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

Debattista, Victor P.; Ness, Melissa; Gonzalez, O. A.; Freeman, K. C.; Zoccali, M.; Minniti, D.

doi:10.1093/mnras/stx947

Cited by 157 publications

(299 citation statements)

References 145 publications

(232 reference statements)

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“…In the inter-arm regions, we find the opposite, and the warm and dynamically hot components contribute to these regions for the majority. Thus, stellar disk populations with initially different random motions are spatially differentiated in the presence of a spiral perturbation, similarly to what has been found for cospatial populations in the Milky Way bar (Debattista et al 2017;Fragkoudi et al 2017).…”

Section: Resultssupporting

confidence: 72%

Stellar metallicity variations across spiral arms in disk galaxies with multiple populations

Khoperskov¹,

Matteo²,

Haywood³

et al. 2018

A&A

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This Letter studies the formation of azimuthal metallicity variations in the disks of spiral galaxies in the absence of initial radial metallicity gradients. Using high-resolution N-body simulations, we model composite stellar discs, made of kinematically cold and hot stellar populations, and study their response to spiral arm perturbations. We find that, as expected, disk populations with different kinematics respond differently to a spiral perturbation, with the tendency for dynamically cooler populations to show a larger fractional contribution to spiral arms than dynamically hotter populations. By assuming a relation between kinematics and metallicity, namely the hotter the population, the more metal-poor it is, this differential response to the spiral arm perturbations naturally leads to azimuthal variations in the mean metallicity of stars in the simulated disk. Thus, azimuthal variations in the mean metallicity of stars across a spiral galaxy are not necessarily a consequence of the reshaping, by radial migration, of an initial radial metallicity gradient. They indeed arise naturally also in stellar disks which have initially only a negative vertical metallicity gradient.

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Section: Resultssupporting

confidence: 72%

Stellar metallicity variations across spiral arms in disk galaxies with multiple populations

Khoperskov¹,

Matteo²,

Haywood³

et al. 2018

A&A

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“…This scenario also reproduces the morphological and kinematic properties of the MW bulge (Athanassoula et al 2017;Debattista et al 2017;Fragkoudi et al 2017). In this framework, the α-enhanced thick disc would have to be overall massive (as asserted by Snaith et al 2015;Haywood et al 2015) and centrally concentrated, i.e.…”

Section: Introductionsupporting

confidence: 62%

What the Milky Way bulge reveals about the initial metallicity gradients in the disc

Fragkoudi

Matteo

Haywood

et al. 2017

A&A

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We use APOGEE DR13 data to examine the metallicity trends in the Milky Way (MW) bulge and we explore their origin by comparing two N-body models of isolated galaxies that develop a bar and a boxy/peanut (b/p) bulge. Both models have been proposed as scenarios for reconciling a disc origin of the MW bulge with a negative vertical metallicity gradient. The first model is a superposition of cospatial, i.e. overlapping, disc populations with different scale heights, kinematics, and metallicities. In this model the thick, metal-poor, and centrally concentrated disc populations contribute significantly to the stellar mass budget in the inner galaxy. The second model is a single disc with an initial steep radial metallicity gradient; this disc is mapped by the bar into the b/p bulge in such a way that the vertical metallicity gradient of the MW bulge is reproduced, as has been shown already in previous works in the literature. However, as we show here, the latter model does not reproduce the positive longitudinal metallicity gradient of the inner disc, nor the metalpoor innermost regions seen in the data. On the other hand, the model with co-spatial thin and thick disc populations reproduces all the aforementioned trends. We therefore see that it is possible to reconcile a (primarily) disc origin for the MW bulge with the observed trends in metallicity by mapping the inner thin and thick discs of the MW into a b/p. For this scenario to reproduce the observations, the α-enhanced, metal-poor, thick disc populations must have a significant mass contribution in the inner regions, as has been suggested for the Milky Way.

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“…Ness et al (2014) also studied the same model to compare the stellar age distribution in the bulge with that of the MW. Lastly, Debattista et al (2017) analysed this model in some detail to demonstrate that all the trends seen in the MW's bulge can be understood as arising from internal evolution via the process of kinematic fractionation. We therefore only provide a brief description of the simulation here, and refer to those papers for further details.…”

Section: The Simulationmentioning

confidence: 99%

Predicted stellar kinematics of a kiloparsec-scale nuclear disc (or ring) in the Milky Way

Debattista

Earp

Ness

et al. 2017

Monthly Notices of the Royal Astronomical Society

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In Debattista et al. (2015), we proposed that a kiloparsec-scale nuclear disc is responsible for the high-velocity secondary peak in the stellar line-of-sight velocity distributions (LOSVDs) seen at positive longitudes in the bulge by the Apache Point Observatory Galactic Evolution Experiment (APOGEE). Here, we make further qualitative but distinctive predictions of the kinematic properties of a nuclear disc, including for the LOSVDs at negative longitudes (which APOGEE-2 will observe) and examine the proper motions throughout the disc. Since a nuclear ring is also able to produce similar high-velocity LOSVD peaks, we present predictions for the proper motion signatures which distinguish between a nuclear disc and a nuclear ring. We also demonstrate that the stars in a nuclear disc, which would be on x2 orbits perpendicular to the bar, can remain on these orbits for a long time and can therefore be old. We show that such (old) nuclear discs of comparable size exist in external galaxies.

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

Cited by 157 publications

References 145 publications

Stellar metallicity variations across spiral arms in disk galaxies with multiple populations

Stellar metallicity variations across spiral arms in disk galaxies with multiple populations

What the Milky Way bulge reveals about the initial metallicity gradients in the disc

Predicted stellar kinematics of a kiloparsec-scale nuclear disc (or ring) in the Milky Way

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