UC Santa Cruz

We present a homogeneous spectroscopic dataset of 22,339 stars in 78 Milky Way dwarf galaxy satellites and globular clusters. All data were taken with the Keck II telescope and Deep Extragalactic Imaging Multiobject Spectrograph (DEIMOS) using the 1200G grating (spectral resolution R ≃ 6000). Based on a uniform data reduction of 411 DEIMOS masks, we present a catalog of individual stellar radial velocities, equivalent-width-based [Fe/H] metallicities, and membership estimates. The Milky Way satellites range from MV = 2 to −14 (M⋆ = 101.5–107.5 M⊙); the majority of individual stars presented in these systems have magnitudes between 17 > r > 22. We additionally present redshifts for 2097 compact background galaxies and QSOs in the same magnitude range. The data were reduced to 1D spectra using PypeIt, which provides near Poisson-statistics-level sky subtraction. Radial velocities were determined via dmost, a forward modeling method first presented here, which combines both synthetic telluric and stellar templates to determine stellar radial velocities. We assess the accuracy and precision our method via comparison to thousands of repeat measurements and literature values. We determine a velocity error floor of 1.1 km s−1 and a Ca ii-triplet-based metallicity error floor of 0.1 dex. We calculate internal velocity dispersions and compare to literature values, demonstrating 20%–50% improved precision over the literature in most cases. In a companion paper, we use our homogeneous catalogs to explore properties of these Milky Way satellites, including previously unpublished measurements in several systems including Boötes II and Draco II. We provide full access to the data catalogs to enable further studies.