To be clear, the quoted precision is supported by the individual line measurements. For exampleRobin Leadbeater wrote:
Yes I agree. I made this clear in my post. I agree with you that the quoted absolute accuracy in the paper is not supported by evidence presented there.
Cheers
Robin
"Ra 69 (Tab.4), we derive a mean redshift of z = 0.04360 ± 0.00051" (0.0436 +-0.0005 would be better)
This is reasonable (0.0005 = 150km/s) but there is no evidence presented that this is the absolute accuracy
Cheers
Robin