A large sample of low surface brightness disc galaxies from the SDSS – I. The sample and the stellar populations

We present the properties of a large sample (12 282) of nearly face-on low surface brightness (LSB) disc galaxies selected from the main galaxy sample of SDSS-DR4. These properties include B-band central surface brightness μ 0 (B), scalelengths h, integrated magnitudes, colours and distances D. This sample has μ 0 (B) values from 22 to 24.5 mag arcsec -2 with a median value of 22.42 mag arcsec -2 , and disc scalelengths ranging from 2 to 19 kpc. They are quite bright with M B taking values from -18 to -23 mag with a median value of -20.08 mag. There exist clear correlations between log h and M B , log h and log D, log D and M B . However, no obvious correlations are found between μ 0 (B) and log h, colours, etc. The correlation between colours and log h is weak even though it exists. Both the optical-optical and optical-NIR colour-colour diagrams indicate that most of them have a mixture of young and old stellar populations. They also satisfy colour-magnitude relations, which indicate that brighter galaxies tend generally to be redder. The comparison between the LSBGs and a control sample of nearly face-on disc galaxies with higher surface brightness (HSB) with μ 0 (B) from 18.5 to 22 mag arcsec -2 show that, at a given luminosity or distance, the observed LSB galaxies tend to have larger scalelengths. These trends could be seen gradually by dividing both the LSBGs and HSBGs into two subgroups according to surface brightness. A volume-limited subsample was extracted to check the incompleteness of surface brightness. The only one of the property relations having an obvious change is the relation of log h versus μ 0 (B), which shows a correlation in this subsample.