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تسجيل مستخدم جديدElemental Abundances in M31: Properties of the Inner Stellar Halo
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We present measurements of [Fe/H] and [$alpha$/Fe] for 128 individual red giant branch stars (RGB) in the stellar halo of M31, including its Giant Stellar Stream (GSS), obtained using spectral synthesis of low- and medium-resolution Keck/DEIMOS spectroscopy ($R sim 3000$ and 6000, respectively). We observed four fields in M31s stellar halo (at projected radii of 9, 18, 23, and 31 kpc), as well as two fields in the GSS (at 33 kpc). In combination with existing literature measurements, we have increased the sample size of [Fe/H] and [$alpha$/Fe] measurements from 101 to a total of 229 individual M31 RGB stars. From this sample, we investigate the chemical abundance properties of M31s inner halo, finding $langle$[Fe/H]$rangle$ = $-$1.08 $pm$ 0.04 and $langle$[$alpha$/Fe]$rangle$ = 0.40 $pm$ 0.03. Between 8--34 kpc, the inner halo has a steep [Fe/H] gradient ($-$0.025 $pm$ 0.002 dex kpc$^{-1}$) and negligible [$alpha$/Fe] gradient, where substructure in the inner halo is systematically more metal-rich than the smooth component of the halo at a given projected distance. Although the chemical abundances of the inner stellar halo are largely inconsistent with that of present-day dwarf spheroidal (dSph) satellite galaxies of M31, we identified 22 RGB stars kinematically associated with the smooth component of the stellar halo that have chemical abundance patterns similar to M31 dSphs. We discuss formation scenarios for M31s halo, concluding that these dSph-like stars may have been accreted from galaxies of similar stellar mass and star formation history, or of higher stellar mass and similar star formation efficiency.
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We measured [Fe/H] and [$alpha$/Fe] using spectral synthesis of low-resolution stellar spectroscopy for 70 individual red giant branch stars across four fields spanning the outer disk, Giant Stellar Stream (GSS), and inner halo of M31. Fields at M31-
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Measurements of [Fe/H] and [$alpha$/Fe] can probe the minor merging history of a galaxy, providing a direct way to test the hierarchical assembly paradigm. While measurements of [$alpha$/Fe] have been made in the stellar halo of the Milky Way, little
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We analyze existing measurements of [Fe/H] and [$alpha$/Fe] for individual red giant branch (RGB) stars in the Giant Stellar Stream (GSS) of M31 to determine whether spatial abundance gradients are present. These measurements were obtained from low-
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