Autocorrelations of stellar light and mass in the low-redshift Universe
  The final data release of the Sloan Digital Sky Survey (SDSS) provides
reliable photometry and spectroscopy for about half a million galaxies with
median redshift 0.09. Here we use these data to estimate projected
autocorrelation functions w_p(r_p) for the light of galaxies in the five SDSS
photometric bands. Comparison with the analogous stellar mass autocorrelation,
estimated in a previous paper, shows that stellar luminosity is less strongly
clustered than stellar mass in all bands and on all scales. Over the full
nonlinear range 10 kpc/h < r_p < 10 Mpc/h our autocorrelation estimates are
extremely well represented by power laws. The parameters of the corresponding
spatial functions \xi(r) = (r/r_0)^\gamma vary systematically from r_0=4.5
Mpc/h and \gamma=-1.74 for the bluest band (the u band) to r_0=5.8 Mpc/h and
\gamma=-1.83 for the reddest one (the z band). These may be compared with
r_0=6.1 Mpc/h and \gamma=-1.84 for the stellar mass. Ratios of w_p(r_p) between
two given wavebands are proportional to the mean colour of correlated stars at
projected distance r_p from a randomly chosen star. The ratio of the stellar
mass and luminosity autocorrelations measures an analogous mean stellar
mass-to-light ratio (M*/L). All colours get redder and all mass-to-light ratios
get larger with decreasing r_p, with the amplitude of the effects decreasing
strongly to redder passbands. Even for the u-band the effects are quite modest,
with maximum shifts of about 0.1 in u-g and about 25% in M*/L_u. These trends
provide a precise characterisation of the well-known dependence of stellar
populations on environment.
