Chemically decoupled nucleus and the structure of the nuclear region in the spiral galaxy NGC 488

Abstract

The regular Sb-type galaxy NGC 488 was observed at the 6-meter telescope with the Multi-Pupil Field Spectrograph and found to have a chemically decoupled nucleus. Stellar population in the nucleus is twice richer in metals than that of the central bulge. An analysis of the isophotal shapes in the central part of the galaxy based on the images obtained with broad-band filters allowed us to identify two isolated stellar components in NGC 488: one in the radial range between 1 and 2 arcsec and another in the R 4-7 arcsec interval. The coincidence of photometric and dynamical major axes proves that both components are compact circumnuclear disks tilted with respect to the plane of the global galactic disk. The stellar disk at the very center of the galaxy, which ends at R = 2 arcsec, has a gaseous extension up to R = 4 arcsec. In both stellar disks, a low-contrast spiral pattern can be distinguished.