Voronoi Halo is an artwork by Alistair McClymont in collaboration with the cosmologist Dr. Rita Tojeiro. This website is a tool that McClymont created using data shared by Dr. Tojeiro, the artwork itself can be found here.
This diagram shows a Voronoi pattern using a set of galaxies and quasars from the Sloan Large Sky Survey. The sliders control the "z" position of a slice through a section of the universe. Imagine travelling out through space and looking at the galaxies and quasars around you in that area.
Imagine a cylinder that extends into space, the first slider is the length of that cylinder, the second slider is how far you're pushing that cylinder out into space.
The pattern of lines is a Voronoi diagram, a set of cells each of which defines an area that is closest to one of the galaxies or quasars, each galaxy is represented by a circle.
Voronoi patterns help to show collections of dark matter, the smaller the cells the more dark matter. It is the dark matter that attracts normal matter and forms the structure of the universe. As the cells get smaller they've been coloured to help show the concentration of dark matter.
The data is from this website
the plate is 10475
You can enter the query below into the SDSS query tool to get the data
select top 1000 spa.ra, spa.dec, spa.dered_r as magnitude,
spa.class, spa.z, soa.xfocal as x, soa.yfocal as y
from specphotoAll as spa
join specObjAll as soa on soa.specObjID = spa.specObjID
where spa.plate = 10475
and spa.dered_r > 0
order by spa.dered_r asc