We study the structure of the inner Milky Way (MW) using the latest data release of the Vista Variables in Via Lactea (VVV) survey. The VVV is a deep near-infrared, multi-colour photometric survey with a coverage of 300 square degrees towards the Bulge/Bar. We use Red Clump (RC) stars to produce a high-resolution dust map of the VVV's field of view. From de-reddened colour-magnitude diagrams we select Red Giant Branch stars to investigate their 3D density distribution within the central 4 kpc. We demonstrate that our best-fit parametric model of the Bulge density provides a good description of the VVV data, with a median percentage residual of 5 % over the fitted region. The strongest of the otherwise low-level residuals are overdensities associated with a low-latitude structure as well as the so-called X-shape previously identified using the split RC. These additional components contribute only ∼ 5% and ∼ 7% respectively to the Bulge mass budget. The best-fit Bulge is "boxy" with an axis ratio of [1:0.44:0.31] and is rotated with respect to the Sun-Galactic Centre line by at least ∼ 20• . We provide an estimate of the total, full sky, mass of the Bulge of M Chabrier Bulge = 2.36 × 10 10 M for a Chabrier initial mass function. We show there exists a strong degeneracy between the viewing angle and the dispersion of the Red Clump (RC) absolute magnitude distribution. The value of the latter is strongly dependent on the assumptions made about the intrinsic luminosity function of the Bulge.

We use a sample of ∼350 RR Lyrae stars with radial velocities and Gaia DR2 proper motions to study orbital properties of the Hercules-Aquila Cloud (HAC) and Virgo Over-density (VOD). We demonstrate that both structures are dominated by stars on highly eccentric orbits, with peri-centres around ∼ 1 kpc and apo-centres between 15 and 25 kpc from the Galactic centre. Given that the stars in the HAC and the VOD occupy very similar regions in the space spanned by integrals of motion, we conclude that these diffuse debris clouds are part of the same accretion event. More precisely, these inner halo sub-structures likely represent two complementary not-fully-mixed portions of an ancient massive merger, also known as the "sausage" event.As demonstrated by the recent re-interpretation of the Monoceros Ring (and the associated sub-structures) and the

The Blanco DECam Bulge Survey (BDBS) imaged more than 200 square degrees of the Southern Galactic bulge using the ugrizY filters of the Dark Energy Camera, and produced point spread function photometry of approximately 250 million unique sources. In this paper, we present details regarding the construction and collation of survey catalogs, and also discuss the adopted calibration and dereddening procedures. Early science results are presented with a particular emphasis on the bulge metallicity distribution function and globular clusters. A key result is the strong correlation (σ ∼ 0.2 dex) between (u − i)o and [Fe/H] for bulge red clump giants. We utilized this relation to find that interior bulge fields may be well described by simple closed box enrichment models, but fields exterior to b ∼−6○ seem to require a secondary metal-poor component. Applying scaled versions of the closed box model to the outer bulge fields is shown to significantly reduce the strengths of any additional metal-poor components when compared to Gaussian mixture models. Additional results include: a confirmation that the u-band splits the sub-giant branch in M 22 as a function of metallicity, the detection of possible extra-tidal stars along the orbits of M 22 and FSR 1758, and additional evidence that NGC 6569 may have a small but discrete He spread, as evidenced by red clump luminosity variations in the reddest bands. We do not confirm previous claims that FSR 1758 is part of a larger extended structure.

A wealth of recent studies have shown that the LMC is likely massive, with a halo mass >1011M⊙. One consequence of having such a nearby and massive neighbour is that the inner Milky Way is expected to be accelerated with respect to our Galaxy’s outskirts (beyond ∼30 kpc). In this work we compile a sample of ∼500 stars with radial velocities in the distant stellar halo, rGC > 50 kpc, to test this hypothesis. These stars span a large fraction of the sky and thus give a global view of the stellar halo. We find that stars in the Southern hemisphere are on average blueshifted, while stars in the North are redshifted, consistent with the expected, mostly downwards acceleration of the inner halo due to the LMC. We compare these results with simulations and find the signal is consistent with the infall of a 1.5 × 1011M⊙ LMC. We cross-match our stellar sample with Gaia DR2 and find that the mean proper motions are not yet precise enough to discern the LMC’s effect. Our results show that the Milky Way is significantly out of equilibrium and that the LMC has a substantial effect on our Galaxy.