Magnitude and size evolution of bulgeless galaxies
  We examine the magnitude and size evolution of bulgeless (discs with no-bulge
or pseudo-bulge) galaxies up to z~0.9 in rest-frame B-band. Their evolution is
compared to that of normal-discs (discs with classical-bulge). The study is
done for luminous sources (M_B<=-20) in two equal-volume redshift-bins
(0.4<=z<0.77 and 0.77<=z<1.0) and a local range (0.02<=z<0.05). The mean
surface-brightness, from z_{mean}=0.89 to z_{mean}=0.04, shows a dimming of
0.79 mag for bulgeless galaxies and 1.16 mag for normal-discs. The
characteristic magnitude, M_B^*, shows an increase of 0.55-mag for bulgeless
galaxies and 0.95-mag for normal-discs. Both dimming and faintness observed
since z~0.9 are more pronounced for the normal-discs by ~0.4-mag. The
size-distribution is log-normal and both bulgeless and normal-discs show a
slight increase in the mean value from z_{mean}=0.89 to z_{mean}=0.04. The
proportion of bulgeless galaxies in the full disc sample undergoes a
considerable decline with decrease in redshift. This along with the larger
dimming and faintness seen for normal-discs suggests that some fraction of the
bulgeless sources switch to the normal-disc morphology with time. To ascertain
the validity of studying morphology in the optical, the properties of the
galaxies observed in both rest-frame B and I-band are compared. The common
sample is more luminous in the I-band but the sizes are larger in the B-band
for more than 74 % of the sources. The variation in the sersic-index values of
the galaxies in the two rest-bands is minor enough to have any affect on the
morphological classification.
