2024/06/17 by Tetsuya Fukushima, Masashi Chiba, Fukushima, Tetsuya +17 · 1 citation
Physics and Astronomy · Engineering · #Stellar, planetary, and galactic studies #Astronomical Observations and Instrumentation #Astronomy and Astrophysical Research
paper · pdf · doi:10.48550/arxiv.2406.11923
We select blue-horizontal branch stars (BHBs) from the internal data release of the Hyper Suprime-Cam Subaru Strategic Program to reveal the global structure of the Milky Way (MW) stellar halo. The data are distributed over ∼ 1,100~deg2 area in the range of 18.5r\rm b; the statistical difference between these fitting profiles is small. Both profiles are found to show prolate shapes having axial ratios of q=1.47+0.30-0.33 and 1.56+0.34-0.23, respectively. We also find a signature of the so-called "splashback radius" for the candidate BHBs, which can reach as large as r ∼ 575~kpc, although it is still inconclusive owing to rather large distance errors in this faintest end of the sample. Our results suggest that the MW stellar halo consists of the two overlapping components: the \it in situ inner halo showing a relatively steep radial density profile and the \it ex situ outer halo with a shallower profile, being characteristic of a component formed from accretion of small stellar systems.