The impact of void environment on AGN
  We study the population of active galaxies in void environment in the SDSS.
We use optical spectroscopic information to analyze characteristics of the
emission lines of galaxies, accomplished by WHAN and BPT diagrams. Also, we
study WISE mid-IR colours to assess AGN activity. We investigate these
different AGN classification schemes, both optical and mid-IR, and their
dependence on the spatial location with respect to the void centres. To this
end, we define three regions: void, the spherical region defined by voidcentric
distance relative to void radius (distance/r$_{\rm void}$) smaller than 0.8,
comprising overdensities lesser than -0.9, an intermediate/transition shell
region (namely void--wall) 0.8 $<$ distance/r$_{\rm void} <$ 1.2, and a region
sufficiently distant from voids, the field: distance/r$_{\rm void} >$ 2. We
find statistical evidence for a larger fraction of AGN and star--forming
galaxies in the void region, regardless of the classification scheme addressed
(either BPT, WHAN or WISE). Moreover, we obtain a significantly stronger
nuclear activity in voids compared to the field. We find an unusually large
fraction of the most massive black holes undergoing strong accretion when their
host galaxies reside in voids. Our results suggest a strong influence of the
void environment on AGN mechanisms associated with galaxy evolution.
