Hi Benji,Benjamin Mauclaire wrote:Hello,
Bertrand tu sembles confondre décalage Doppler et vitesse d'expension, respectivement ici de 248 A (-11699 kms) et 0.5fwhm=~100 A (4830 kms)
Benji
No Etienne is correct. The absorption line shows velocity in our direction. There is a spread of velocities at different depths but the mean velocity is that which Etienne has calculated. This is different from emission lines, for example in type II supernovae, where the width of the line shows the velocity between the maximum in our direction and zero to the side (and if optically thin, the velocity away from us)
Cheers
Robin