Estimates of pD as a function of R from the Planck radiance map measured along the line of sight of SDSS red galaxies at 0.15 < z < 0.25 (left), 0.25 < z < 0.30 (middle) and 0.30 < z < 0.35 (right). The grey colour map accounts for the density of sources. The red dots (and error bars) represent the median (and standard deviation) estimated through bootstrapping resampling of pD and R within the range 2 < R < 20 × 10^-8 W m^-2 sr^-1 split in 20 bins of equal number of sources. The red line is a linear fit to the dots. We find p_LRG ~ 5.85, 5.65 and 5.56 × 10⁵ m² sr W^-1 for 0.15 < z < 0.25, 0.25 < z < 0.30 and 0.30 < z < 0.35 respectively. The blue dashed line shows the p_P14 = 5.4 × 10⁵ derived by P14 from a quasar sample at 0.7 < z < 1.7 (P14).