Based on observations obtained at the ESO-NTT in La Silla, at the ESO-VLT in Paranal and at the Italian Telescopio Nazionale Galileo (TNG) operated on the island of La Palma by the Centro Galileo Galilei of the CNAA (Consorzio Nazionale per l'Astronomia e l'Astrofisica) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias.

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${\rm 1SNu = 1SN(100~yr)^{-1}}(10^{10}~L_{\odot}^{\rm B})^{-1}$ .

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... TNG

The Italian Galileo National Telescope.

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... Kuiper/Steward

University of Arizona.

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... $K{\rm s}=16.03\pm 0.20$

The difference with respect to the magnitude given in Maiolino et al. (2001) is due to a better subtraction of the background light.

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... higher

Note that the "pure'' mixed case would give a maximum H $\alpha$ /H $\beta$ ratio of $\sim$ 4.1, implying that at least part of the absorption is ascribed to a simple foreground screen of dust.

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