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Paper: Separating M33 Red Giants From Foreground MW Dwarf
Volume: 374, From Stars to Galaxies: Building the Pieces to Build Up the Universe
Page: 283
Authors: Teig, M.; Smecker-Hane, T.; Hood, M.
Abstract: Our goal is to reliably separate foreground MilkyWay dwarfs from M33 red giants via photometry in order to study M33’s stellar populations (thin disk, thick disk and/or halo). Our technique is based on the gravity sensitivity of the MgI triplet lines and MgH absorption band at λ ≈ 5100 Å in stars with F to K spectral types. The strengths of these lines are quantified photometrically using the narrow–band DDO51 filter. The (V − I) vs (DDO51 − V ) colors essentially map onto the theoretical temperature–gravity plane, allowing for clean separation between dwarfs and giants of the same temperature for stars with 1 ≤ (V − I) ≤ 2. Using the the KPNO 4m telescope and MOSAIC camera, we have obtained photometry for four fields in M33, extending to ~ 1°. M33’s distance of 794 kpc (McConnachie et al. 2004) and exponential disk scale length of 1.4 kpc (Ferguson et al. 2006) suggest that the ~ 800 candidate M33 stars we observe beyond 0.67° are probably halo/thick disk stars. Our data are also being used to select targets in our spectroscopic companion work.
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