A lopsided chemically distinct nucleus in NGC 5055

Abstract

Kinematics and stellar population properties in the center of nearby Sbc galaxy NGC 5055 are studied with the Multi-Pupil Spectrograph of the 6 m telescope of the Special Astrophysical Observatory of Russian Academy of Sciences (SAO RAS). We confirm the rotation and stellar velocity dispersion asymmetries along the major axis reported earlier by other authors. We have found a resolved chemically distinct core in NGC 5055, with the magnesium-enhanced region shifted by 2farcs 5 (100 pc) to the south-west from a photometric center, toward a kinematically identified circumnuclear stellar disk. Mean ages of stellar populations in the true nucleus, defined as the photometric center, and in the magnesium-enhanced substructure are coincident and equal to 3-4 Gyr being younger by several Gyr with respect to the bulge stellar population. A possible origin of the asymmetries in the center of NGC 5055 is discussed. Based on observations collected with the 6 m telescope of the Special Astrophysical Observatory (SAO) of the Russian Academy of Sciences (RAS) which is operated under the financial support of Science Department of Russia (registration number 01-43) and on data from the HST Archive.