We have derived absolute proper motions of the entire Galactic bulge region from VIRAC and Gaia. We present these as both integrated on-sky maps and, after isolating standard candle red clump (RC) stars, as a function of distance using RC magnitude as a proxy. These data provide a new global, 3-dimensional view of the Milky Way barred bulge kinematics. We find a gradient in the mean longitudinal proper motion, <µ l >, between the different sides of the bar, which is sensitive to the bar pattern speed. The split RC has distinct proper motions and is colder than other stars at similar distance. The proper motion correlation map has a quadrupole pattern in all magnitude slices showing no evidence for a separate, more axisymmetric inner bulge component. The line-of-sight integrated kinematic maps show a high central velocity dispersion surrounded by a more asymmetric dispersion profile. σ µ l /σ µ b is smallest, ∼1.1, near the minor axis and reaches ∼1.4 near the disc plane. The integrated <µ b > pattern signals a superposition of bar rotation and internal streaming motion, with the near part shrinking in latitude and the far part expanding. To understand and interpret these remarkable data, we compare to a made-to-measure barred dynamical model, folding in the VIRAC selection function to construct mock maps. We find that our model of the barred bulge, with a pattern speed of 37.5 km s −1 kpc −1 , is able to reproduce all observed features impressively well. Dynamical models like this will be key to unlocking the full potential of these data.There is still an ongoing debate as to whether there exists a secondary classical bulge component in the central parts of the bulge (Shen et al. 2010;Rojas-Arriagada et al. 2017;Di Matteo et al. 2015;Barbuy et al. 2018). With modern stellar surveys, the MW bulge and bar can be studied at great depth, rapidly making the MW a prototypical system for understanding the formation and evolution of similar galaxies.A prominent feature of the barred bulge is the split red clump (RC) which was first reported by Nataf et al. (2010); McWilliam & Zoccali (2010) using OGLE-III photometry and 2MASS data respectively. They showed that this phenomenon occurs close to the MW minor axis at latitudes of |b| 5 • . From these analyses it was suggested that the split RC could be the result of a funnel shaped component in the bulge which is now commonly referred to as X-shaped.

Gas morphology and kinematics in the Milky Way contain key information for understanding the formation and evolution of our Galaxy. We present hydrodynamical simulations based on realistic barred Milky Way potentials constrained by recent observations. Our model can reproduce most features in the observed longitude–velocity diagram, including the Central Molecular Zone, the Near and Far 3 kpc arms, the Molecular Ring, and the spiral arm tangents. It can also explain the noncircular motions of masers from the recent BeSSeL2 survey. The central gas kinematics are consistent with a mass of 6.9 × 108 M ⊙ in the Nuclear Stellar Disk. Our model predicts the formation of an elliptical gaseous ring surrounding the bar, which is composed of the 3 kpc arms, the Norma arm, and the bar-spiral interfaces. This ring is similar to those “inner” rings in some Milky Way analogs with a boxy/peanut-shaped bulge (e.g., NGC 4565 and NGC 5746). The kinematics of gas near the solar neighborhood are governed by the Local arm. The bar pattern speed constrained by our gas model is 37.5–40 km s−1 kpc−1, corresponding to a corotation radius of R CR = 6.0–6.4 kpc. The rotation curve of our model rises gently within the central ∼ 5 kpc, significantly less steep than those predicted by some recent zoom-in cosmological simulations.

Aims. Spectroscopic surveys have by now collectively observed tens of thousands of stars in the bulge of our Galaxy. However, each of these surveys had unique observing and data processing strategies that led to distinct stellar parameter and abundance scales. Because of this, stellar samples from different surveys cannot be directly combined. Methods. Here we use the data-driven method, The Cannon, to bring 21 000 stars from the ARGOS bulge survey, including 10 000 red clump stars, onto the parameter and abundance scales of the cross-Galactic survey, APOGEE, obtaining rms precisions of 0.10 dex, 0.07 dex, 74 K, and 0.18 dex for [Fe/H], [Mg/Fe], Teff, and log(g), respectively. The re-calibrated ARGOS survey – which we refer to as the A2A survey – is combined with the APOGEE survey to investigate the abundance structure of the Galactic bulge. Results. We find X-shaped [Fe/H] and [Mg/Fe] distributions in the bulge that are more pinched than the bulge density, a signature of its disk origin. The mean abundance along the major axis of the bar varies such that the stars are more [Fe/H]-poor and [Mg/Fe]-rich near the Galactic centre than in the outer bulge and the long bar region. The vertical [Fe/H] and [Mg/Fe] gradients vary between the inner bulge and the long bar, with the inner bulge showing a flattening near the plane that is absent in the long bar. The [Fe/H] − [Mg/Fe] distribution shows two main maxima, an ‘[Fe/H]-poor [Mg/Fe]- rich’ maximum and an ‘[Fe/H]-rich [Mg/Fe]-poor’ maximum, that vary in strength with position in the bulge. In particular, the outer long bar close to the Galactic plane is dominated by super-solar [Fe/H], [Mg/Fe]-normal stars. Stars composing the [Fe/H]-rich maximum show little kinematic dependence on [Fe/H], but for lower [Fe/H] the rotation and dispersion of the bulge increase slowly. Stars with [Fe/H] < −1 dex have a very different kinematic structure than stars with higher [Fe/H]. Conclusions. Comparing with recent models for the Galactic boxy-peanut bulge, the abundance gradients and distribution, and the relation between [Fe/H] and kinematics suggests that the stars comprising each maximum have separate disk origins with the ‘[Fe/H]-poor [Mg/Fe]-rich’ stars originating from a thicker disk than the ‘[Fe/H]-rich [Mg/Fe]-poor’ stars.

We compare distance resolved, absolute proper motions in the Milky Way bar/bulge region to a grid of made-to-measure dynamical models with well defined pattern speeds. The data are obtained by combining the relative VVV Infrared Astrometric Catalog v1 proper motions with the Gaia DR2 absolute reference frame. We undertake a comprehensive analysis of the various errors in our comparison, from both the data and the models, and allow for additional, unknown, contributions by using an outlier-tolerant likelihood function to evaluate the best fitting model. We quantify systematic effects such as the region of data included in the comparison, the possible overlap from spiral arms, and the choice of synthetic luminosity function and bar angle used to predict the data from the models. Resulting variations in the best-fit parameters are included in their final errors. We thus measure the bar pattern speed to be Ωb = 33.29 ± 1.81  km s−1 kpc−1 and the azimuthal solar velocity to be Vφ, ⊙ = 251.31 ± 1.95  km s−1. These values, when combined with recent measurements of the Galactic rotation curve, yield the distance of corotation, 6.5 &lt; RCR [kpc] &lt; 7.5, the outer Lindblad resonance (OLR), 10.7 &lt; ROLR [kpc] &lt; 12.4, and the higher order, m = 4, OLR, $8.7 &lt; R_\mathrm{OLR_4}\, [\mathrm{ kpc }] &lt; 10.0$. The measured pattern speed provides strong evidence for the ”long-slow” bar scenario.

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