A Question On Redshift

[elliottmarter]

A redshift survey has identified a galaxy cluster for which it infers a di stance of 520 Mpc. At what redshift is this cluster observed to be? You may use H0 = 72 km s−1 Mpc−1

Now call me old fashioned but don't i need some kind of relativistic speed to calculate the redshift, i mean i have a distance of 520Mpc (=16.12x10^21m) and the Hubble constant...but I am sure i need a value for how fast its traveling away from me...

Thanks

EDIT i think i just realized that i times its distance by Ho to get its speed as its Kms-1 Mpc-1

 

[nickjer]

Your edit is correct.

 

[mgb_phys]

Then as long as this speed is much less than 'c' you can just use classical redshift.
When you get redshifts approaching (or larger than) 1 you need to take into account the expansion of the universe.

 

[elliottmarter]

yeah the Lorentz factor was 1.00... so i just used z=v/c