We present a complete refinement of the optical morphologies for galaxies in the Catalog of Isolated Galaxies ( Karachentseva [ 1973 ] ) that forms the basis of the AMIGA ( Analysis of the interstellar Medium of Isolated GAlaxies ) project .
Uniform reclassification using the digitized POSS II benefited from the high resolution and dynamic range of that sky survey .
Comparison with independent classifications made for an SDSS overlap sample of more than 200 galaxies confirms the reliability of the early vs. late-type discrimination and the accuracy of spiral subtypes within \Delta T = 1–2 .
CCD images taken at the Observatorio de Sierra Nevada were also used to solve ambiguities in early versus late-type classifications .
A considerable number of galaxies in the catalog ( n = 193 ) are flagged for the presence of nearby companions or signs of distortion likely due to interaction .
This most isolated sample of galaxies in the local Universe is dominated by two populations : 1 ) 82 % spirals ( Sa–Sd ) with the bulk being luminous systems with small bulges ( 63 % between types Sb–Sc ) and 2 ) a significant population of early-type E–S0 galaxies ( 14 % ) .
Most of the types later than Sd are low luminosity galaxies concentrated in the local supercluster where isolation is difficult to evaluate .
The late-type spiral majority of the sample spans a luminosity range M _ { B { - corr } } = - 18 to - 22 mag .
Few of the E/S0 population are more luminous than - 21.0 marking an absence of , an often sought , super L ^ { * } merger ( e.g .
fossil elliptical ) population .
The rarity of high luminosity systems results in a fainter derived M ^ { * } for this population compared to the spiral optical luminosity function ( OLF ) .
The E–S0 population is from 0.2 to 0.6 mag fainter depending how the sample is defined .
This marks the AMIGA sample as almost unique among samples that compare early and late-type OLFs separately .
In other samples , which always involve galaxies in higher density environments , M ^ { * } _ { E / S 0 } is almost always 0.3–0.5 mag brighter than M ^ { * } _ { S } , presumably reflecting a stronger correlation between M ^ { * } and environmental density for early-type galaxies .