Scale Length of Disk Galaxies

Abstract

Disk scale length r_d and central surface brightness μ₀ for a sample of 29955 bright disk galaxies from the Sloan Digital Sky Survey have been analyzed. Cross correlation of the SDSS sample with the LEDA catalogue allowed us to investigate the variation of the scale lengths for different types of disk/spiral galaxies and present distributions and typical trends of scale lengths all the SDSS bands with linear relations that indicate the relation that connect scale lengths in one passband to another. We use the volume corrected results in the r-band and revisit the relation between these parameters and the galaxy morphology, and find the average values 〈r_d〉 = 3.8 ± 2.1 kpc and 〈μ₀〉 = 20.2 ± 0.7 mag arcsec⁻². The derived scale lengths presented here are representative for a typical galaxy mass of 10^10.8 M_⊙, and the RMS dispersion is larger for more massive galaxies. We analyse the r_d–μ₀ plane and further investigate the Freeman Law and confirm that it indeed defines an upper limit for μ₀ in bright disks (r_mag < 17.0), and that disks in late type spirals (T ≥ 6) have fainter central surface brightness. Our results are based on a sample of galaxies in the local universe (z < 0.3) that is two orders of magnitudes larger than any sample previously studied, and deliver statistically significant results that provide a comprehensive test bed for future theoretical studies and numerical simulations of galaxy formation and evolution.