Spatial and Kinematic Clustering of Stars in the Galactic Disk

Kamdar, Harshil; Conroy, Charlie; Ting, Yuan-Sen; El-Badry, Kareem

doi:10.48550/arxiv.2007.10990

Cited by 4 publications

(4 citation statements)

References 68 publications

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“…In this transient scenario, R c is not an important parameter since the spiral arms would co-rotate with stars at their galactocentric radii, causing short-lived arms. A number of authors looking at the field population, some using simulation-based approaches, tend to favour a transient nature for the spirals (Quillen et al 2018;Hunt et al 2020;Kamdar et al 2020).…”

Section: Introductionmentioning

confidence: 99%

Milky Way spiral arms from open clusters in Gaia EDR3

Castro-Ginard

McMillan

Luri

et al. 2021

A&A

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Context. The physical processes driving the formation of Galactic spiral arms are still under debate. Studies using open clusters favour the description of the Milky Way spiral arms as long-lived structures following the classical density wave theory. Current studies comparing the Gaia DR2 field stars kinematic information of the solar neighbourhood to simulations, find a better agreement with short-lived arms with a transient behaviour. Aims. Our aim is to provide an observational, data-driven view of the Milky Way spiral structure and its dynamics using open clusters as the main tracers, and to contrast it with simulation-based approaches. We used the most complete catalogue of Milky Way open clusters, with astrometric Gaia EDR3 updated parameters, estimated astrophysical information, and radial velocities, to revisit the nature of the spiral pattern of the Galaxy. Methods. We used a Gaussian mixture model to detect overdensities of open clusters younger than 30 Myr that correspond to the Perseus, Local, Sagittarius, and Scutum spiral Arms, respectively. We used the birthplaces of the open cluster population younger than 80 Myr to trace the evolution of the different spiral arms and compute their pattern speed. We analysed the age-distribution of the open clusters across the spiral arms to explore the differences in the rotational velocity of stars and spiral arms. Results. We are able to increase the range in Galactic azimuth where present-day spiral arms are described, better estimating its parameters by adding 264 young open clusters to the 84 high-mass star-forming regions used so far, thus increasing the number of tracers by 314%. We used the evolution of the open clusters from their birth positions to find that spiral arms nearly co-rotate with field stars at any given radius, discarding a common spiral pattern speed for the spiral arms explored. Conclusions. The derivation of different spiral pattern speeds for the different spiral arms disfavours classical density waves as the main drivers for the formation of the Milky Way spiral structure, and it is in better agreement with simulation-based approaches that tend to favour transient spirals. The increase in the number of known open clusters, as well as in their derived properties, allows us to use them as effective spiral structure tracers and homogenise the view from open clusters and field stars on the nature of the Galactic spiral arms.

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Section: Introductionmentioning

confidence: 99%

Milky Way spiral arms from open clusters in Gaia EDR3

Castro-Ginard

McMillan

Luri

et al. 2021

A&A

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“…The dependence of parallax, proper motion and radial velocity errors is a complex function of several parameters. We follow the procedure set out in Kamdar et al (2019bKamdar et al ( , 2020 to build the error model for the simulations. Briefly, we fit a Gaussian mixture model (GMM) with 20 components to the combined (G, G BP − G RP , σ , σ µ α * , σ µ δ ) and (G, G BP − G RP , σ RV ) spaces respectively for both DR2 and EOM errors, where σ , σ µ α * , σ µ δ , σ RV are the uncertainties in the parallax, proper motions and the radial velocities.…”

Section: Simulations 21 Simulationsmentioning

confidence: 99%

Stellar Streams in the Galactic Disk: Predicted Lifetimes and Their Utility in Measuring the Galactic Potential

Kamdar,

Conroy,

Ting

2021

Preprint

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In this paper we present a holistic view of the detection, characterization, and origin of stellar streams in the disk of a simulated Milky Way-like galaxy. The star-by-star simulation of the Galaxy evolves stars born in clusters in a realistic galactic potential that includes spiral arms, a bar, and giant molecular clouds over 5 Gyr. We first devise a new hybrid method to detect stellar streams that combines phase space density information along with the action-angle space spanned by stars in our simulation. We find that streams' progenitor star clusters and associations are all preferentially higher-mass (> 1000 M ) and young (< 1 Gyr). Our stream-finding method predicts that we might be able to find anywhere from 1 to 10 streams with 6D Gaia DR2 data in the solar neighborhood alone. The simulation suggests that streams are sensitive to the initial dynamical state of clusters, accumulated energy gain from encounters with giant molecular clouds (GMCs), and present-day actions. We investigate what we can learn about the Galactic potential by studying the feasiblity of rewinding stellar streams back to their origin. Even with perfect information about the non-axisymmetric components (spiral arms, bar) of the galactic potential, the stochastic GMC population makes backwards integration impossible beyond one or two disk orbital times. Streams are also sensitive to the properties of the bar, but fairly insensitive to the properties of the non-transient two-armed spiral in our simulation. Finally we predict that around 10 to 30 stellar streams should be detectable with Gaia's 10-year end-of-mission data. There are many more stellar streams waiting to be discovered in the Galactic disk, and they could hold clues about the history of the Galaxy for the past Gyr.

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“…In this transient scenario R c is not an important parameter since the spiral arms would co-rotate with stars at their Galactocentric radius, causing short-lived arms. A number of authors looking at the field population, some using simulation-based approaches, tended to favour a transient nature for the spirals (Quillen et al 2018;Hunt et al 2020;Kamdar et al 2020).…”

Section: Introductionmentioning

confidence: 99%

On the Milky Way spiral arms from open clusters in Gaia EDR3

Castro-Ginard,

McMillan,

Luri

et al. 2021

Preprint

View full text Add to dashboard Cite

Context. The physical processes driving the formation of Galactic spiral arms are still under debate. Studies using open clusters favour the description of the Milky Way spiral arms as long-lived structures following the classical density wave theory. Current studies comparing the Gaia DR2 field stars kinematic information of the Solar neighbourhood to simulations, find a better agreement with short-lived arms with a transient behaviour. Aims. Our aim is to provide an observational, data-driven view of the Milky Way spiral structure and its dynamics using open clusters as the main tracers, and to contrast it with simulation-based approaches. We use the most complete catalogue of Milky Way open clusters, with astrometric Gaia EDR3 updated parameters, estimated astrophysical information and radial velocities, to re-visit the nature of the spiral pattern of the Galaxy. Methods. We use a Gaussian mixture model to detect overdensities of open clusters younger than 30 Myr that correspond to the Perseus, Local, Sagittarius and Scutum spiral arms, respectively. We use the birthplaces of the open cluster population younger than 80 Myr to trace the evolution of the different spiral arms and compute their pattern speed. We analyse the age-distribution of the open clusters across the spiral arms to explore the differences in the rotational velocity of stars and spiral arms. Results. We are able to increase the range in Galactic azimuth where present-day spiral arms are described, better estimating its parameters by adding 264 young open clusters to the 84 high-mass star forming regions used so far, thus increasing by a 314% the number of tracers. We use the evolution of the open clusters from their birth positions to find that spiral arms nearly co-rotate with field stars at any given radius, discarding a common spiral pattern speed for the spiral arms explored. Conclusions. The derivation of different spiral pattern speeds for the different spiral arms disfavours classical density waves as the main drivers for the formation of the Milky Way spiral structure, and is in better agreement with simulation-based approaches that tend to favour transient spirals. The increase in the number of known open clusters, as well as in their derived properties allows us to use them as effective spiral structure tracers, and homogenise the view from open clusters and field stars on the nature of the Galactic spiral arms.

show abstract

Spatial and Kinematic Clustering of Stars in the Galactic Disk

Cited by 4 publications

References 68 publications

Milky Way spiral arms from open clusters in Gaia EDR3

Milky Way spiral arms from open clusters in Gaia EDR3

Stellar Streams in the Galactic Disk: Predicted Lifetimes and Their Utility in Measuring the Galactic Potential

On the Milky Way spiral arms from open clusters in Gaia EDR3

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