The nature of arms in spiral galaxies ^*

II. The sample

¹ INAOE, 72000 Puebla, Mexico
² Instituto de Astrofísica de Canarias, 38200 La Laguna, Tenerife, Spain
³ Departamento de Astrofísica, Facultad de Física, Universidad de La Laguna, 38071 La Laguna, Tenerife, Spain

Corresponding author: M. S. del Río, sole@inaoep.mx

Received: 13 February 1998
Accepted: 7 October 2002

Abstract

We present here the results of an imaging study of eight grand-design and two intermediate-arm galaxies, based on CCD observations in U, B, V, R and I. We give grey-scale images, both in individual and in colour indices. Also we present a decomposition into bulge and disc following an iterative method. This provides us with a reasonable estimate of the bulge size and disc scale length, and shows the disc deviation from an exponential law, which can be interpreted as due to the long-term star formation caused by the spiral arms. To evaluate the contribution of the spiral arms to the disc luminosity distribution, with the aid of a mask we have decomposed each image into two parts: arms (which include bulge and nucleus, and eventually bars) and inter-arms (which include the outer disc).
In subsequent papers in this series (del Río & Cepa [CITE], hereafter Paper III; del Río & Cepa [CITE], hereafter Paper IV) the data presented here are used to analyse the spiral structure of the galaxies of the sample, using the methods of Beckman & Cepa ([CITE], hereafter Paper I) and the Fourier transform method to find the different symmetry degrees.