21-cm self-absorption: a21
The self absorption is given in magnitude scale and is related to the galaxy
inclination xi through the formulae
a21=2.5log(cf), where:
- if 0. < xi < 50. , cf=1.02
- if 50 < xi < 89. , cf=(0.031/cos(xi))/(1.-exp(-0.031/cos(xi)))
- if xi > 89. , cf= 2.14
The corrected 21-cm line magnitude m21 is expressed as:
m21c = m21 - a21
See
Heidmann et al 1972 for details.