Environmental effects on nearby debris discs

Because older stars show a larger dispersion of space velocity values, we have investigated the impact of the debris disc ages on our results. The observed debris disc occurrence rates show a dependence on the stellar space velocities as expected under the hypothesis that stars with larger space velocities have a higher probability of losing their circumstellar dust. The percentage of sources with debris discs in our sample reaches a maximum of ~=25% for stars with low values of the space velocity component |Urel|, relative to the Local ISM, and decreases monotonically for larger |Urel| values down to the 10% level.

A decrease of the average disc fractional luminosity as a function of |Urel| is also observed. These dependencies do not disappear after accounting for the reported higher dispersion of U values with age. In extended discs, the impact of the ISM could also explain the trends observed for the debris disc's projected ellipticities, position angles, and radii with the stellar space velocities.

The fractional luminosities of the debris discs appear to be correlated with their position angles, suggesting that the effect of the ISM on the dust content could depend on the disc orientation. Although these indications may not be fully conclusive on their own, they collectively reinforce the hypothesis that the ISM influences the occurrence rates and morphologies of debris discs, thereby motivating additional research on the impact of the environment.