Free access article

A&A 429, 825-836 (2005)
DOI: 10.1051/0004-6361:20040311

The Leo Triplet: Common origin or late encounter?

V. L. Afanasiev¹ and O. K. Sil'chenko<sup>2, 3, 4

1</sup>  Special Astrophysical Observatory, Nizhnij Arkhyz, 369167 Russia
²  Sternberg Astronomical Institute, University av. 13, Moscow 119992, Russia
    e-mail: olga@sai.msu.su
³  Isaac Newton Institute of Chile, Moscow Branch, Russia
⁴  UK Astronomy Data Centre, Guest Investigator, UK

(Received 20 February 2004 / Accepted 27 August 2004)

Abstract
The kinematics, structure, and stellar population properties in the centers of two early-type spiral galaxies of the Leo Triplet, NGC 3627 and NGC 3623, are studied by means of integral-field spectroscopy. Unlike our previous targets, NGC 3384/NGC 3368 in the Leo I Group and NGC 5574/NGC 5576 in LGG 379, NGC 3623 and NGC 3627 do not appear to experience a synchronous evolution. The mean ages of their circumnuclear stellar populations are quite different, and the magnesium overabundance of the nucleus in NGC 3627 is evidence for a very brief last star formation event 1 Gyr ago whereas the evolution of the central part of NGC 3623 looks more quiescent. In the center of NGC 3627 we observe noticeable gas radial motions, and the stars and the ionized gas in the center of NGC 3623 demonstrate more or less stable rotation. However, NGC 3623 has a chemically distinct core - a relic of a past star formation burst - which is shaped as a compact, dynamically cold stellar disk with a radius of ~ 250-350 pc which has been formed not later than 5 Gyr ago.

Key words: galaxies: individual: NGC 3623 -- galaxies: individual: NGC 3627 -- galaxies: nuclei -- galaxies: stellar content -- galaxies: kinematics and dynamics -- galaxies: evolution

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