2022ApJ...932L..16D -
Astrophys. J., 932, L16-L16 (2022/June-3)
The Local Stellar Halo is Not Dominated by a Single Radial Merger Event.
DONLON II T., NEWBERG H.J., KIM B. and LEPINE S.
Abstract (from CDS):
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, nonrotating RME component we name Nereus is identified with [Fe/H] = -2.1 and has similar energy to the VRM. We identify a possible third RME, which we name Cronus, that is corotating 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 σv ∼ 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 that comprise the "Gaia Sausage" velocity structure are a combination of the components identified in this work.
Abstract Copyright:
© 2022. The Author(s). Published by the American Astronomical Society.
Journal keyword(s):
Milky Way Galaxy - Galaxy mergers - Galaxy accretion - Milky Way dynamics
Errata:
erratum vol. 941, art. L21 (2022)
Simbad objects:
4
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