Pre-cursor LSST Galactic Archeology with Subaru/HSC

Beth Willman

I'll present first results and predictions for our Subaru/HSC observational program to comprehensively map LMC stellar mass galaxies at distances of ~2- 4 Mpc. The MADCASH (Magellanic Analog Dwarf Companions And Stellar Halos) survey will deliver the first census of the dwarf satellite populations and stellar halo properties within LMC-like environments in the Local Volume. These will inform our understanding of the recent Dark Energy Survey discoveries of dwarf satellites tentatively affiliated with the LMC/SMC system. We will detail our discovery of the faintest known dwarf galaxy satellite of an LMC stellar-mass host beyond the Local Group, based on deep Subaru/HSC imaging reaching ~2 magnitudes below its TRGB. We will summarize the survey results and status to date, highlighting some challenges encountered and lessons learned as we process the data for this program through a prototype LSST pipeline. Our program will examine whether LMC stellar mass dwarfs have extended stellar halos, allowing us to investigate the relative contributions of in-situ stars vs. merger debris to their stellar populations and halo density profiles.