Abstract

Isophotes, luminosity profiles, and photometric parameters of the brightest southern Seyfert galaxy NOC 1566, revised type SAB(s)bc, are derived from long- and short-exposure photographs taken with the Mount Stromlo 75-cm reflector and the Cordoba 152-cm reflector. The total apparent magnitude m (B) = 10.32 (photoelectrically calibrated) and maximum dimensions 9.5 x 8'S (at the detection threshold 26.5 mag = 1.65 L0 pc-2) correspond to MT(B) = -20.3 and Dm = 32 kpc if m - M = 30.6 andA = 11.5 Mpc, estimated from membership in the Dorado group of which NOC 1566 is the dominant member. A weak bar structure is in p.a. 354 (1875), the major axis of the main body including the two brighter spiral arms is in p.a. 20 , while faint outer arms form a pseudo ring (R') = 7.5 x 7.0 whose major axis is in p a _ 50 the inclination derived from the ellipticity of the outer ring is i 30 . The equivalent effective radius is = 110 = 3.35 kpc, and the gradient of the exponential (flat) component is G(a) = -0.44 arc = -0.13 kpc-1 for a lie length scale A = 3.3 kpc, all closely comparable to the corresponding parameters in normal (non-Seyfert) spirals such as M 31, M33, and NGC 6744. The magnitude mn(B) of the quasi-stellar nucleus derived from analyses of the aperture-magni - tude relation is variable between 13.5 (MN = - 17.1) and 14.6 (MN = - 16.0); it contributes from 2 to 5 percent of the total B luminosity of the system; this is rather less than the average for other Seyfert galaxies. Subject headings: galaxies, photometry of - Seyfert galaxies