The 3D Structure of the Galactic Bulge

Zoccali, M.; Valenti, E.

doi:10.1017/pasa.2015.56

Cited by 44 publications

(31 citation statements)

References 99 publications

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“…16 we present the results for the φ bar = 25 • and 40 • view angles. Similar to the results of Gonzalez et al (2011) and also Zoccali & Valenti (2016), we "observe" bars much more inclined than the assumed bar angle and the bar angle changes between |l| =5-10 • . This is due to the projection effect and the existence of the bulge which was nicely shown, using N -body simulations, by Gerhard & Martinez-Valpuesta (2012).…”

Section: Inner Bar Structuresupporting

confidence: 87%

Modelling the Milky Way as a dry Galaxy

Fujii

Bédorf

Baba

et al. 2018

Monthly Notices of the Royal Astronomical Society

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We construct a model for the Milky Way Galaxy composed of a stellar disc and bulge embedded in a dark-matter halo. All components are modelled as N -body systems with up to 8 billion equal-mass particles and integrated up to an age of 10 Gyr. We find that net angular-momentum of the dark-matter halo with a spin parameter of λ = 0.06 is required to form a relatively short bar (∼ 4 kpc) with a high pattern speed (40-50 km s −1 ). By comparing our model with observations of the Milky Way Galaxy, we conclude that a disc mass of ∼ 3.7 × 10 10 M and an initial bulge scale length and velocity of ∼ 1 kpc and ∼ 300 km s −1 , respectively, fit best to the observations. The disc-to-total mass fraction (f d ) appears to be an important parameter for the evolution of the Galaxy and models with f d ∼ 0.45 are most similar to the Milky Way Galaxy. In addition, we compare the velocity distribution in the solar neighbourhood in our simulations with observations in the Milky Way Galaxy. In our simulations the observed gap in the velocity distribution, which is expected to be caused by the outer Lindblad resonance (the so-called Hercules stream), appears to be a time-dependent structure. The velocity distribution changes on a time scale of 20-30 Myr and therefore it is difficult to estimate the pattern speed of the bar from the shape of the local velocity distribution alone.

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Section: Inner Bar Structuresupporting

confidence: 87%

Modelling the Milky Way as a dry Galaxy

Fujii

Bédorf

Baba

et al. 2018

Monthly Notices of the Royal Astronomical Society

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“…Moreover, one of the simulated halos (Aq-C-5) showed a good match with the spatial, kinematic, and metallicity properties observed in the MW (Zoccali & Valenti 2016). The analysis of the assembly history of the central regions shows that this halo did not accrete satellite galaxies more massive than ∼10…”

Section: The Simulated Aquarius Galaxiesmentioning

confidence: 51%

The Origin of the Milky Way's Halo Age Distribution

Carollo

Tissera

Gudin

et al. 2018

ApJL

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We present an analysis of the radial age gradients for the stellar halos of five Milky Way (MW) mass-sized systems simulated as part of the Aquarius Project. The halos show a diversity of age trends, reflecting their different assembly histories. Four of the simulated halos possess clear negative age gradients, ranging from approximately −7 to −19 Myr kpc −1 , shallower than those determined by recent observational studies of the Milky Way's stellar halo. However, when restricting the analysis to the accreted component alone, all of the stellar halos exhibit a steeper negative age gradient with values ranging from −8 to −32 Myr kpc, closer to those observed in the Galaxy. Two of the accretion-dominated simulated halos show a large concentration of old stars in the center, in agreement with the Ancient Chronographic Sphere reported observationally. The stellar halo that best reproduces the current observed characteristics of the age distributions of the Galaxy is that formed principally by the accretion of small satellite galaxies. Our findings suggest that the hierarchical clustering scenario can reproduce the MW's halo age distribution if the stellar halo was assembled from accretion and the disruption of satellite galaxies with dynamical masses less than ∼10 9.5 M ☉ , and a minimal in situ contribution.

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“…Furthermore, photometric data from Pan-STARRS1 (Chambers et al 2016), 2MASS (Skrutskie et al 2006) and AllWISE (Wright et al 2010), combined with Gaia DR2 (Gaia Collaboration et al 2018) reveal the Galactic bar ⋆ E-mail: jun.baba@nao.ac.jp; babajn2000@gmail.com (JB); d.kawata@ucl.ac.uk (DK) shape in the inner Galactic disc (Anders et al 2019). These observations suggest that the orientation of the major axis of the Galactic bar relative to the axis along the Sun and the Galactic centre is about 25 • (for reviews, Bland-Hawthorn & Gerhard 2016;Zoccali & Valenti 2016). Using kinematic data of the bar/bulge stars, recent studies suggest that the current pattern speed of the Galactic bar is about 40 km s −1 kpc −1 (Portail et al 2017;Bovy et al 2019), as opposed to a fast pattern speed inferred from the kinematics of the solar neighbourhood stars (Dehnen 1999).…”

Section: Introductionmentioning

confidence: 99%

Age dating the Galactic bar with the nuclear stellar disc

Baba

Kawata

2020

Monthly Notices of the Royal Astronomical Society

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We perform an N-body/hydrodynamics simulation of an isolated Milky Way-like galaxy and demonstrate that the formation epoch of the galactic bar can be identified from the age distribution of the nuclear stellar disc (NSD). The bar formation triggers the gas inflow in the bar region, and the gas inflow reaches the central subkpc region followed by an intense star formation for ∼ 1 Gyr. The star formation in the central sub-kpc region forms the thinner, kinematically cooler and rotating NSD component. Consequently, the formation epoch of the galactic bar becomes the oldest limit of the NSD stellar populations, which tells us the formation epoch of the bar. We also discuss that a challenge to measure the age distribution of the NSD in the Milky Way is contamination from the other stellar components, such as a classical bulge component, whose contamination may not be negligible in the central region. We demonstrate that transverse velocities of tracer stars, which will be measured by the near-infrared space astrometry mission, JASMINE, are crucial to kinematically distinguish the NSD from the other stellar component.

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The 3D Structure of the Galactic Bulge

Cited by 44 publications

References 99 publications

Modelling the Milky Way as a dry Galaxy

Modelling the Milky Way as a dry Galaxy

The Origin of the Milky Way's Halo Age Distribution

Age dating the Galactic bar with the nuclear stellar disc

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