Photometry and Kinematics of the Magellanic Type Galaxy NGC 4618

Abstract

NGC 4618 is an excellent example of an asymmetric, late-type Magellanic barred spiral (de Vaucouleurs and Freeman 1972). Detailed surface photometry of this galaxy has been obtained from photoelectrically calibrated V and I CCD images from Asiago Observatory, and from BVR CCD images, UBV electronographic plates, and one filtered IIa-O 2.1-m photographic plate from McDonald Observatory. This material, reduced with the McDonald Observatory Galaxy Photometry Package, is used to derive standard photometric parameters for comparison with previous studies of late type systems, such as that of NGC 4027 (Pence and de Vaucouleurs 1985). The luminosity distribution is decomposed into three distinct components: 1) an elliptical bar, 2) an exponential old disk, and 3) a young H II region/arm population; comprising 23, 50, and 27 percent of the total luminosity, respectively. A detailed mapping of the V — I color index, and Hα imagery are used to study the distribution of young star forming regions with respect to the bar, which is significantly offset from the center of the exponential disk defined by the outer isophotes.