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Astron. Astrophys. 347, 55-62 (1999)

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Nuclear activity and stellar population of a sample of interacting galaxies *

M.G. Pastoriza 1,3, C.J. Donzelli 2,3 and C. Bonatto 1

1 Departamento de Astronomia, IF-UFRGS, C.P. 15051, CEP 91501-970, Porto Alegre, RS, Brazil
2 IATE, Observatorio Astronômico, Universidad Nacional de Córdoba, Laprida 854, 5000, Córdoba, Argentina
3 Visiting Astronomer at CASLEO Observatory

Received 11 September 1998 / Accepted 19 March 1999

Abstract

In this paper we investigate the nuclear activity and stellar population in a sample of 27 physical galaxy pairs. Equivalent widths of absorption features are used to characterise the nuclear stellar population according to templates: most galaxies of the sample have important flux contributions from stars younger than [FORMULA] years. According to classical diagnostic-diagrams the galaxies in our sample are either classified as H II regions or have emission line ratios near the transition zone between H II regions and LINERs. Based on the observed spectra, only 4 galaxies show LINER properties and 1 nucleus is a Seyfert 2. We found that the spectrum of a transition object (38% of the sample) can be described by a combination of an AGN with an H II region. As a result, 20 galaxies of the present sample may host a low-luminosity active nucleus.

Key words: galaxies: active – galaxies: interactions – galaxies: nuclei – galaxies: stellar content

* Based on observations made at CASLEO and CTIO. Complejo Astronómico El Leoncito (CASLEO) is operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the National Universities of La Plata, Córdoba and San Juan.

Send offprint requests to: M.G. Pastoriza

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© European Southern Observatory (ESO) 1999

Online publication: June 18, 1999
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