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We construct a structural model of the Andromeda Galaxy, simultaneouslycorresponding to observed photometrical and kinematical data and chemicalabundances. In this paper we present the observed surface brightness, colourand metallicity distributions, and compare them to the model galaxy. In PaperII (Tempel, Tamm & Tenjes 2007) we present similar data for the kinematics, andderive the mass distribution of the galaxy. On the basis of U, B, V, R, I and Lluminosity distributions, we construct the model galaxy as a superposition offour axially symmetric stellar components: a bulge, a disc, an inner halo andan extended diffuse halo. By using far-infrared imaging data of M31 and a thindust disc assumption, we derive dust-free surface brightness and colourdistributions. We find the total absorption corrected luminosity of M31 to beL_B = (3.3+/-0.7)x10^10 L_sun, corresponding to an absolute luminosity M_B =-20.8+/-0.2 mag. Of the total luminosity, 41% (0.57 mag) is obscured from us bythe dust inside M31. Using chemical evolution models, we calculatemass-to-light ratios of the components, correspoding to the colour indices andmetallicities. We find the total intrinsic mass-to-light ratio of the visiblematter to be M/L_B=3.1-5.8 M_sun/L_sun and the total mass of visible matterM_vis =(10-19)x10^10 M_sun. The use of the model parameters for a dynamicalanalysis and for determining dark matter distribution is presented in Paper II.

Visible and dark matter in M31 - I. Properties of stellar components