Colours vs. absolute z_PS1 magnitude diagrams of metal-poor T dwarf candidates (blue crosses), using trigonometric parallaxes obtained from this work and from the literature, z_PS1 photometry from this work and from Zhang et al. (2023) and IR photometry from the literature. The parallax of W1810 comes from Lodieu et al. (2022). For the Accident (black cross and arrow), the parallax comes from (Kirkpatrick et al. 2021a). For comparison, field M, L, T dwarfs with trigonometric parallaxes from Pan-STARRS1 3π survey (Best et al. 2018) are plotted as yellow stars, orange squares, and red dots, respectively. Y dwarfs with z_PS1 photometry (corrected from z′) from Lodieu et al. (2013) and Martín et al. (2024), and parallaxes from Kirkpatrick et al. (2019) are plotted as purple triangles. W1217 is a T9+Y2 system, so it is plotted as a mixture of red dot and purple triangle.