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Abundance gradients of the Large Magellanic Cloud using APOGEE

Presentation #156.03 in the session “Dwarf and Irregular Galaxies”.

Published onJan 11, 2021
Abundance gradients of the Large Magellanic Cloud using APOGEE

Dwarf galaxies are among the most abundant objects in the Universe, but they are notably difficult to study as they are intrinsically faint and often distant.  Unlike most dwarf galaxies, the Magellanic Clouds are close enough and bright enough to resolve individual stars making them the perfect laboratories to study the evolution of dwarf galaxies. The dual-hemisphere and high-resolution Apache Point Observatory Galactic Evolution Experiment (APOGEE) provides accurate radial velocities and chemical abundances, making it the perfect tool to study galactic evolution in the local neighborhood. An important component of APOGEE is APOGEE-2 South, which surveyed ~5000 RGB stars in the Clouds. The survey has broad azimuthal and radial coverage out to 10 deg in the Large Magellanic Cloud (LMC), and therefore, the data from APOGEE is an ideal dataset to study galactic evolution in the context of merging dwarf galaxies. For this work, the accurate LMC SMASH red clump distance map from Choi et al. (2018a) and stellar isochrones were used to calculate star-by-star ages which in turn were used with APOGEE DR16 stellar parameters to calculate LMC radial abundance trends. I present the results of LMC radial-abundance-age trends and spatial abundance gradients. The iron peak elements generally exhibit more negative gradients compared to other groups of elements such as the alpha elements. In particular, the [Fe/H] gradients become more steeply negative over time suggesting a buildup of stars in the center of the galaxy over time until ~2 Gyr ago. The alpha element gradients are fairly uniform over all ages except for the youngest stars, which show a similar, albeit smaller, gradient inflection to iron. In fact, many of the elements show an inflection at the same time and point to a recent starburst in the LMC initiated by an interaction with the SMC described in Nidever et al. (2020) as the cause.

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