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Abstract: Galaxy pairs are ideal sites in which to investigate the role of interactionon nuclear activity. For this reason we have undertaken a spectroscopic surveyof a large homogeneous sample of galaxy pairs UZC-BGP and we present theresults of the nuclear spectral classification of 48 pairs more than half ofthe whole sample. The fraction of emission line galaxies is extremely large,especially among spirals 84 % and 95 %, for early and late spiralsrespectively. SB is the most frequent type of nuclear activity encountered 30% of galaxies while AGNs are only 19%. The fractions raise to 45 % and 22 %when considering only spirals. Late spirals are characterized by both anunusual increase 35 % of AGN activity and high luminosity 44 % have M B<-20.0 + 5log h. LLAGNs are only 8% of the total number of galaxies, but thisactivity could be present in another 10 % of the galaxies LLAGN candidates.Absorption line galaxies reside mostly 61 % in S0 galaxies and display thelowest B luminosity in the sample, only 18 % of them have M B < -20 + 5 log h,but together with LLAGNs they are the most massive galaxies in the sample.Intense-SB nuclei are found in galaxy pairs with galaxy-galaxy projectedseparations up to 160 h^{-1} kpc suggesting that in bright isolated galaxypairs interaction may be at work and effective up to that distance. AGNs arecharacterized by an advanced morphology while SB phenomenon occurs with thesame frequency in early and late spirals. LLAGNs and LLAGN candidates do notalways show similar properties, a finding which might confirm the heterogeneousnature of this class of objects. Half LLAGNs are hosted in galaxies showingvisible signs of interaction with fainter companions, suggesting that minorinteractions might be a driving mechanism for a relevant fraction of LLAGNs.

Autor: Paola Focardi, Valentina Zitelli, Silvia Marinoni


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