This is about my 2nd first-author paper which is focused on studying the origins of old, metal-poor stars with prograde orbits located in the disks of Milky Way-like galaxies using the cosmological zoom-in baryonic simulations from the FIRE project. Read a low-level explanation of the results on the UC Davis College of Letters and Science research blog here! Here is the link to ADS.
Here are a few key takeaways from my paper:
Metal-poor ([Fe/H] < -2.5) stars located within the disk (R = [4, 12] kpc, |Z| < 3 kpc) of MW-like galaxies preferentially orbit in a prograde manner, and this is a common feature in 11 out of the 12 simulated galaxies in our sample. Here is an example in one galaxy, where the boxes show the prograde and retrograde selection windows.
This prograde preference of metal-poor stars does not depend on stellar metallicity. We see this prograde bias across -4 < [Fe/H] < -0.
The largest contribution of these stars is due to a single massive, gas-rich satellite galaxy merger that occurred roughly 7 Gyr ago. The rest of these stars were brought in from lessor contributing galaxy mergers as well as early in-situ formation. Below is an example in one galaxy where the arrows show when the three most massive mergers that contributed these metal-poor, prograde stars (decreasing mass with decreasing opacity in the arrows). The angle shows the relative angular momentum of the merging satellite orbit and the host disk. This shows that the merger helped set the orientation of the disk!
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