Surface VRI photometry and the structure of the ”dusty” galaxy NGC 972статья
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Аннотация:We present the VRI CCD photometry of the spiral galaxy NGC 972 that was obtained with the 1-m Zeiss reflector at the Special Astrophysical Observatory (Russian Academy of Sciences). This galaxy exhibits no ‘classical’ spiral pattern. However, it contains a fairly large amount of gas, and its inner region shows numerous dark lanes which are evidently associated with the perturbed dust layer. The radial brightness profile of NGC 972 can be represented as the sum of two exponential disks with differing scale lengths and a small compact bulge. The color distribution in the inner part of the galaxy is highly nonuniform and asymmetric. We propose to use the combined color index Q_VRI, which is unaffected by selective absorption, to analyze the color differences. The Q_VRI distribution reveals a ‘blue’ (with a low value of Q_VRI ) nucleus and a ‘redder’ inhomogeneous inner disk with r ~ kpc. We conclude that the star-forming regions in the galactic nucleus and in the inner disk have a major effect on Q_VRI. We use the previously published long-slit spectroscopic observations to model the mass distribution in NGC 972. The galaxy contains a relatively massive dark halo which dominates the disk by mass at r \gt 5 kpc.