Geometry of the Large Magellanic Cloud Disk: Results from MACHO and the Two Micron All Sky Survey
Jan, 2004
17 pages
Published in:
- Astrophys.J. 601 (2004) 260-276
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Abstract: (IOP)
We present a detailed study of the viewing angles and geometry of the inner LMC (ρ4°) based on a sample of more than 2000 MACHO Cepheids with complete {VR}KClight curves and single-phase Two Micron All Sky Survey (2MASS)JHKsobservations. The sample is considerably larger than any previously studied subset of LMC Cepheids and has an improved areal coverage. Single-epoch random-phase 2MASS photometry is corrected using MACHOVlight curves to derive meanJHKsmagnitudes. We analyze the resulting period-luminosity relations inVRJHKsto recover statistical reddening and distance to each individual Cepheid, with respect to the mean distance modulus and reddening of the LMC. By fitting a plane solution to the derived individual distance moduli, the values of LMC viewing angles are obtained: position angle θ = 1510 ± 24, inclinationi= 307 ± 11. In the so-called ring analysis, we find a strong dependence of the derived viewing angles on the adopted center of the LMC, which we interpret as being due to deviations from planar geometry. Analysis of residuals from the plane fit indicates the presence of a symmetric warp in the LMC disk and the bar elevated above the disk plane. Nonplanar geometry of the inner LMC explains a broad range for values ofiand θ in the literature and suggests caution when deriving viewing angles from inner LMC data.References(0)
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