Left to right: optical depth τ, dust temperature T (in kelvin), and spectral index β_d of the dust component in the Virgo region. Some clusters in this field of view (Coma to the north, Leo to the east, and Virgo near the centre) can be clearly spotted as artefacts in the T and β_d maps. The coordinates are Galactic and the field of view resembles that of Fig. 1 () and other figures in this paper.