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Outer Limits Survey


The Outer Limits Survey (OLS) is designed to detect, map, and characterize the extended structure of the Large and Small Magellanic Clouds (LMC and SMC). The survey consists of deep CTIO 4-m Mosaic2 images of 55 0 6 × 0 6 fields distributed at distances up to 20° from the Clouds, with 10 fields at larger distances representing controls for contamination by Galactic foreground stars and background galaxies. The field locations probe the outer structure of both the LMC and SMC, as well as exploring areas defined by the Magellanic Stream, the Leading Arm, and the LMC orbit as recently measured from its proper motion. The images were taken with C, M, R, I, and DDO51 filters on the CTIO Blanco 4 m telescope and Mosaic2 camera, with supporting calibration observations taken at the CTIO 0.9 m telescope. The CRI images reach depths below the oldest main-sequence (MS) turnoffs at the distance of the Clouds, thus yielding numerous probes of structure combined with good ability to measure stellar ages and metallicities. The M and DDO51 images allow for discrimination of LMC and SMC giant stars from foreground dwarfs, allowing one to use giants as additional probes of Cloud structure and populations. From photometry of eight fields located at radii of 7°-19° north of the LMC bar, MS stars associated with the LMC are found out to 16° from the LMC center, while the much rarer giants can be convincingly detected out to 11°.

OLS at a Glance

PI(s) Abhijit Saha
Proposal ID 2006B-0013
Years of Observation 2006-2009
Sample: 11 Fields in the outskirts of the LMC and SMC
Bands C, M, R, I, DDO51
Median Depth (5σ) (C, M, R, I, DDO51) = (26.0, 24.9, 25.2, 24.3, 24.7)
Median Seeing (C, M, R, I, DDO51) = (1.0, 1.1, 0.9, 0.9, 1.0) arcsec
Number of images 144 (11 fields, each with 2 filters in 2 depths plus 3 filters with 3 depths)