ALBERT

Description: We present Very Large Telescope/Visible Multiobject Spectrograph Integral Field Unit observations of an occulting galaxy pair previously discovered in Hubble Space Telescope ( HST ) observations. The foreground galaxy is a low-inclination spiral disc, which causes clear attenuation features seen against the bright bulge and disc of the background galaxy. We find redshifts of z  = 0.064 ± 0.003 and 0.065 for the foreground and background galaxy, respectively. This relatively small difference does not rule out gravitational interaction between the two galaxies. Emission line ratios point to a star-forming, not active galactic nuclei dominated foreground galaxy. We fit the Cardelli, Clayton and Mathis extinction law to the spectra of individual fibres to derive slope ( R V ) and normalization ( A V ). The normalization agrees with the HST attenuation map and the slope is lower than the Milky Way relation ( R V  〈 3.1), which is likely linked to the spatial sampling of the disc. We speculate that the values of R V point to either coherent interstellar medium structures in the disc larger than usual (~9 kpc) or higher starting values of R V , indicative of recent processing of the dust. The foreground galaxy is a low stellar mass spiral ( M *  ~ 3  x 10 9 M ) with a high dust content ( M dust  ~ 0.5  x 10 6 M ). The dust disc geometry visible in the HST image would explain the observed spectral energy distribution properties of smaller galaxies: a lower mean dust temperature, a high dust-to-stellar mass ratio but relatively little optical attenuation. Ongoing efforts to find occulting pairs with a small foreground galaxy will show how common this geometry is.