Photometry and structure of lenticular galaxies. I - NGC 3115

Photometric parameters characteristic of the nebula, such as total integrated magnitudes and colors as well as intrinsic photometric quantities, were obtained. Each luminosity profile was decomposed into the contributing luminosity components and fitted by appropriate luminosity laws. De Vaucouleurs's empirical r to the yx law described the nuclear bulge well, whereas an exponential luminosity distribution probably due to the envelope became obvious along all profiles in the outer regions. On the axis along the fundamental plane of the galaxy (major axis), additional luminosity components due to the lens and a possible internal 'ring' became quite obvious. They could best be fitted by Gaussian distributions. Analysis of several cross sections perpendicular to the major axis at various distances from the center indicated that the thin disk so prominent in lenticular nebulae is not seeing-limited and has Gaussian distribution in the direction perpendicular to the galaxy's equatorial plane, merging into an extensive exponential decay, very probably due to the surrounding envelope. An extensive exponential envelope appears to be present in NGC 3115.