NOAO >   Observing Info >   Approved Programs >   2014B-0304

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Proposal Information for 2014B-0304


PI: Rachael L. Beaton, University of Virginia, rlb9n@virginia.edu
Address: Astronomy Department, 530 McCormick Road, Charlottesville, Virginia 22901, USA

CoI: Steven R. Majewski, University of Virginia
CoI: Puragra Guhathakurta, UC-Santa Cruz
CoI: Katherine Hamren, UC-Santa Cruz

Title: Robust Distances to Twenty M31 Satellites

Abstract: The dwarf satellites of the Milky Way (MW) and of Andromeda (M31) are powerful probes of the astro-physical processes of galaxy formation and evolution in the (Lambda)-CDM paradigm. However, the majority are intrinsically low-lumonsity objects that pose challenges for standard distance estimating techniques like the tip of the red giant branch (TRGB), and young, bright Cepheid variables. Without accurate distances, we cannot accurately assess linear scales and morphologies or interpret spectroscopic metallicities, commonly tied to an absolute magnitude scale. We propose to properly leverage our current knowledge of the M31 dwarf satellite population by placing it into a robust 3- dimensional context and providing a deep probe into their stellar content. First, we will identify and characterize bright (M_V~0.5 to -1.5), short-period (P_AC~ 0.5 to 2.5 day) variables known as Anomalous Cepheids in each of twenty galaxies through time resolved photometry, building on existing optical data from the Specroscopic and Photometric Landscape of the Stellar Halo (SPLASH) survey to break aliasing effects in period estimation. Combined with NIR imaging from the NOAO Survey Program M31-AGES, we will be able to derive distances and masses for each star from the more precise, NIR period-luminosity (PL) and period-luminosity-color (PLC) relations. Second, we will stack the time series images to produce a deep color-magnitude diagram for each galaxy (V~27, I~25). % sufficient to reach the horizontal branch. The stacked optical data will also reveal, the horizontal branch, which provides a second distance estimate, as well as invaluable insight into the stellar content and star formation history of each galaxy.


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