The structure of the Milky Way's bar outside the bulge

By C. Wegg, O. Gerhard, Matthieu Portail. 2015

247 citations recorded by the source corpus.

While it is incontrovertible that the inner Galaxy contains a bar, its structure near the Galactic plane has remained uncertain, where extinction from intervening dust is greatest. We investigate here the Galactic bar outside the bulge, the long bar, using red clump giant (RCG) stars from UKIDSS, 2MASS, VVV, and GLIMPSE. We match and combine these surveys to investigate a wide area in latitude and longitude, |b|<9deg and |l|<40deg. We find: (1) The bar extends to l~25deg at |b|~5deg from the Galactic plane, and to l~30deg at lower latitudes. (2) The long bar has an angle to the line-of-sight in the range (28-33)deg, consistent with studies of the bulge at |l|<10deg. (3) The scale-height of RCG stars smoothly transitions from the bulge to the thinner long bar. (4) There is evidence for two scale heights in the long bar. We find a ~180pc thin bar component reminiscent of the old thin disk near the sun, and a ~45pc super-thin bar component which exists predominantly towards the bar end. (5) Constructing parametric models for the RC magnitude distributions, we find a bar half length of 5.0+-0.2kpc for the 2-component bar, and 4.6+-0.3kpc for the thin bar component alone. We conclude that the Milky Way contains a central box/peanut bulge which is the vertical extension of a longer, flatter bar, similar as seen in both external galaxies and N-body models.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/f575728ad853f2ecb955177effe10cd5a7142ed4

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In Astronomy and Astrophysics

Citations in the corpus

Constraining the Milky Way assembly history with Galactic Archaeology (2016, unknown): “A drastically different bar pattern speed has recently been suggested by the longer bar half-length measured by Wegg et al. (2015), compared to previous works – rb = 5.0 ± 0.2 kpc, which places the CR at 5-7 kpc.”
CHEMICAL TAGGING CAN WORK: IDENTIFICATION OF STELLAR PHASE-SPACE STRUCTURES PURELY BY CHEMICAL-ABUNDANCE SIMILARITY (2016, background): “The abundance-space group of stars in the disk structure shown in Figure 7 may be associated with a very thin Milky-Way bar component reported previously (Wegg et al. 2015), which is found to exist predominantly toward the end of the bar (at l ≈ 30 deg).”
Dynamical modelling of the galactic bulge and bar: the Milky Way's pattern speed, stellar and dark matter mass distribution (2016, result): “The ratio of corotation radius to bar half-length (Rbar = 5.0±0.2kpc from Wegg et al. 2015) of the Galaxy is found to be R = 1.22± 0.11, in good agreement with what is seen in external disk galaxies.”
The Galaxy in Context: Structural, Kinematic, and Integrated Properties (2016, methodology): “Based on the combined 2MASS, UKIDSS, VVV, and GLIMPSE surveys, Wegg et al. (2015) investigated the long bar in a wide area in latitude and longitude, |b | ≤ 9◦ and |l | ≤ 40◦, using RCG stars and correcting for extinction star by star.”