Magellan/M2FS and MMT/Hectochelle Spectroscopy of Dwarf Galaxies and Faint Star Clusters within the Galactic Halo

Abstract: We present spectroscopic data for 16369 stellar targets within and/or toward 38 dwarf spheroidal galaxies and faint star clusters within the Milky Way halo environment. All spectra come from observations with the multi-object, fiber-fed echelle spectrographs M2FS at the Magellan/Clay telescope or Hectochelle at the MMT, reaching a typical limiting magnitude G < 21. Data products include processed spectra from all observations and catalogs listing estimates -- derived from template model fitting -- of line-of-sight velocity (median uncertainty 1.1 km/s) effective temperature (234 K), (base10 logarithm of) surface gravity (0.52 dex in cgs units), Fe/H and Mg/Fe abundance ratios. The sample contains multi-epoch measurements for 3720 sources, with up to 15 epochs per source, enabling studies of intrinsic spectroscopic variability. The sample contains 6078 likely red giant stars (based on surface gravity), and 4494 likely members (based on line-of-sight velocity and Gaia-measured proper motion) of the target systems. The number of member stars per individual target system ranges from a few, for the faintest systems, to ~ 850 for the most luminous. For most systems, our new samples extend over wider fields than have previously been observed; of the likely members in our samples, 823 lie beyond twice the projected halflight radius of their host system, and 42 lie beyond 5 Rhalf.