Measuring Dwarf Galaxy Intrinsic Abundance Scatter with Mid-resolution Spectroscopic Surveys: Calibrating APOGEE Abundance Errors

The first generations of stars left their chemical fingerprints on metal-poor stars in the Milky Way and its
surrounding dwarf galaxies. While instantaneous and homogeneous enrichment implies that groups of co-natal
stars should have the same element abundances, small amplitudes of abundance scatter are seen at fixed [Fe/H].
Measurements of intrinsic abundance scatter have been made with small, high-resolution spectroscopic datasets
where measurement uncertainty is small compared to this scatter. In this work, we present a method to use mid
resolution survey data, which has larger errors, to make this measurement. Using APOGEE DR17, we calculate
the intrinsic scatter of Al, O, Mg, Si, Ti, Ni, and Mn relative to Fe for 333 metal-poor stars across 6 classical
dwarf galaxies around the Milky Way, and 1604 stars across 19 globular clusters. We first calibrate the reported
abundance errors in bins of signal-to-noise and [Fe/H] using a high-fidelity halo dataset. We then apply these
calibrated errors to the APOGEE data, and find small amplitudes of average intrinsic abundance scatter in dwarf
galaxies ranging from 0.032 − 0.14 dex with a median value of 0.043 dex. For the globular clusters, we find
intrinsic scatters ranging from 0.018 − 0.21 dex, with particularly high scatter for Al and O. Our measurements
of intrinsic abundance scatter place important upper limits on the intrinsic scatter in these systems, as well as
constraints on their underlying star formation history and mixing, that we can look to simulations to interpret