Footprints of the Sagittarius dwarf galaxy in the Gaia data set

Laporte, Chervin F. P.; Minchev, Ivan; Johnston, Kathryn V.; Gómez, Facundo A.

doi:10.1093/mnras/stz583

Cited by 288 publications

(350 citation statements)

References 112 publications

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“…They find that velocity fields can be highly sensitive to the nature of spiral arms, be they bar driven, density wave-like, or seeded by disc instabilities. In Laporte et al (2019) the authors use N -body simulations of a Milky Way type disc and the interaction with the infalling Sagittarius-like dwarf galaxy, producing a remarkable correspondence to the Gaia DR2 velocity maps (see also Bland-Hawthorn et al 2019). Though the maximum velocity variations are nearly double what is seen in the DR2 data, similar to our maps.…”

Section: Gaia Dr2 Comparisonsupporting

confidence: 77%

Young stars as tracers of a barred-spiral Milky Way

Pettitt

Ragan

Smith

2019

Monthly Notices of the Royal Astronomical Society

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Identifying the structure of our Galaxy has always been fraught with difficulties, and while modern surveys continue to make progress building a map of the Milky Way, there is still much to understand. The arm and bar features are important drivers in shaping the interstellar medium, but their exact nature and influence still require attention. We present results of smoothed particle hydrodynamic simulations of gas in the Milky Way including star formation, stellar feedback, and ISM cooling, when exposed to different arm and bar features, with the aim of better understanding how well newly formed stars trace out the underlying structure of the Galaxy. The bar is given a faster pattern speed than the arms, resulting in a complex, time-dependent morphology and star formation. Inter-arm branches and spurs are easily influenced by the bar, especially in the two-armed spiral models where there is a wide region of resonance overlap in the disc. As the bar over-takes the spiral arms it induces small boosts in star formation and enhances spiral features, which occur at regularly spaced beat-like intervals. The locations of star formation events are similar to those seen in observational data, and do not show a perfect 1:1 correspondence with the underlying spiral potential, though arm tangencies are generally well traced by young stars. Stellar velocity fields from the newly formed stars are compared to data from Gaia DR2, showing that the spiral and bar features can reproduce many of the nonaxisymmetric features seen in the data. A simple analytical model is used to show many of these feature are a natural response of gas to rigidly rotating spiral and bar potentials.

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Section: Gaia Dr2 Comparisonsupporting

confidence: 77%

Young stars as tracers of a barred-spiral Milky Way

Pettitt

Ragan

Smith

2019

Monthly Notices of the Royal Astronomical Society

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“…The phase overlap between the observed density and metallicity asymmetries can satisfactorily be explained by the phase-space wrapping of stars in the Z-V Z plane, which has recently been discovered by Gaia (Antoja et al 2018;Binney & Schönrich 2018;Bland-Hawthorn et al 2019;Darling & Widrow 2019;Laporte et al 2019).…”

Section: Summary and Discussionmentioning

confidence: 65%

Asymmetric Mean Metallicity Distribution of the Milky Way’s Disk

2019

ApJL

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I present the mean metallicity distribution of stars in the Milky Way Galaxy based on photometry from the Sloan Digital Sky Survey. I utilize an empirically calibrated set of stellar isochrones developed in previous work to estimate the metallicities of individual stars to a precision of 0.2 dex for reasonably bright stars across the survey area. I also obtain more precise metallicity estimates using priors from the Gaia parallaxes for relatively nearby stars. Close to the Galactic mid-plane (|Z| < 2 kpc), a mean metallicity map reveals deviations from the mirror symmetry between the northern and southern hemispheres, displaying wave-like oscillations. The observed metallicity asymmetry structure is almost parallel to the Galactic mid-plane, and coincides with the previously known asymmetry in the stellar number density distribution. This result reinforces the previous notion of the plane-parallel vertical waves propagating through the disk, in which a local metallicity perturbation from the mean vertical metallicity gradient is induced by the phase-space wrapping of stars in the Z-V Z plane. The maximum amplitude of the metallicity asymmetry (∆[Fe/H]∼ 0.05) implies that these stars have been pulled away from the Galactic mid-plane by an order of ∆|Z| ∼ 80 pc as a massive halo substructure such as the Sagittarius dwarf galaxy plunged through the Milky Way. This work provides evidence that the Gaia phase-space spiral may continue out to |Z| ∼ 1.5 kpc.

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“…The Galactic warp is a large-scale distortion of the outer disc with respect to the inner disc, bearing witness that the disc of our Galaxy may be subject to external torques. Proposed mechanisms include torques from a misalignment of the disc's rotation axis with respect to the principle axis of a non-spherical halo 4,5 , or from accreted matter in the halo acquired during late infall 6,7 , or from nearby, interacting satellite galaxies and their consequent tides 8,9 . However, the cause and dynamical nature of the warp of our Galaxy has remained unclear due to a lack of kinematic constraints.…”

Section: Mainmentioning

confidence: 99%

Evidence of a dynamically evolving Galactic warp

et al. 2020

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In a cosmological setting the disc of a galaxy is expected to continuously experience gravitational torques and perturbations from a variety of sources, which can cause the disc to wobble, flare and warp 1, 2 . Specifically, the study of galactic warps and their dynamical nature can potentially reveal key information on the formation history of galaxies and the mass distribution of their halos. Our Milky Way presents a unique case study for galactic warps, thanks to detailed knowledge of its stellar distribution and kinematics. Using a simple model of how the warp's orientation is changing with time, we here measure for the first time the precession rate of the Milky Way's warp using 12 million giant stars from Gaia Data Release 2 3 , finding that it is precessing at 10.46 ± 0.03 stat ± 2.72 syst km s −1 kpc −1 in the direction of Galactic rotation, about one third the angular rotation velocity at the Sun's position in the Galaxy. The direction and magnitude of the warps precession rate favour the scenario that the warp is the result of a recent or ongoing encounter with a satellite galaxy, rather than the relic of the ancient assembly history of the Galaxy. 1

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Footprints of the Sagittarius dwarf galaxy in the Gaia data set

Cited by 288 publications

References 112 publications

Young stars as tracers of a barred-spiral Milky Way

Young stars as tracers of a barred-spiral Milky Way

Asymmetric Mean Metallicity Distribution of the Milky Way’s Disk

Evidence of a dynamically evolving Galactic warp

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