Imaging and spectroscopy of ten southern galaxies selected from a catalogue of peculiar galaxies

IATE, Observatorio Astronómico, Universidad Nacional de Córdoba, Laprida 854, 5000 Córdoba, Argentina

Send offprint request to: C.J. Donzelli

Received: 10 December 1996
Accepted: 16 June 1997

Abstract

We present BVRI broad band photometry and long slit spectroscopy for a sample of ten southern galaxies selected from the Agüero Catalogue of Peculiar Galaxies.
The analysis of the images shows that only four galaxies of the sample are truly peculiar galaxies and four are normal spirals. The remaining two galaxies, a normal spiral and a SO, form an interacting pair. Despite the rather complicated structure of the peculiar galaxies we did not find evidence of mergers in our analysis of images and rotation curves.
Almost all galaxies in our sample show star forming regions with very blue colors, () ranging from 0.2 to 0.6. The SO galaxy shows a very interesting structure in the color map suggesting that star formation events have occurred in concentric annuli centered in the nucleus. In our photometric analysis we did not find characteristics that could distinguish between normal and peculiar galaxies.
We obtained the "pure-emission” line spectra for six galaxies of the sample by subtracting appropriate templates. These templates correspond to ellipticals selected from our library of spectra. This subtraction technique provides a powerful tool to calculate line flux ratios uncontaminated by the underlying stellar population.
Our spectroscopic analysis confirms that the spiral galaxy of the interacting system AM has a LINER-type nucleus. In the normal galaxy ESO we find evidence of a LINER nucleus and we report a new Seyfert 2 galaxy, AM N. For this SO galaxy the line flux ratios measured from the pure-emission spectrum are indicative of a Seyfert 2 rather than a LINER nucleus as it was previously reported by other authors.
Three of the four peculiar galaxies in our sample have much higher star-formation rate than normal galaxies, as measured by Hα + [NII] line emission. The observed EW(Hα + [NII]) values for these peculiar galaxies are around 60 Å, compared to 22 Å for normal galaxies. Whole-aperture spectra for these peculiar galaxies show very similar EW(Hα + [NII]) values to those observed in their nuclear region suggesting that a global starburst has occurred. Although our sample is small the results presented suggest that peculiar morphology and global starburst events are closely related.