Redshift evolution of z′− NB980 colours of various galaxies. The colours of E (elliptical), Sbc, Scd and Im (irregular) galaxies were calculated using Coleman et al. (1980) template spectra. The colours of LBGs/LAEs were calculated using the spectrum fλ∝λβ for several UV continuum slopes β and Lyα EWs 
. Left: the colours of LBGs (
), which show the excess of 
at z∼ 7–7.1 (horizontal line), but the maximum excess at z∼ 7–7.05 does not depend on β. Right: the colours of an LBG and LAEs with β=−3 are plotted as a representative, because Ono et al. (2010) suggest that z∼ 7 LBGs and z= 5.7 and 6.6 LAEs tend to have β≃−3. The LAEs clearly show the excess of z′− NB980 > 2.5 at z∼ 7–7.1, which we have adopted as the LAE selection criterion 3 (see Section 3.2). This criterion can detect both z∼ 7–7.1 LBGs (
Å) and LAEs (
Å).
