The geometry and distance of the Magellanic Clouds from Cepheid variables

Period, luminosity and colour data on LMC and SMC Cepheids are analysed. A geometrical model for the LMC and the SMC is presented based on the Cepheids. The distance modulus of each Cloud is redetermined and its dependence upon the assumed abundance deficiency in the Clouds is made explicit. New, independent abundances are inferred based on the Cepheids alone, and are found to agree well with the known H II region abundance deficiencies. The luminosity laws in both galaxies, suitably corrected for abundance, are mutually consistent, enabling a ‘universal’ PLC and PL relation to be obtained which incorporates all the photoelectric data. Finally, it is argued that the 21 cm data of Mathewson & Ford are consistent with our view of the SMC as a two-armed galaxy, showing its central bar to us edge on, with a mass of material pulled out of its centre towards the SW seen in projection against the far arm. That the SMC consists of two separated fragments over much of its angular extent seems less plausible.