| Abstract | New JHK photometry has been obtained for Cepheid variables in the LMC and SMC and has been merged with the existing data of Laney and Stobie (1986a). The total data base comprises 494 JHK observations of 65 LMC Cepheids and 451 JHK observations of 94 SMC Cepheids. Intensity-weighted mean magnitudes have been derived for 57 LMC and 91 SMC Cepheids. From these mean magnitudes, period-luminosity and period-color relations have been determined, and true distance moduli of 18.57 ± 0.05 and 18.93 ± 0.05 mag are found for the LMC and SMC, respectively. The line-of-sight distribution of Cepheids in the LMC and SMC has been investigated using residuals from the H P-L and P-L-C relations. An inclination of 37° ± 16° has been found for the LMC using a planar model. A different approach has been adopted for analysis of the SMC photometry because the structure of the galaxy is clearly not planar. It is found that an additional 0.12 mag dispersion (corresponding to 3.3 kpc in distance) is required to account for the observed width of the H P-L-C relation when compared with that of the LMC. It is concluded that the SMC is not extended beyond its tidal radius unless the mass of the Galaxy is significantly greater than 1012 Msun. Finally, the differences between our interpretation of infrared photometry of Magellanic Cloud Cepheids and that of Mathewson, Ford, and Visvanathan (1986) are discussed. We show that the extreme distances derived in the latter study are probably the result of an inconsistent correction to mean magnitude, the assumption of zero intrinsic width for the P-L relation, and sample inhomogeneity. |
