2024/12/04 by Shuo Xu, Xu, Shuo, Song Huang +11 · 1 citation
Engineering · Physics and Astronomy · #Astronomical Observations and Instrumentation #Astronomy and Astrophysical Research #Astrophysics of Galaxies (astro-ph.GA) #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #Stellar, planetary, and galactic studies
paper · pdf · doi:10.48550/arxiv.2412.03406
openalex publication_date 2024/12/04 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/01
Recent observations suggest that the extended stellar halos of low-redshift massive galaxies are tightly connected to the assembly of their dark matter halos. In this paper, we use the Illustris, IllustrisTNG100, and IllustrisTNG300 simulations to compare how different stellar aperture masses trace halo mass. For massive central galaxies (M_⋆≥ 1011.2M_\odot), we find that a 2D outskirt stellar mass measured between 50 to 100 kpc (M⋆,[50,100]) consistently outperforms other aperture-based stellar masses. We further show that M⋆,[50,100] correlates better with halo mass than the total amount of accreted stars (the ex situ mass), which suggests that not all accreted stars connect to halo assembly equally. While the galaxy formation recipes are different between Illustris and IllustrisTNG100, the two simulations yield consistent ex situ outskirt fractions for massive galaxies (about 70% in M⋆,[50,100]). These results demonstrate the potential of using the outskirt stellar mass to deepen our understanding of galaxy-halo connection in massive dark matter halos and trace dark matter halos better.