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The Local Stellar Halo is Not Dominated by a Single Radial Merger Event
- Publication Year :
- 2021
-
Abstract
- We use halo dwarf stars with photometrically determined metallicities that are located within 2 kpc of the Sun to identify local halo substructure. The kinematic properties of these stars do not indicate a single, dominant radial merger event (RME). The retrograde Virgo Radial Merger (VRM) component has [Fe/H] = -1.7. A second, non-rotating RME component we name Nereus is identified with [Fe/H] = -2.1 and has similar energy as the VRM. A possible third RME we name Cronus is identified that is co-rotating with the disk, has lower energy than the VRM, and has [Fe/H] = -1.2. We identify the Nyx Stream in the data. In addition to these substructures, we observe metal-poor halo stars ([Fe/H] ~ -2.0 and $\sigma_v$ ~ 180 km s$^{-1}$) and a disk/Splash component with lower rotational velocity than the disk and lower metallicity than typically associated with the Splash. An additional excess of halo stars with low velocity and metallicity of [Fe/H] = -1.5 could be associated with the shell of a lower energy RME or indicate that lower energy halo stars have higher metallicity. Stars which comprise the "Gaia Sausage" velocity structure are a combination of the components identified in this work.
- Subjects :
- Astrophysics - Astrophysics of Galaxies
Subjects
Details
- Database :
- arXiv
- Publication Type :
- Report
- Accession number :
- edsarx.2110.11465
- Document Type :
- Working Paper
- Full Text :
- https://doi.org/10.3847/2041-8213/ac7531