhibit phase-space properties consistent with a coherent orbital plane. Using tailored N-body simulations of a spherical MW halo that recently captured a massive (1.8 × 1011 M ⊙) LMC-like satellite, we identify the physical mechanisms that may enhance the clustering of orbital poles of objects orbiting the MW. The LMC deviates the orbital poles of MW dark matter particles from the present-day random distribution. Instead, the orbital poles of particles beyond R ≈ 50 kpc cluster near the present-day orbital pole of the LMC along a sinusoidal pattern across the sky. The density of orbital poles is enhanced near the LMC by a factor δ ρ max = 30% (50%) with respect to underdense regions and δ ρ iso = 15% (30%) relative to the isolated MW simulation (no LMC) between 50 and 150 kpc (150–300 kpc). The clustering appears after the LMC’s pericenter (≈50 Myr ago, 49 kpc) and lasts for at least 1 Gyr. Clustering occurs because of three effects: (1) the LMC shifts the velocity and position of the central density of the MW’s halo and disk; (2) the dark matter dynamical friction wake and collective response induced by the LMC change the kinematics of particles; (3) observations of particles selected within spatial planes suffer from a bias, such that measuring orbital poles in a great circle in the sky enhances the probability of their orbital poles being clustered. This scenario should be ubiquitous in hosts that recently captured a massive satellite (at least ≈1:10 mass ratio), causing the clustering of orbital poles of halo tracers.

scholarly journals Exploring the connection between stellar halo profiles and accretion histories in L* galaxies

2016 ◽  
Vol 11 (S321) ◽  
pp. 90-92
Author(s):  
Nicola C. Amorisco
Keyword(s):  
Stochastic Process ◽  
Monte Carlo ◽  
Density Profile ◽  
Ex Situ ◽  
Mass Ratio ◽  
Dynamical Friction ◽  
Physical Mechanisms ◽  
Stellar Halo ◽  
Low Mass ◽  
Negative Gradient

AbstractI use a library of controlled minor merger N-body simulations, a particle tagging technique and Monte Carlo generated ΛCDM accretion histories to study the highly stochastic process of stellar deposition onto the accreted stellar halos (ASHs) of L* galaxies. I explore the main physical mechanisms that drive the connection between the accretion history and the density profile of the ASH. I find that: i) through dynamical friction, more massive satellites are more effective at delivering their stars deeper into the host; ii) as a consequence, ASHs feature a negative gradient between radius and the local mass-weighed virial satellite-to-host mass ratio; iii) in L* galaxies, most ASHs feature a density profile that steepens towards sharper logarithmic slopes at increasing radii, though with significant halo-to-halo scatter; iv) the ASHs with the largest total ex-situ mass are such because of the chance accretion of a small number of massive satellites (rather than of a large number of low-mass ones).

scholarly journals The twisted dark matter halo of the Milky Way

2020 ◽  
Author(s):  
Shi Shao ◽  
Marius Cautun ◽  
Alis Deason ◽  
Carlos S Frenk
Keyword(s):  
Dark Matter ◽  
Milky Way ◽  
Orbital Plane ◽  
Minor Axis ◽  
Dark Matter Halo ◽  
Misalignment Angle ◽  
Stellar Disc ◽  
Confidence Levels ◽  
The Common ◽  
Inner Parts

Abstract We analyse systems analogous to the Milky Way (MW) in the eagle cosmological hydrodynamics simulation in order to deduce the likely structure of the MW’s dark matter halo. We identify MW-mass haloes in the simulation whose satellite galaxies have similar kinematics and spatial distribution to those of the bright satellites of the MW, specifically systems in which the majority of the satellites (8 out of 11) have nearly co-planar orbits that are also perpendicular to the central stellar disc. We find that the normal to the common orbital plane of the co-planar satellites is well aligned with the minor axis of the host dark matter halo, with a median misalignment angle of only 17.3○. Based on this result, we infer that the minor axis of the Galactic dark matter halo points towards (l, b) = (182○, −2○), with an angular uncertainty at the 68 and 95 percentile confidence levels of 22○ and 43○ respectively. Thus, the inferred minor axis of the MW halo lies in the plane of the stellar disc. The halo, however, is not homologous and its flattening and orientation vary with radius. The inner parts of the halo are rounder than the outer parts and well aligned with the stellar disc (that is the minor axis of the halo is perpendicular to the disc). Further out, the halo twists and the minor axis changes direction by 90○. This twist occurs over a very narrow radial range and reflects variations in the filamentary network along which mass was accreted into the MW.

scholarly journals Radial migration and vertical action in N-body simulations

2020 ◽  
Vol 495 (3) ◽  
pp. 3295-3306
Author(s):  
Daniel Mikkola ◽  
Paul J McMillan ◽  
David Hobbs
Keyword(s):  
Dark Matter ◽  
Structural Properties ◽  
Milky Way ◽  
Dark Matter Halo ◽  
Mass Ratio ◽  
Spiral Arms ◽  
Radial Migration ◽  
Vertical Action ◽  
Disc Galaxies ◽  
Radial Action

ABSTRACT We study the radial migration of stars as a function of orbital action as well as the structural properties of a large suite of N-body simulations of isolated disc galaxies. Our goal is to establish a relationship between the radial migration efficiency of stars and their vertical action. We aim to describe how that relationship depends on the relative gravitational dominance between the disc and the dark matter halo. By changing the mass ratio of our disc and dark matter halo, we find a relationship between disc dominance, number, and strength of spiral arms, and the ensuing radial migration as a function of the vertical action. We conclude that the importance of migration at large vertical action depends on the strength of the spiral arms and therefore the dominance of the disc. Populations with more radial action undergo less radial migration, independently of disc dominance. Our results are important for the future of analytical modelling of radial migration in galaxies and further the understanding of radial migration that is a key component of the restructuring of galaxies, including the Milky Way.

scholarly journals The impact of inelastic self-interacting dark matter on the dark matter structure of a Milky Way halo

2020 ◽  
Author(s):  
Kun Ting Eddie Chua ◽  
Karia Dibert ◽  
Mark Vogelsberger ◽  
Jesús Zavala
Keyword(s):  
Dark Matter ◽  
High Speed ◽  
Cold Dark Matter ◽  
Milky Way ◽  
Direct Detection ◽  
Major Axis ◽  
Inelastic Collisions ◽  
Axis Ratio ◽  
Lower Velocity ◽  
The Impact

Abstract We study the effects of inelastic dark matter self-interactions on the internal structure of a simulated Milky Way (MW)-size halo. Self-interacting dark matter (SIDM) is an alternative to collisionless cold dark matter (CDM) which offers a unique solution to the problems encountered with CDM on sub-galactic scales. Although previous SIDM simulations have mainly considered elastic collisions, theoretical considerations motivate the existence of multi-state dark matter where transitions from the excited to the ground state are exothermic. In this work, we consider a self-interacting, two-state dark matter model with inelastic collisions, implemented in the Arepo code. We find that energy injection from inelastic self-interactions reduces the central density of the MW halo in a shorter timescale relative to the elastic scale, resulting in a larger core size. Inelastic collisions also isotropize the orbits, resulting in an overall lower velocity anisotropy for the inelastic MW halo. In the inner halo, the inelastic SIDM case (minor-to-major axis ratio s ≡ c/a ≈ 0.65) is more spherical than the CDM (s ≈ 0.4), but less spherical than the elastic SIDM case (s ≈ 0.75). The speed distribution f(v) of dark matter particles at the location of the Sun in the inelastic SIDM model shows a significant departure from the CDM model, with f(v) falling more steeply at high speeds. In addition, the velocity kicks imparted during inelastic collisions produce unbound high-speed particles with velocities up to 500 km s−1 throughout the halo. This implies that inelastic SIDM can potentially leave distinct signatures in direct detection experiments, relative to elastic SIDM and CDM.

scholarly journals The Large Range of Dark Matter content in Dwarf Galaxies and its Implications

1996 ◽  
Vol 171 ◽  
pp. 435-435
Author(s):  
S.A. Pustilnik ◽  
V.A. Lipovetsky ◽  
J.-M. Martin ◽  
T.X. Thuan
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Large Range ◽  
Dwarf Galaxy ◽  
Rotational Velocity ◽  
Matter Content ◽  
Optical Observations ◽  
Strong Interactions ◽  
Formation Mechanisms ◽  
Mass Ratio

We present the analysis of a new set of radio and optical observations of a large sample of Byurakan Blue Compact Galaxies. HI spectra were obtained with the Nançay 300-m and Green Bank 43-m radio telescopes. CCD-images were taken with the KPNO 0.9-m and Whipple Observatory 1.2-m telescopes. Dark Matter (DM) to luminous mass ratios in these BCGs were found to vary from about less than 0.5 up to 14. Recent data taken from the literature indicate this same range. This result has important consequences on models of dwarf galaxy formation, indicating possibly different formation mechanisms. The standard CDM model of dwarfs formation requires large DM halos. However the formation of dwarfs as tidal debris resulting from strong interactions of massive spirals leads naturally to dwarfs with low content of DM. On Fig.1 we show DM to luminous mass ratio versus rotational velocity for our BCGs and some other galaxies.

scholarly journals CONSTRAINTS ON THE SHAPE OF THE MILKY WAY DARK MATTER HALO FROM JEANS EQUATIONS APPLIED TO SLOAN DIGITAL SKY SURVEY DATA

2012 ◽  
Vol 758 (1) ◽  
pp. L23 ◽  
Author(s):  
Sarah R. Loebman ◽  
Željko Ivezić ◽  
Thomas R. Quinn ◽  
Fabio Governato ◽  
Alyson M. Brooks ◽  
...  
Keyword(s):  
Dark Matter ◽  
Survey Data ◽  
Milky Way ◽  
Sloan Digital Sky Survey ◽  
Dark Matter Halo ◽  
Sky Survey

scholarly journals Testing dark matter and modifications to gravity using local Milky Way observables

2019 ◽  
Vol 100 (8) ◽  
Author(s):  
Mariangela Lisanti ◽  
Matthew Moschella ◽  
Nadav Joseph Outmezguine ◽  
Oren Slone
Keyword(s):  
Dark Matter ◽  
Milky Way

scholarly journals Dark Matter: An Efficient Catalyst for Intermediate-mass-ratio-inspiral Events

2019 ◽  
Vol 874 (1) ◽  
pp. 34 ◽  
Author(s):  
Xiao-Jun Yue ◽  
Wen-Biao Han ◽  
Xian Chen
Keyword(s):  
Dark Matter ◽  
Mass Ratio ◽  
Intermediate Mass ◽  
Efficient Catalyst

scholarly journals Probing non-spherical dark halos in the Galactic dwarf satellites

2013 ◽  
Vol 9 (S298) ◽  
pp. 411-411
Author(s):  
Kohei Hayashi ◽  
Masashi Chiba
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
Milky Way ◽  
Velocity Dispersion ◽  
Line Of Sight ◽  
Spherical Structure ◽  
Spherical Models ◽  
Galactic Satellites ◽  
Best Fitting

AbstractWe construct axisymmetric mass models for dwarf spheroidal (dSph) galaxies in the Milky Way to obtain realistic limits on the non-spherical structure of their dark halos. This is motivated by the fact that the observed luminous parts of the dSphs are actually non-spherical and cold dark matter models predict non-spherical virialized dark halos on sub-galactic scales. Applying these models to line-of-sight velocity dispersion profiles along three position angles in six Galactic satellites, we find that the best fitting cases for most of the dSphs yield not spherical but oblate and flattened dark halos. We also find that the mass of the dSphs enclosed within inner 300 pc varies depending on their total luminosities, contrary to the conclusion of previous spherical models. This suggests the importance of considering non-spherical shapes of dark halos in dSph mass models.

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