Young Nuclei in Elliptical Galaxies

O. K. Sil’chenko

Sternberg Astronomical Institute, Universitetskii pr. 13, Moscow, 119899 Russia

Received November 11, 1996

Abstract—Chemically distinct nuclei have been found in the three elliptical galaxies NGC 4564, NGC 4621, and NGC 5576. These nuclei are appreciably younger than the surrounding regions: in the nuclei of NGC 4564 and NGC 4621, the mean age of the stellar population is 8 billion years, and in NGC 5576, it is 3 billion years. Studies of the rotation of the stellar component in the central regions of these galaxies revealed circular rotation in the main plane in NGC 4564 and NGC 4621; the asymmetric absorption line profiles and photometric structure of the nucleus in NGC 4621 indicates that there is a nuclear disk with dimensions 5–7. In NGC 5576, the nucleus is the most compact and rotates in a plane perpendicular to the main plane of the galaxy. It is proposed that the difference in the structure of chemically distinct young nuclei in elliptical galaxies is due to the different angular momentum of the accreted gas that formed these nuclei.

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