Geometry of the LMC Disk: Results from MACHO and 2MASS

Journal Article · Tue Nov 04 04:00:00 EST 2003 · Astrophysical Journal

OSTI ID:15014422

Nikolaev, S; Drake, A; Keller, S; Cook, K; Dalal, N; Griest, K; Welch, D; Kanbur, S

We have cross-correlated MACHO LMC Cepheids with 2MASS Second Incremental Release Catalog. The resulting database is considerably larger than the set of OGLE Cepheids in the LMC bar, and has significantly better areal coverage, allowing more accurate determination of LMC geometry. Random-phase correction is applied to 2MASS J, H, and Ks magnitudes, using the knowledge of V-band light curve and the ephemeris of 2MASS observations, to produce mean magnitudes. The improvement of phase-corrected PL relations over random-phase PL relations is clearly demonstrated. Reddening is estimated for each star individually, further improving the accuracy of the method. The orientation parameters of the LMC are derived by a Maximum Likelihood approach which solves for viewing angles and PL coefficients simultaneously, providing an unbiased estimation. The results of the analysis are used to place limits on warping of the LMC disk. Implications for the microlensing optical depth are also discussed.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA
• Sponsoring Organization: USDOE
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 15014422
• Report Number(s): UCRL-JRNL-200780
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 601; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

99 GENERAL AND MISCELLANEOUS
ACCURACY
CEPHEIDS
GEOMETRY
ORIENTATION
STARS