redshift in astrophysical plots Why do astrophysicists often use redshift in plots? Why it is important to know how an astrophysical object evolves in function of redshift? I was seeing an &quot;cosmological time per redshift galaxies formation plot&quot; and thinking why redshift and not, who knows, density?
Redshifts are plotted because usually that is all that can be measured.
Other quantities could be plotted, but since these are inferred from the redshift itself (e.g. density would just mean plotting $(1+z)^3$), or would need to assume particular cosmological models or parameters (e.g. if you plotted look-back time), then it makes sense to stick with plotting the observed data.