NOAO >   Observing Info >   Approved Programs >   2017A-0210

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Program Information for 2017A-0210


PI: Alistair Walker, CTIO, awalker@ctio.noao.edu
Address: Casilla 603, La Serena Chile

CoI: Kathy Vivas, CTIO
CoI: Matteo Monelli, Instituto de Astrofisica de Canarias
CoI: Carme Gallart, Instituto de Astrofisica de Canarias
CoI: David Nidever, NOAO
CoI: Knut Olsen, NOAO

Title: The large but very diffuse Milky Way satellite galaxy Crater II: Stellar Populations

Abstract: We propose to investigate the stellar population content of the recently discovered Milky Way satellite Crater II. This galaxy, which is the fourth largest of all the galactic satellites but among the faintest of the "classical" dwarfs, occupies a unique place in the absolute magnitude-size plane with only a possible similar counterpart among the Andromeda satellites. The determination of the star formation history of a galaxy with such extraordinary properties is an important ingredient toward our understanding of galaxy assembly in our neighborhood. Our goal is to obtain time series in g and i passbands of a single DECam pointing that covers all of Crater II for identifying RR Lyrae stars which trace old populations and Anomalous Cepheid stars (if they exist) which can indicate the presence of an intermediate-age population. The RR Lyrae stars will also provide an accurate distance to the system and if present in sufficient numbers may give an indication of its 3D structure and spread in metallicity. The individual images of the time series will be combined to obtain a deep color-magnitude diagram reaching below the main sequence turnoff, which will allow us to fully characterize the evolutionary status of Crater II. In particular, we will explore the existence of stellar populations with a range of ages and re-derive the structural parameters of the galaxy.

Program Type: Standard/Galactic

Scheduled Nights:
Run 1 (2017A):  CT-4m/DECam -- 3n on Mar 19 - Mar 21 2017


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