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Stellar halo substructure generated by bar resonances

Accepted version
Peer-reviewed

Type

Article

Change log

Authors

Evans, NW 
Davies, EY 

Abstract

jats:titleABSTRACT</jats:title> jats:pUsing data from the Gaia satellite’s Radial Velocity Spectrometer Data Release 3 (RVS, DR3), we find a new and robust feature in the phase-space distribution of halo stars. It is a prominent ridge at constant energy and with angular momentum Lz &gt; 0. We run test particle simulations of a stellar halo-like distribution of particles in a realistic Milky Way potential with a rotating bar. We observe similar structures generated in the simulations from the trapping of particles in resonances with the bar, particularly at the corotation resonance. Many of the orbits trapped at the resonances are halo like, with large vertical excursions from the disc. The location of the observed structure in energy space is consistent with a bar pattern speed in the range Ωb ≈ 35−40 km s−1 kpc−1. Overall, the effect of the resonances is to give the inner stellar halo a mild, net spin in the direction of the bar’s rotation. As the distribution of the angular momentum becomes asymmetric, a population of stars with positive mean Lz and low vertical action is created. The variation of the average rotational velocity of the simulated stellar halo with radius is similar to the behaviour of metal-poor stars in data from the APOGEE survey. Though the effects of bar resonances have long been known in the Galactic disc, this is strong evidence that the bar can drive changes even in the diffuse and extended stellar halo through its resonances.</jats:p>

Description

Keywords

Galaxy: halo, Galaxy: kinematics and dynamics, Galaxy: structure

Journal Title

Monthly Notices of the Royal Astronomical Society

Conference Name

Journal ISSN

0035-8711
1365-2966

Volume Title

Publisher

Oxford University Press (OUP)