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SDSS-IV MaNGA: environmental dependence of the Mgb/⟨Fe⟩-σ* relation for nearby galaxies

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We use a sample of ~3000 galaxies from the MaNGA MPL-7 internal data release to study the α abundance distribution within low-redshift galaxies. We use the Lick index ratio Mgb/⟨Fe⟩ as an αabundance indicator to study relationships between the α abundance distribution and galaxy properties such as effective stellar velocity dispersion within 0.3 effective radii (σ*), galaxy environment, and dark matter halo formation time (zf ). We find that (1) all galaxies show a tight correlation between Mgb/⟨Fe⟩ and σ*;(2) "old" (Hβ < 3) low-σ* galaxies in high local density environment and inner regions within galaxy groups are enhanced in Mgb/⟨Fe⟩, while "young" (Hβ > 3) galaxies and high-mass galaxies show no or less environmental dependence; (3) "old" galaxies with high-zf  show enhanced Mgb⟨Fe⟩/ over low- and medium-zf ; and (4) Mgb/⟨Fe⟩ gradients are close to zero and show dependence on σ* but no obvious dependence on the environment or zf . Our study indicates that stellar velocity dispersion or galaxy mass is the main parameter driving the Mgb/⟨Fe⟩ enhancement, although environments appear to have modest effects, particularly for low- and medium-mass galaxies.
Original languageEnglish
Article number63
Number of pages15
JournalAstrophysical Journal
Volume873
Issue number1
DOIs
Publication statusPublished - 5 Mar 2019

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