Chemodynamical Signatures of Bar Resonances in the Galactic Disk: Current Data and Future Prospects

Wheeler, Adam; Abril-Cabezas, Irene; Trick, Wilma H.; Fragkoudi, Francesca; Ness, Melissa

doi:10.3847/1538-4357/ac7da0

Cited by 8 publications

(2 citation statements)

References 99 publications

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“…Subsequently, Dehnen (1998) used HIPPARCOS data to demonstrate the existence of abundant substructure or moving groups in the disc, which he ascribed partly to resonance effects. The Gaia data releases have revealed abundant ridges, undulations and streams in velocity or action space, sculpted by the Galactic bar (e.g., Fragkoudi et al 2019;Khoperskov et al 2020;Trick et al 2021;Trick 2022;Wheeler et al 2022).…”

Section: Introductionmentioning

confidence: 99%

Stellar halo substructure generated by bar resonances

Belokurov

Evans

et al. 2023

Monthly Notices of the Royal Astronomical Society

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Using 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 > 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.

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Section: Introductionmentioning

confidence: 99%

Stellar halo substructure generated by bar resonances

Belokurov

Evans

et al. 2023

Monthly Notices of the Royal Astronomical Society

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“…Particles can become trapped by these resonances, creating overdense structures in the phase space (Debattista & Sellwood 2000;Sellwood 2010;Gerhard 2011;McMillan 2013;Binney 2020;. Much attention has been given to such structures in the stellar disk, particularly since data from the Gaia observatory (Gaia Collaboration et al 2016) became available (Fragkoudi et al 2019;Khoperskov et al 2020;Trick et al 2021;Khoperskov & Gerhard 2022;Trick 2022;Wheeler et al 2022). However, stars orbiting in the halo can also become trapped, creating moving groups and substructure on more eccentric and inclined orbits (Moreno et al 2015(Moreno et al , 2021Dillamore et al 2023Dillamore et al , 2024.…”

Section: Introductionmentioning

confidence: 99%

Trojan Globular Clusters: Radial Migration via Trapping in Bar Resonances

Dillamore,

Monty,

Belokurov

et al. 2024

ApJL

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We search for globular clusters (GCs) trapped in resonances with the bar of the Milky Way (MW). By integrating their orbits in a potential with a decelerating bar, we select 10 whose orbits are significantly changed by its presence. Most of these are trapped in the corotation resonance, including M22 and 47 Tuc. The decelerating bar is capable of transporting these GCs to their current positions from much lower energies, angular momenta, and radii. Our results indicate that the bar is likely to have reshaped the MW’s GC system via its resonances. We also discuss implications for the origins of specific GCs, including the possible nuclear star cluster M22. Finally, we consider the effects of the bar on the tidal tails of a trapped GC by running simulations of stars stripped from 47 Tuc. Instead of forming narrow tails, the stripped stars make up a diffuse extended halo around the cluster, consistent with observations of 47 Tuc.

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Timing the Milky Way bar formation and the accompanying radial migration episode

Haywood,

Khoperskov,

Cerqui

et al. 2024

A&A

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We derived the metallicity profile of the Milky Way low-alpha disc population from 2 to 20 kpc from the Galactic centre in 1 Gyr age bins using the astroNN catalogue, and we show that it is highly structured, with a plateau between 4 and 7 kpc and a break at 10-12 kpc. We argue that these features result from the two main bar resonances, the corotation and the outer Lindblad resonance (OLR), respectively. We show that the break in the metallicity profile is most visible in stars having 7-8 Gyr, reaching an amplitude of about 0.4 dex, and it is the signpost of the position of the bar OLR. The bar formation was accompanied by an episode of radial migration triggered by it slowing down and it is responsible for spreading old metal-rich stars up to the OLR. The data show that the slowdown of the bar ended 6-7 Gyr ago. Based on numerical simulations that reproduce well the characteristic break observed in the metallicity profile, we argue that this implies that the bar formed in our Galaxy 8-10 Gyr ago. Analysis of the metallicity distribution as a function of radius shows no evidence of significant systematic outward radial migration after this first episode. We argue that the variation of the metallicity dispersion as a function of the guiding radius is dominated by the migration triggered by the bar, but also that the libration of orbits around the bar resonances induces a mixing that may have a significant impact on the observed metallicity dispersion. In contrast, the absence of a break in the metallicity profile of populations younger than sim 6 Gyr and the flattening of the gradient at younger ages is interpreted as evidence that the strength of the bar has decreased, loosening its barrier effect and allowing the gas and metals on both sides of the OLR to mix, erasing the break. Beyond the OLR, stars younger than 7 Gyr show very small metallicity dispersion, suggesting that no or limited mixing induced by the spiral arms has occurred in the outer disc.

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Chemodynamical Signatures of Bar Resonances in the Galactic Disk: Current Data and Future Prospects

Cited by 8 publications

References 99 publications

Stellar halo substructure generated by bar resonances

Stellar halo substructure generated by bar resonances

Trojan Globular Clusters: Radial Migration via Trapping in Bar Resonances

Timing the Milky Way bar formation and the accompanying radial migration episode

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