Modelling the Milky Way as a dry Galaxy

Fujii, Michiko S.; Bédorf, Jeroen; Baba, Junichi; Zwart, Simon Portegies

doi:10.1093/mnras/sty2747

Cited by 48 publications

(86 citation statements)

References 68 publications

(133 reference statements)

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“…Interestingly, Asano et al (2020) found higher-order bar resonance features in the self-consistent MW simulation by Fujii et al (2019) that might resemble the velocity structure of the 'Hercules' sub-arches. Their 'Hercules 2', 'Hercules 1', and 'Horn' arches would in this case be associated with 1:5, 1:4, and 1:3 bar resonances.…”

Section: Higher-order Resonances: a Curious Coincidence In Thementioning

confidence: 96%

Identifying resonances of the Galactic bar in Gaia DR2: I. Clues from action space

Trick

Fragkoudi

Hunt

et al. 2020

Monthly Notices of the Royal Astronomical Society

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Action space synthesizes the orbital information of stars and is well-suited to analyse the rich kinematic substructure of the disc in the Gaia DR2 radial velocity sample (RVS). We revisit the strong perturbation induced in the Milky Way (MW) disc by an m = 2 bar, using test particle simulations and the actions (JR, Lz, Jz) estimated in an axisymmetric potential. These make three useful diagnostics cleanly visible. (1.) We use the well-known characteristic flip from outward to inward motion at the Outer Lindblad Resonance (OLR, l = +1, m = 2), which occurs along the axisymmetric resonance line (ARL) in (Lz, JR), to identify in the Gaia action data three candidates for the bar’s OLR and pattern speed Ωbar: 1.85Ω0, 1.20Ω0, and 1.63Ω0 (with ∼0.1Ω0 systematic uncertainty). The Gaia data is therefore consistent with both slow and fast bar models in the literature, but disagrees with recent measurements of ∼1.45Ω0. (2.) For the first time, we demonstrate that bar resonances—especially the OLR—cause a gradient in vertical action 〈Jz〉 with Lz around the ARL via “Jz-sorting” of stars. This could contribute to the observed coupling of 〈vR〉 and 〈|vz|〉 in the Galactic disc. (3.) We confirm prior results that the behaviour of resonant orbits is well approximated by scattering and oscillation in (Lz, JR) along a slope ΔJR/ΔLz = l/m centered on the l:m ARL. Overall, we demonstrate that axisymmetrically estimated actions are a powerful diagnostic tool even in non-axisymmetric systems.

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Section: Higher-order Resonances: a Curious Coincidence In Thementioning

confidence: 96%

Identifying resonances of the Galactic bar in Gaia DR2: I. Clues from action space

Trick

Fragkoudi

Hunt

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…While we still cannot match the resolution of the Gaia data, we can easily pick out several moving groups when selecting regions on the kpc or less scale at the Solar radius. For example, Fujii et al (2019) have previously used Bonsai simulations to examine the vR − v φ plane around the Outer Lindblad Resonance (OLR) of a short fast bar. Similar to previous studies (e.g.…”

Section: Model M1: Planar Dynamics and The Classical Moving Groupsmentioning

confidence: 99%

Resolving local and global kinematic signatures of satellite mergers with billion particle simulations

Hunt

Stelea

Johnston

et al. 2021

Monthly Notices of the Royal Astronomical Society

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In this work we present two new ∼109 particle self-consistent simulations of the merger of a Sagittarius-like dwarf galaxy with a Milky Way-like disc galaxy. One model is a violent merger creating a thick disc, and a Gaia-Enceladus/Sausage like remnant. The other is a highly stable disc which we use to illustrate how the improved phase space resolution allows us to better examine the formation and evolution of structures that have been observed in small, local volumes in the Milky Way, such as the z − vz phase spiral and clustering in the vR − vφ plane when compared to previous works. The local z − vz phase spirals are clearly linked to the global asymmetry across the disc: we find both 2-armed and 1-armed phase spirals, which are related to breathing and bending behaviors respectively. Hercules-like moving groups are common, clustered in vR − vφ in local data samples in the simulation. These groups migrate outwards from the inner galaxy, matching observed metallicity trends even in the absence of a galactic bar. We currently release the best fitting ‘present day’ merger snapshots along with the unperturbed galaxies for comparison.

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“…In order to resolve substructures in the phase-space, we used 120 × 10 6 particles to model the stellar disk component and 61451200 particles to model the dark matter halo, making this model one of the highest resolution N-body simulations of an isolated disk galaxy (see, e.g., Fujii et al 2019;Khoperskov et al 2019;Asano et al 2020). Note however, that the number of particles in a SNd-like region in this high-resolution model is still by a factor of ∼ 5 lower than the number of stars already available in the Gaia RVS sample.…”

Section: Model Descriptionmentioning

confidence: 99%

Chemo-kinematics of the Milky Way spiral arms and bar resonances: connection to ridges and moving groups in the Solar vicinity

Khoperskov,

Gerhard

2021

Preprint

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Making use of a new high-resolution spiral galaxy simulation, as well as Gaia DR2 and EDR3 data complemented by chemical abundances from the Galah DR3, APOGEE DR16, LAMOST DR5 surveys, we explore the possible link between the Milky Way (MW) spiral arms, (R,v φ ) -ridges and moving groups in local v R -v φ space. We show that the tightly wound main spiral arms in the N-body simulation can be successfully identified using overdensities in angular momentum (AM) or guiding space, as well as in the distribution of dynamically cold stars close to their guiding centers. Stars in the AM overdensities that travel over many kpc in radius trace extended density ridges in (R,v φ ) space and overdensities in the v R -v φ plane of a Solar neighbourhood (SNd)-like region, similar to those observed in the Gaia data. Similarly, the AM space of the MW contains several overdensities which correlate with a wave-like radial velocity pattern; this pattern is also reproduced by stars well beyond the SNd. We find that the fraction of Gaia stars located near their guiding centers shows three large-scale structures that approximately coincide with the MW spiral arms traced by distributions of maser sources in the Sagittarius, Local, and Perseus arms. This approach does not work for the Scutum arm near the end of the bar. Similar to the simulation, the stars in the AM overdensities follow the main (R,v φ ) density ridges with nearly constant angular momentum. When these ridges cross the SNd, they can be matched with the main v R -v φ features. Thus we suggest that the Hat is the inner tail of the Perseus arm, one of the Hercules components is the Sagittarius arm and the Arcturus stream is likely to be the outermost tail of the Scutum-Centaurus arm. Based on previous work, the bar corotation is suggested to coincide with the second, v φ ≈ −55 km/s Hercules stream ridge, and the OLR with the Sirius stream. The latter is supported by a sharp decrease of the mean metallicity beyond the Sirius stream, which is an expected behaviour of the OLR, limiting migration of the metal-rich stars from the inner MW. In various phase-space coordinates the AM overdensities stars have systematically higher mean metallicity by about 0.05 dex compared to surrounding stars which is a predicted behaviour of the spiral arms. We show that the wave-like metallicity pattern can be traced at least up to |z| ≈ 1 kpc, linked to radial velocity variations seen even further (|z| ≈ 2 kpc) from the Galactic mid-plane.

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Modelling the Milky Way as a dry Galaxy

Cited by 48 publications

References 68 publications

Identifying resonances of the Galactic bar in Gaia DR2: I. Clues from action space

Identifying resonances of the Galactic bar in Gaia DR2: I. Clues from action space

Resolving local and global kinematic signatures of satellite mergers with billion particle simulations

Chemo-kinematics of the Milky Way spiral arms and bar resonances: connection to ridges and moving groups in the Solar vicinity

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