Scalelength of disc galaxies

We have derived disc scalelengths for 30 374 non-interacting disc galaxies in all five Sloan Digital Sky Survey (SDSS) bands. Virtual Observatory methods and tools were used to define, retrieve and analyse the images for this unprecedentedly large sample classified as disc/spiral galaxies in the LEDA catalogue. Cross-correlation of the SDSS sample with the LEDA catalogue allowed us to investigate the variation of the scalelengths for different types of disc/spiral galaxies. We further investigate asymmetry, concentration and central velocity dispersion as indicators of morphological type, and are able to assess how the scalelength varies with respect to galaxy type. We note, however, that the concentration and asymmetry parameters have to be used with caution when investigating type dependence of structural parameters in galaxies. Here, we present the scalelength derivation method and numerous tests that we have carried out to investigate the reliability of our results. The average r-band disc scalelength is 3.79 kpc, with an rms dispersion of 2.05 kpc, and this is a typical value irrespective of passband and galaxy morphology, concentration and asymmetry. The derived scalelengths presented here are representative for a typical galaxy mass of 1010.8 +/- 0.54 M-circle dot, and the rms dispersion is larger for more massive galaxies. Separating the derived scalelengths for different galaxy masses, the r-band scalelength is 1.52 +/- 0.65 kpc for galaxies with total stellar mass 109-1010 M-circle dot and 5.73 +/- 1.94 kpc for galaxies with total stellar mass between 1011 and 1012 M-circle dot. Distributions and typical trends of scalelengths have also been derived in all the other SDSS bands with linear relations that indicate the relation that connect scalelengths in one passband to another. Such transformations could be used to test the results of forthcoming cosmological simulations of galaxy formation and evolution of the Hubble sequence.