2026-04-17T20:40:46Zhttps://recercat.cat/oai/request

oai:recercat.cat:2445/2213882025-11-21T05:27:09Zcom_2072_1057col_2072_478904col_2072_478917

00925njm 22002777a 4500 dc Palau, Carles G. author Miralda Escudé, Jordi author 2025-06-04T18:31:47Z 2025-06-04T18:31:47Z 2023 2025-06-04T18:31:48Z We explore constraints on the Milky Way dark matter halo oblateness using three stellarstreamsfrom globular clusters NGC3201, M68, and Palomar 5. Previous constraints on the gravitational potential from dynamical equilibrium of stellar populations and distant Milky Way satellites are included. We model the dark halo as axisymmetric with axis ratio qh ρ and four additional free parameters of a two power-law density profile. The halo axis ratio, while barely constrained by the NGC3201 stream alone, is required to be close to spherical by the streams of Palomar 5 (qh ρ = 1.01 ± 0.09) and M68 (qh ρ = 1.14+0.21 −0.14), the latter allowing a more prolate shape. The three streams together are well fitted with a halo axis ratio qh ρ = 1.06 ± 0.06 and core radius ∼20 kpc. Our estimate of the halo shape agrees with previous studies using other observational data and is in tension with cosmological simulations, predicting that most spiral galaxies have oblate dark matter haloes with the short axis perpendicular to the disc. We discuss why the impact of the Magellanic Clouds tide is too small to change our conclusion on the halo axis ratio. We note that dynamical equilibrium of a spherical halo in the oblate disc potential implies an anisotropic dark matter velocity dispersion, larger along the vertical direction than the horizontal ones, which should relate to the assembly history of the Milky Way. Matèria fosca (Astronomia) Cinemàtica galàctica Estructura galàctica Dark matter (Astronomy) Galactic kinematics Galactic structure The oblateness of the Milky Way dark matter halo from the stellar streams of NGC 3201, M68, and Palomar 5