Origin and structure of the Galactic disc(s)

Schönrich, Ralph; Binney, James

doi:10.1111/j.1365-2966.2009.15365.x

Cited by 316 publications

(317 citation statements)

References 28 publications

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“…Therefore, we argue that a pre-existing thick disc at the time of bar formation, whether as part of a continuum with the thin disc (Brook et al 2004;Schönrich & Binney 2009;Loebman et al 2011;Bird et al 2013;Bovy et al 2012), or as the separate distinct structure envisaged by Bekki & Tsujimoto (2011), is not necessary to produce the chemical trends observed in the Milky Way bulge. However, it is not inconceivable that the oldest population evolves into what, structurally, is consistent with the present-day thick disc.…”

Section: Is a Thick Disc Necessary?mentioning

confidence: 99%

Separation of stellar populations by an evolving bar: implications for the bulge of the Milky Way

Debattista

Ness

Gonzalez

et al. 2017

Monthly Notices of the Royal Astronomical Society

148

255

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We present a novel interpretation of the previously puzzling different behaviours of stellar populations of the Milky Way's bulge. We first show, by means of pure N -body simulations, that initially co-spatial stellar populations with different in-plane random motions separate when a bar forms. The radially cooler populations form a strong bar, and are vertically thin and peanut-shaped, while the hotter populations form a weaker bar and become a vertically thicker box. We demonstrate that it is the radial, not the vertical, velocity dispersion that dominates this evolution. Assuming that early stellar discs heat rapidly as they form, then both the in-plane and vertical random motions correlate with stellar age and chemistry, leading to different density distributions for metal-rich and metal-poor stars. We then use a high-resolution simulation, in which all stars form out of gas, to demonstrate that this is what happens. When we apply these results to the Milky Way we show that a very broad range of observed trends for ages, densities, kinematics and chemistries, that have been presented as evidence for contradictory paths to the formation of the bulge, are in fact consistent with a bulge which formed from a continuum of disc stellar populations which were kinematically separated by the bar. For the first time we are able to account for the bulge's main trends via a model in which the bulge formed largely in situ. Since the model is generic, we also predict the general appearance of stellar population maps of external edge-on galaxies.

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Section: Is a Thick Disc Necessary?mentioning

confidence: 99%

Separation of stellar populations by an evolving bar: implications for the bulge of the Milky Way

Debattista

Ness

Gonzalez

et al. 2017

Monthly Notices of the Royal Astronomical Society

148

255

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“…Several works (e.g., Loebman et al 2011;Schönrich & Binney 2009b) have also proposed that radial migration can give rise to thick disc formation by bringing out high-velocity-dispersion stellar populations from the inner disc and the bulge. More detailed dynamical studies Minchev et al 2012a;Vera-Ciro et al 2014) have more recently shown that migration does not contribute to any significant level to disc thickening, but on the opposite, it suppresses flaring when external perturbations are included (Grand et al 2016;Minchev et al 2014a).…”

Section: The Galactic Thick Discmentioning

confidence: 99%

“…Such a scenario was used, for example, in the analytical model of Schönrich & Binney (2009b), where the authors claimed to explain the Milky Way thickand thin-disc characteristics (both chemical and kinematical) without the need of mergers or any discrete heating processes. Similarly, the increase of disc thickness with time found in the simulation by Roškar et al (2008) has been attributed to migration in the work by Loebman et al (2011).…”

Section: Migration and Disc Thickeningmentioning

confidence: 99%

Constraining the Milky Way assembly history with Galactic Archaeology

Minchev

2016

Astron Nachr

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The aim of Galactic Archaeology is to recover the evolutionary history of the Milky Way from its present day kinematical and chemical state. Because stars move away from their birth sites, the current dynamical information alone is not sufficient for this task. The chemical composition of stellar atmospheres, on the other hand, is largely preserved over the stellar lifetime and, together with accurate ages, can be used to recover the birthplaces of stars currently found at the same Galactic radius. In addition to the availability of large stellar samples with accurate 6D kinematics and chemical abundance measurements, this requires detailed modeling with both dynamical and chemical evolution taken into account. An important first step is to understand the variety of dynamical processes that can take place in the Milky Way, including the perturbative effects of both internal (bar and spiral structure) and external (infalling satellites) agents. We discuss here (1) how to constrain the Galactic bar, spiral structure, and merging satellites by their effect on the local and global disc phase-space, (2) the effect of multiple patterns on the disc dynamics, and (3) the importance of radial migration and merger perturbations for the formation of the Galactic thick disc. Finally, we discuss the construction of Milky Way chemo-dynamical models and relate to observations.

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“…• a recent suggestion is that stars on more energetic orbits migrate out from the inner galaxy to form a thick disk at larger radii where the potential gradient is weaker (Schönrich & Binney, 2009) How can we test between these possibilities for thick disk formation? Sales et al (2009) looked at the expected orbital eccentricity distribution for thick disk stars in different formation scenarios.…”

Section: The Formation Of the Thick Diskmentioning

confidence: 99%

Structure and Evolution of the Milky Way

Freeman

2011

Astrophysics and Space Science Proceedings

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This review discusses the structure and evolution of the Milky Way, in the context of opportunities provided by asteroseismology of red giants. The review is structured according to the main Galactic components: the thin disk, thick disk, stellar halo, and the Galactic bar/bulge. The review concludes with an overview of Galactic archaeology and chemical tagging, and a brief account of the upcoming HERMES survey with the AAT. The Thin Disk: Formation and EvolutionHere are some of the issues related to the formation and evolution of the Galactic thin disk:• Building the thin disk: its exponential radial structure, and the role of mergers.• The star formation history: chemical evolution and continued gas accretion.• Evolutionary processes in the disk: disk heating, radial mixing.• The outer disk: chemical properties and chemical gradients.Many of the basic observational constraints on the properties of the Galactic disk are still uncertain. At this time, we do not have reliable information about the star formation history of the disk. We do not know how the metallicity distribution and the stellar velocity dispersions in the disk have evolved with time. One might have expected that these observational questions were well understood by now, but this is not yet so. The basic observational problem is the difficulty of measuring ages for individual stars.The younger stars of the Galactic disk show a clear abundance gradient of about 0.07 dex kpc −1 , outlined nicely by the cepheids (Luck et al., 2006). In the outer disk, for the older stars, the abundance gradient appears to be even stronger: the

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Origin and structure of the Galactic disc(s)

Cited by 316 publications

References 28 publications

Separation of stellar populations by an evolving bar: implications for the bulge of the Milky Way

Separation of stellar populations by an evolving bar: implications for the bulge of the Milky Way

Constraining the Milky Way assembly history with Galactic Archaeology

Structure and Evolution of the Milky Way

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