The GALAH survey and Gaia DR2: Linking ridges, arches, and vertical waves in the kinematics of the Milky Way

Khanna, Shourya; Sharma, Sanjib; Tepper-García, Thor; Bland-Hawthorn, Joss; Hayden, Michael R.; Asplund, Martin; Buder, Sven; Chen, Boquan; Silva, Gayandhi M. De; Freeman, K. C.; Kos, Janez; Lewis, Geraint F.; Lin, Jane; Martell, Sarah L.; Simpson, Jeffrey D.; Nordlander, Thomas; Stello, Dennis; Ting, Yuan-Sen; Zucker, D. B.; Zwitter, T.

doi:10.1093/mnras/stz2462

Cited by 88 publications

(95 citation statements)

References 68 publications

(92 reference statements)

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“…14b the ridges exhibit a complex pattern of positive and negative vertical velocities, thus indicating coupling between in-plane and off-plane kinematics. These effects were also noticed in Gaia DR2 with the RVS sample (Khanna et al 2019b;Laporte et al 2019a), where the ridges were stronger at lower Z and had some amplitude in V * Z though typically lower than 5 km s −1 .…”

Section: Small Scale Velocity Structuresmentioning

confidence: 58%

GaiaEarly Data Release 3

Antoja¹,

McMillan²,

Kordopatis³

et al. 2021

A&A

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Aims. We aim to demonstrate the scientific potential of the Gaia Early Data Release 3 (EDR3) for the study of different aspects of the Milky Way structure and evolution and we provide, at the same time, a description of several practical aspects of the data and examples of their usage. Methods. We used astrometric positions, proper motions, parallaxes, and photometry from EDR3 to select different populations and components and to calculate the distances and velocities in the direction of the anticentre. In this direction, the Gaia astrometric data alone enable the calculation of the vertical and azimuthal velocities; also, the extinction is relatively low compared to other directions in the Galactic plane. We then explore the disturbances of the current disc, the spatial and kinematical distributions of early accreted versus in situ stars, the structures in the outer parts of the disc, and the orbits of open clusters Berkeley 29 and Saurer 1. Results. With the improved astrometry and photometry of EDR3, we find that: (i) the dynamics of the Galactic disc are very complex with oscillations in the median rotation and vertical velocities as a function of radius, vertical asymmetries, and new correlations, including a bimodality with disc stars with large angular momentum moving vertically upwards from below the plane, and disc stars with slightly lower angular momentum moving preferentially downwards; (ii) we resolve the kinematic substructure (diagonal ridges) in the outer parts of the disc for the first time; (iii) the red sequence that has been associated with the proto-Galactic disc that was present at the time of the merger with Gaia-Enceladus-Sausage is currently radially concentrated up to around 14 kpc, while the blue sequence that has been associated with debris of the satellite extends beyond that; (iv) there are density structures in the outer disc, both above and below the plane, most probably related to Monoceros, the Anticentre Stream, and TriAnd, for which the Gaia data allow an exhaustive selection of candidate member stars and dynamical study; and (v) the open clusters Berkeley 29 and Saurer 1, despite being located at large distances from the Galactic centre, are on nearly circular disc-like orbits. Conclusions. Even with our simple preliminary exploration of the Gaia EDR3, we demonstrate how, once again, these data from the European Space Agency are crucial for our understanding of the different pieces of our Galaxy and their connection to its global structure and history.

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Section: Small Scale Velocity Structuresmentioning

confidence: 58%

GaiaEarly Data Release 3

Antoja¹,

McMillan²,

Kordopatis³

et al. 2021

A&A

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“…In our plot, the clusters seem to qualitatively follow the distribution of diagonal overdensities described by the ridges, at least the most prominent ones. The recent N-body simulations by Khanna et al (2019) suggest that the ridges are more prominent for stars close to the plane with solar metallicity; these conditions are generally met by a sample of OCs. Probably because of the shape of these ridges, the velocity gradient of V φ decreases towards large radii, which is more clearly visible in the plot that shows the entire cluster sample.…”

Section: Kinematics Of Ocs Compared With Field Starsmentioning

confidence: 96%

“…The solar neighbourhood is known to be clumpy (e.g., Eggen 1996;Dehnen & Binney 1998;Antoja et al 2012), and the relation of observed substructures to some OCs, in particular the Hyades, is established (Eggen 1958;Chereul et al 1999). While stellar streams were initially thought to be remnants of star clusters, their origin is now thought to be the result of the disruption of star clusters or of dynamical origin, such as the resonant trapping by the bar and spiral arms (Famaey et al 2008) or the passage of the Sagittarius dwarf galaxy within the The tables with star and cluster velocities are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/647/ A19 Galactic plane (Monari et al 2018;Khanna et al 2019). Stellar streams could also originate from a combination of these processes.…”

Section: Introductionmentioning

confidence: 99%

3D kinematics and age distribution of the open cluster population

Tarricq

Soubiran

Casamiquela

et al. 2021

A&A

135

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Context. Open clusters (OCs) trace the evolution of the Galactic disc with great accuracy. Gaia and large ground-based spectroscopic surveys make it possible to determine their properties and study their kinematics with unprecedented precision. Aims. We study the kinematical behaviour of the OC population over time. We take advantage of the latest age determinations of OCs to investigate the correlations of the 6D phase-space coordinates and orbital properties with age. The phase-space distribution, age-velocity relation, and action distribution are compared to those of field stars. We also investigate the rotation curve of the Milky Way traced by OCs, and we compare it to that of other observational or theoretical studies. Methods. We gathered nearly 30 000 radial velocity (RV) measurements of OC members from both Gaia-RVS data and ground-based surveys and catalogues. We computed the weighted mean RV, Galactic velocities, and orbital parameters of 1382 OCs. We investigated their distributions as a function of age and by comparison to field stars. Results. We provide the largest RV catalogue available for OCs, half of it based on at least three members. Compared to field stars, we note that OCs are not on exactly the same arches in the radial-azimuthal velocity plane, while they seem to follow the same diagonal ridges in the Galactic radial distribution of azimuthal velocities. Velocity ellipsoids in different age bins all show a clear anisotropy. The heating rate of the OC population is similar to that of field stars for the radial and azimuthal components, but it is significantly lower for the vertical component. The rotation curve drawn by our sample of clusters shows several dips that match the wiggles derived from nonaxisymmetric models of the Galaxy. From the computation of orbits, we obtain a clear dependence of the maximum height and eccentricity on age. Finally, the orbital characteristics of the sample of clusters as shown by the action variables follow the distribution of field stars. The additional age information of the clusters indicates some (weak) age dependence of the known moving groups.

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“…Many scenarios have been proposed to explain the dynamical mechanism responsible for the formation of the diagonal ridges, which Wang et al (2020) classify in two types: external perturbations, like the Sagittarius dwarf galaxy perturbation (e.g., Antoja et al, 2018;Bland-Hawthorn et al, 2019;Khanna et al, 2019;Laporte et al, 2019); and internal dynamics, like spiral-arm resonances, buckling of the central bar, etc. (e.g., Quillen et al, 2018;Fragkoudi et al, 2019;Khoperskov et al, 2019;Barros et al, 2020).…”

Section: Diagonal Ridges On the R-v θ Planementioning

confidence: 99%

Dynamics of the Spiral-Arm Corotation and Its Observable Footprints in the Solar Neighborhood

Barros¹,

Pérez-Villegas

Michtchenko

et al. 2021

Front. Astron. Space Sci.

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This article discusses the effects of the spiral-arm corotation on the stellar dynamics in the Solar Neighborhood (SN). All our results presented here rely on: (1) observational evidence that the Sun lies near the corotation circle, where stars rotate with the same angular velocity as the spiral-arm pattern; the corotation circle establishes domains of the corotation resonance (CR) in the Galactic disk; (2) dynamical constraints that put the spiral-arm potential as the dominant perturbation in the SN, comparing with the effects of the central bar in the SN; (3) a long-lived nature of the spiral structure, promoting a state of dynamical relaxing and phase-mixing of the stellar orbits in response to the spiral perturbation. With an analytical model for the Galactic potential, composed of an axisymmetric background deduced from the observed rotation curve, and perturbed by a four-armed spiral pattern, numerical simulations of stellar orbits are performed to delineate the domains of regular and chaotic motions shaped by the resonances. Such studies show that stars can be trapped inside the stable zones of the spiral CR, and this orbital trapping mechanism could explain the dynamical origin of the Local arm of the Milky Way (MW). The spiral CR and the near high-order epicyclic resonances influence the velocity distribution in the SN, creating the observable structures such as moving groups and their radially extended counterpart known as diagonal ridges. The Sun and most of the SN stars evolve inside a stable zone of the spiral CR, never crossing the main spiral-arm structure, but oscillating in the region between the Sagittarius-Carina and Perseus arms. This orbital behavior of the Sun brings insights to our understanding of questions concerning the solar system evolution, the Earth environment changes, and the preservation of life on Earth.

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The GALAH survey and Gaia DR2: Linking ridges, arches, and vertical waves in the kinematics of the Milky Way

Cited by 88 publications

References 68 publications

GaiaEarly Data Release 3

GaiaEarly Data Release 3

3D kinematics and age distribution of the open cluster population

Dynamics of the Spiral-Arm Corotation and Its Observable Footprints in the Solar Neighborhood

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