EDP Sciences
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Volume 409, Number 1, October I 2003
Page(s) 91 - 97
Section Galactic structure and dynamics
DOI http://dx.doi.org/10.1051/0004-6361:20031083

A&A 409, 91-97 (2003)
DOI: 10.1051/0004-6361:20031083

On the nature of the galaxy NGC 5666

C. J. Donzelli1 and E. Davoust2

1  IATE, Observatorio Astronómico, Universidad Nacional de Córdoba, & CONICET, Laprida 854, 5000, Córdoba, Argentina
2  UMR 5572, Observatoire Midi-Pyrénées, 14 avenue E. Belin, 31400 Toulouse, France

(Received 8 April 2003 / Accepted 2 July 2003)

We present B and R CCD images and optical spectroscopy in the range 3700-8900 Å for the galaxy NGC 5666, which until now was considered as a low-luminosity elliptical. The high-resolution images show a conspicuous spiral pattern which is limited to the inner region ( $r \le 5\arcsec$, or 1/6 of the isophotal radius) and a faint (presumably tidal) outer feature dotted with small knots resembling star clusters or tidal dwarf galaxies. The patchy spiral structure and the luminosity profiles suggest a late-type morphological type, but the disk is of high central surface brightness and the bulge weak and very extended. The nuclear spectrum reveals typical emission lines found in late-type galaxies, but the underlying nuclear stellar population and continuum only match that of an elliptical galaxy combined with a young ( <1 Gyr) stellar population. These and other properties of the galaxy suggest that this could be a minor merger, at an intermediate stage, between a gas-rich dwarf and a small early-type disk galaxy. If this is the case, the galaxy NGC 5666 will provide important constraints to the theory of hierarchical galaxy formation.

Key words: galaxies: photometry

Offprint request: C. J. Donzelli, charly@oac.uncor.edu

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