Internal extinction: ai

The dust extinction within galaxies in the B-band, ai [mag] is computed after Bottinelli et al. 1995, A&A296, 64.

This formula is a function of the morphological type, t, and of the apparent flattening, logr25.

where m0 is the corrected magnitude and mi is the observed one;

R is the axis ratio derived from logr25

k is the bulge to disk ratio and depends on morphological type as follows: k=0.754*10(-0.2*t), if  k >1 then k=1 (Simien and de Vaucouleurs)

K is the coefficient dlogD/db (where D is the isophotal diameter at surface brightness b). It depends on the morphological type t as:
K = 0.12-0.007*t  if  t < 0.
K = 0.094  if  t >= 0.

and C is defined as (dlogD/dlogR) and has the fixed value of 0.04