Distributions of RR Lyrae stars in distance (a)from the Sun and (b) from the Galactic plane.The shaded part of the histogram corresponds to stars with known proper motions.The curve in the left histogram is a power-law approximation for the growth of the number of stars with distance in the intial sample for R < 1.75 kpc. 
is the power-law exponent. The dip in the right distribution near Z
± 250 pc is due to selection effects.discussion in the text | next figure