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APOGEE’s seven little dwarfs

Presentation #108.03 in the session SDSS-IVever: Continuing Science from SDSS-IV Surveys.

Published onJun 19, 2024
APOGEE’s seven little dwarfs

In addition to the science requirements related to the Milky Way, The Apache Point Observatory Galactic Evolution Experiment (APOGEE) also targeted stars in nearby galaxies as part of its core science goals. This has resulted in publications on the more massive dwarf galaxies: Sagittarius, Fornax and the Large and Small Magellanic Clouds. In this work we follow-up with analysis of stars from the Carina, Sextans, Sculptor, Draco, Ursa Minor, Bootes 1 and Fornax (to have some overlap with the previous studies). While intrinsically very luminous the distance of these galaxies have largely restricted detailed high resolution abundance work to 8-m class telescopes. For APOGEE to be competitive a large number of individual exposures were summed together to produce combined spectra with typical S/N far less than most Galactic APOGEE spectra. APOGEE DR17 abundance methodology ASPCAP always produces abundances for stars with no error flags even if those lines would be undetectable. At lower S/N this becomes a more significant issue, and to address this we create a formalism for determining upper limits based on probable line detectability as a function of S/N, Teff and elemental abundance on a star-by-star basis. Using this formalism we present the results of the Apache Point Observatory extra-Galactic Evolution Experiment (APOeGEE) for 49 Carina, 36 Sextans, 149 Sculptor, 40 Draco, 43 Ursa Minor, 4 Bootes 1, and 207 Fornax giants in Fe, Mg, Si, Al, O, C, N, and to a lesser extent, Ca, Mn, Ni, Ce, and Cr.

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