Morphology of the Small Magellanic Cloud using multiwavelength photometry of classical Cepheids

Abstract

ABSTRACT This is the second of a series related to the study of geometry of the Magellanic Clouds based on multiwavelength photometry of classical Cepheids. In this paper we determine the geometrical and viewing angle parameters of the Small Magellanic Cloud (SMC) using the Leavitt law for classical Cepheids with/without a break in the law at a certain period as reported in the literature. The study utilizes photometric data for more than 3400 common classical Cepheids (Fundamental (FU) and First overtone (FO)) in optical (V, I), near-infrared (Y, J, Ks) and mid-infrared ([3.6] and [4.5] μm) photometric bands. We obtain statistical reddening and distance modulus free from the effect of reddening to each of the individual Cepheids with respect to the mean distance modulus and reddening of the SMC. The reddening maps of the SMC obtained from the analyses with/without breaks in the Leavitt law show good agreement with each other as well as with other maps available in the literature. The Cartesian coordinates of individual stars with respect to the galaxy plane are obtained using the information of equatorial coordinates (α, δ) as well as extinction-free distance measurements. Modelling the observed 3D distribution of the Cepheids as a triaxial ellipsoid, we obtain the geometrical and viewing angle parameters of the SMC. The weighted average yields the following values of parameters for the SMC: the geometrical axes ratios of 1.000 ± 0.001: 1.544 ± 0.002: 9.742 ± 0.030 and the viewing angle parameters having inclination angle i = 3${^{\circ}_{.}}$465 ± 0${^{\circ}_{.}}$030 with respect to the longest axis from the line of sight and position angle of line of nodes (major axis) θlon = 63${^{\circ}_{.}}$086 ± 0${^{\circ}_{.}}$117.