2004/01/20 by S. Nikolaev, A. J. Drake, S. Keller +5 · 3 citations
Physics and Astronomy · Engineering · #Stellar, planetary, and galactic studies #Astrophysics and Star Formation Studies #Astronomical Observations and Instrumentation
paper · pdf · doi:10.1086/380439
openalex publication_date 2004/01/20 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31
We present a detailed study of the viewing angles and geometry of the inner LMC (ρ ≲ 4°) based on a sample of more than 2000 MACHO Cepheids with complete VR KC light curves and single-phase Two Micron All Sky Survey (2MASS) JHK s observations. 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 MACHO V light curves to derive mean JHK s magnitudes. We analyze the resulting period-luminosity relations in VRJHK s to 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 = 151 0 ± 2 4, inclination i = 30 7 ± 1 1. 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 of i and θ in the literature and suggests caution when deriving viewing angles from inner LMC data.