SIMBAD references

We present a re-evaluation of the optical morphology for 549 galaxies from the Catalog of Isolated Galaxies in the Northern Hemisphere (CIG) that are available in the Sloan Digital Sky Survey (SDSS; DR6). Both the high resolution and high dynamic range of the SDSS images and our semiautomatic image processing scheme allow for a major quality and uniform morphological analysis. The processing scheme includes (1) sky-subtracted, cleaned, and logarithmic scaled g-band images, (2) filtered-enhanced versions of the images in (1), and (3) the corresponding red-green-blue (RGB) composed images available in the SDSS database. We propose an empirical method to distinguishing between E, S0, and Sa candidates through an additional analysis of (4) the surface brightness, position angle, ellipticity and A₄B₄ coefficients of the Fourier series expansion profiles. An atlas of mosaics containing (1), (2), and (3) images for Sab-Sm/Irr types and (1), (2), (3), (4) images for E/S0/Sa types was produced and is available on the Web. The median type in the sample corresponds to Sbc, with 65% of the sample being of this type or later. A scarce population of early-type E (3.5%) and S0 (5%) galaxies amounting to 8.5% and a non-negligible 14% fraction of early-type (SaSab) spirals are identified. We compare our results with a previous reclassification of the CIG based on the digitized Palomar Observatory Sky Survey II images. We calculate also the gri absolute magnitudes corrected by Galactic and internal extinctions and present the g - i color distribution and the color-magnitude diagram. Among the spirals, we find tentative fractions of strong and suspected bars of 65.8% and of 33.3% of rings. A detailed image analysis of the E galaxies (18) allows us to find a richness of distinct substructure in their isophotal shape and also of morphological distortions. At least 78% of the E galaxies show some kind of morphological distortion (shells, dust lanes, diffuse halos, etc.), suggesting that these galaxies suffered late dry mergers. The isophotes of 42% (37%) of the E galaxies are boxy (disky). Among four blue Es, three are disky. Finally, we calculate the CAS (concentration, asymmetry and clumpiness) structural parameters in the ugriz bands for the entire sample. We analyze the loci of these galaxies in different projections of the CAS volume diagram and discuss some trends of the CAS parameters with the color band, as well as with the morphological type and the galaxy color.