The GALAH survey: velocity fluctuations in the Milky Way using Red Clump giants

Khanna, Shourya; Sharma, Sanjib; Bland-Hawthorn, Joss; Hayden, Michael R.; Nataf, David M.; Ting, Yuan-Sen; Kos, Janez; Martell, Sarah L.; Zwitter, T.; Silva, Gayandhi De; Asplund, Martin; Buder, Sven; Duong, Ly; Lin, Jane; Simpson, Jeffrey D.; Anguiano, Borja; Horner, Jonathan; Kafle, Prajwal R.; Lewis, Geraint F.; Nordlander, Thomas; Wyse, Rosemary F. Ġ.; Wittenmyer, Robert A.; Zucker, D. B.

doi:10.1093/mnras/sty2924

Cited by 9 publications

(8 citation statements)

References 61 publications

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“…We note that the bimodal kinematic behaviour is also present at smaller R but with smaller amplitude in the vertical velocities. In fact some hints of this bimodality were seen in the maps of, for example, Khanna et al (2019a) and Wang et al (2020b) but those reach only 12 kpc from the Galactic centre and the bimodality appears marginally at the borders of their distributions. Additionally, we note now a clear spatial evolution, with the region at large V * φ and positive V * Z smoothly diminishing its V * φ when R increases.…”

Section: Velocity Correlations and Asymmetriesmentioning

confidence: 89%

“…Widrow et al 2012;Bennett & Bovy 2019), substructure in the in-plane velocities (e.g. Dehnen 1998;Famaey et al 2005;Antoja et al 2008Antoja et al , 2018Kawata et al 2018;Khanna et al 2019a;Fragkoudi et al 2019) large scale velocity patterns in the disc (Siebert et al 2011;Williams et al 2013;Carlin et al 2013;Antoja et al 2017) and other phase space correlations (e.g. Schönrich & Dehnen 2018;Friske & Schönrich 2019;Huang et al 2018;Cheng et al 2020).…”

Section: Introductionmentioning

confidence: 99%

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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: Velocity Correlations and Asymmetriesmentioning

confidence: 89%

Section: Introductionmentioning

confidence: 99%

GaiaEarly Data Release 3

Antoja¹,

McMillan²,

Kordopatis³

et al. 2021

A&A

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“…With SDSS data, Widrow et al (2012) discovered similar wave-like compression or rarefaction features seen in both number density and bulk velocity, as well as towards the Galactic anticentre with LAMOST data (Carlin et al 2013). The large-scale velocity field has also been mapped using highly precise line-of-sight velocities and distance tracers such as red clump giants (Bovy et al 2015;Khanna et al 2019a). (We adopt the term 'line-of-sight velocities' in place of 'radial velocities' for spectroscopically determined heliocentric velocity components in the direction of the source to avoid confusion with galactocentric 'radial velocity'.)…”

Section: Introductionmentioning

confidence: 99%

Gaia Data Release 3

Drimmel¹,

Romero-Gómez²,

Chemin³

et al. 2023

A&A

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Context. With the most recent Gaia data release, the number of sources with complete 6D phase space information (position and velocity) has increased to well over 33 million stars, while stellar astrophysical parameters are provided for more than 470 million sources, and more than 11 million variable stars are identified. Aims. Using the astrophysical parameters and variability classifications provided in Gaia DR3 , we selected various stellar populations to explore and identify non-axisymmetric features in the disc of the Milky Way in configuration and velocity space. Methods. Using more about 580 000 sources identified as hot OB stars, together with 988 known open clusters younger than 100 million years, we mapped the spiral structure associated with star formation 4-5 kpc from the Sun. We selected over 2800 Classical Cepheids younger than 200 million years that show spiral features extending as far as 10 kpc from the Sun in the outer disc. We also identified more than 8.7 million sources on the red giant branch (RGB), of which 5.7 million have line-of-sight velocities. This later sample allows the velocity field of the Milky Way to be mapped as far as 8 kpc from the Sun, including the inner disc. Results. The spiral structure revealed by the young populations is consistent with recent results using Gaia EDR3 astrometry and source lists based on near-infrared photometry, showing the Local (Orion) Arm to be at least 8 kpc long, and an Outer Arm consistent with what is seen in HI surveys, which seems to be a continuation of the Perseus arm into the third quadrant. The subset of RGB stars with velocities clearly reveals the large-scale kinematic signature of the bar in the inner disc, as well as evidence of streaming motions in the outer disc that might be associated with spiral arms or bar resonances. A local comparison of the velocity field of the OB stars reveals similarities and differences with the RGB sample. Conclusions. This cursory study of Gaia DR3 data shows there is a rich bounty of kinematic information to be explored more deeply, which will undoubtedly lead us to an understanding of the dynamical nature of the non-axisymmetric structures of the Milky Way.

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“…The co-moving pairs identified in K19b along with wide binaries from other work (e.g., Andrews et al 2017;El-Badry & Rix 2018a;Hawkins et al 2020) probe (by design) fairly small spatial scales (1−20 pc). Other work studying resonances (e.g., Bovy et al 2015;Khanna et al 2019) probe structure at kiloparsec scales. Here we expand upon previous work by measuring the twopoint correlation function for the solar neighborhood on physical scales from parsecs to kiloparsecs in order to study the clustered nature of the Galaxy.…”

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confidence: 99%

“…There has been some previous work characterizing the clustering in the Galactic halo (Cooper et al 2011;Lancaster et al 2019) to study kinematic substrutures and infer the Galactic accretion history. Bovy et al (2015) and Khanna et al (2019) calculated the power spectrum (the fourier tranform of the TPCF) of velocity fluctuations in the disk to study the dynamical influence of the bar in the disk. Mao et al (2015) used the TPCF to probe Galactic disk structure in SEGUE G-Dwarf stars.…”

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confidence: 99%

Spatial and Kinematic Clustering of Stars in the Galactic Disk

Kamdar,

Conroy,

Ting

et al. 2020

Preprint

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The Galactic disk is expected to be spatially, kinematically, and chemically clustered on many scales due to both star formation and non-axisymmetries in the Galactic potential. In this work we calculate the spatial and kinematic two-point correlation functions using a sample of 1.7 × 10 6 stars within 1 kpc of the Sun with 6D phase space information available from Gaia DR2. Clustering is detected on spatial scales of 1 − 300 pc and velocity scales of at least 15 km s −1 . With bound structures included, the data have a power-law index (ξ(∆r) ∝ ∆r γ ) of γ ≈ −2 at most spatial scales, which is in line with theoretical predictions. After removing bound structures, the data have a power-law index of γ ≈ −1 for 1 < ∆r < 100 pc and γ −1.5 for > 100 pc. We interpret these results with the aid of a novel star-by-star simulation of the Galaxy in which stars are born in clusters orbiting in a realistic potential that includes spiral arms, a bar, and giant molecular clouds (GMCs). We find that the simulation largely agrees with the observations (within a factor of 2 − 3) at all spatial and kinematic scales. In detail, the correlation function in the simulation is shallower than the data at 20 pc scales, and steeper than the data at 30 pc scales. We also find a persistent clustering signal in the kinematic correlation function for the data at large ∆v (> 5 km s −1 ) that is not present in the simulations. We speculate that this mismatch between observations and simulations may be due to two processes not included in the present simulation: hierarchical star formation and transient spiral arms. We also use these simulations to predict the clustering signal as a function of pair-wise metallicity and age separations. Ages and metallicities measured with a precision of 50% and 0.05 dex, respectively, are required in order to enhance the clustering signal beyond the current measurements.

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The GALAH survey: velocity fluctuations in the Milky Way using Red Clump giants

Cited by 9 publications

References 61 publications

GaiaEarly Data Release 3

GaiaEarly Data Release 3

Gaia Data Release 3

Spatial and Kinematic Clustering of Stars in the Galactic Disk

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