News and Highlights

The Milky Way Inner Ring 
With the advent of Gaia which provides 6D phase space information, we can now obtain the orbits of many inner Milky Way stars in addition to their chemical and age information. We used APOGEE DR16 orbits integrated in a state of the art potential that was fit to multiple bulge data sets to build detailed orbital density, metallicity, and age maps. We find that a significant amount of APOGEE orbits trace a vertically thin, radially thick elongated ring between 4 and 6 kpc from the Galactic centre.

Wylie, S. M., Clarke, J. P., Gerhard, O., 2022, A&A, 659, A80 more
The Milky Way Bar and Bulge in Proper Motions 
The Galactic bar and bulge dominates the mass distribution in the centre of the Milky Way’s disk. It has been known for a long time that the bar rotates but the precise speed is still hotly debated. We measure the bar pattern speed, and the tangential velocity of the sun, by comparing proper motion data in the Galactic bulge to a series of models which have been constructed with known pattern speeds.

Clarke, J. P., Gerhard, O. 2022, MNRAS, 512, 2171 more
Stellar Halos: Accretion, Merger History, and Dark Halo Connection
Stellar halos of early type galaxies (ETGs) are found to display kinematic changes with radius that reflect changes in their intrinsic structure in both observations (Pulsoni et al. 2018) and simulations (Pulsoni et al. 2020). We analyse simulated ETGs from the IllustrisTNG cosmological simulation to investigate the relation between stellar halo structure and accretion history.

Pulsoni, C., Gerhard, O., Arnaboldi, M., Pillepich, A., Rodrigeuz-Gomez, V., Nelson, D., Hernquist, L., Springel, V., 2021, A&A, 647, A95 more
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