GHASP: an Hα kinematic survey of spiral galaxies - X. Surface photometry, decompositions and the Tully-Fisher relation in the Rc band

We present R-c-band surface photometry for 170 of the 203 galaxies in GHASP, the Gassendi H-alpha survey of spirals, a sample of late-type galaxies for which high-resolution Fabry-Perot H alpha maps have previously been obtained. Our data set is constructed using new R-c-band observations taken at the Observatoire de Haute-Provence, supplemented with Sloan Digital Sky Survey archival data, obtained with the purpose of deriving homogeneous photometric profiles and parameters. Our results include R-c-band surface brightness profiles for 170 galaxies and ugriz profiles for 108 of these objects. We catalogue several parameters of general interest for further reference, such as total magnitude, effective radius and isophotal parameters (magnitude, position angle, ellipticity and inclination). We also perform a structural decomposition of the surface brightness profiles using a multi-component method to separate discs from bulges and bars, and to observe the main scaling relations involving luminosities, sizes and maximum velocities. We determine the R-c-band Tully-Fisher relation using maximum velocities derived solely from H alpha rotation curves for a sample of 80 galaxies, resulting in a slope of -8.1 +/- 0.5, zero-point of -3.0 +/- 1.0 and an estimated intrinsic scatter of 0.28 +/- 0.07. We note that, unlike the Tully-Fisher relation in the near-infrared derived for the same sample, no change in the slope of the relation is seen at the low-mass end (for galaxies with V-max < 125 km s(-1)). We suggest that this different behaviour of the Tully-Fisher relation (with the optical relation being described by a single power law while the near-infrared has two), may be caused by differences in the stellar mass-to-light ratio for galaxies with V-max < 125 km s(-1).