Broad-band BVRI photometry of isolated spiral galaxies*
Instituto de Astronomía, Universidad Nacional Autónoma de México, Apartado Postal 70-264, 04510 México D. F., México e-mail: [hector;sortega]@astroscu.unam.mx
Accepted: 14 May 2008
Context. Uniform and high resolution observations in samples of isolated galaxies are required to estimate fundamental morphological and structural parameters for comparative studies of environmental effects and for confronting model predictions of galaxy evolution. A subsample of The Catalog of Isolated Galaxies (CIG), Karachentseva (1973), has been uniformly observed at San Pedro Mártir National Observatory in México and a photometric and morphological study of these galaxies has been carried out.
Aims. We report multicolor broad band (BVRI) photometry for a subsample of 40 isolated spirals drawn from the CIG. Total magnitudes and colors at various circular apertures as well as a detailed morphological analysis that is extended into the NIR bands are presented. Some structural parameters are estimated from the global light distribution in the optical and NIR bands to complement our morphological analysis and several correlations between the photometric and structural parameters are explored. Emphasis was given to the detection of morphological distortions at high/low intensity levels.
Methods. The observations, data reduction, and analysis are described. Morphology is reevaluated from a combination of optical logarithmically scaled R band images, filter-enhanced R band images, () color index maps, archived near IR images from the TwoMicron Survey and optical-NIR ϵ and PA radial profiles after an isophotal analysis. images from the SDSS database were retrieved when available to complement our analysis. The structural parameters (Concentration, Asymmetry, and Clumpiness) were calculated from the images in each band.
Results. The fraction of galaxies with well-identified optical/near-IR bars (SB) is 40%, while another 25% shows evidence of weak or suspected bars (SAB). The sample average value of the maximum bar ellipticity is . 57.5% of the galaxies in the sample show rings. The parameters change with the observed band, the morphological type and global color. We found 9 isolated galaxies with disturbed morphology. After reviewing their local number density and tidal strength parameters, we identified CIG 744 as a morphologically disturbed isolated galaxy having ; a tentative candidate to interact with a dark gas-rich object. However, its loci in the diagram, suggests that CIG 744 is itself a gas-rich disturbed-isolated galaxy probably in a lengthy or ongoing process of formation, instead.
Key words: galaxies: spiral / galaxies: structure / galaxies: photometry / galaxies: interactions / galaxies: fundamental parameters / galaxies: general
© ESO, 2008