Improving NASA/IPAC Extragalactic Database Redshift Calculations
  The NASA/IPAC Extragalactic Database (NED) is an impressive tool for finding
near-exhaustive information on millions of astrophysical objects. Here, we
outline a small systematic error that occurs in NED because a low-redshift
approximation is used when making the correction from redshifts in the
heliocentric frame to the cosmic microwave background (CMB) rest frame. It
means that historically NED systematically misreported the values of CMB-frame
redshifts by up to $\sim10^{-3}z$ (about 0.001 at redshift of 1). This is a
systematic error, and therefore the impact on applications requiring precise
redshifts has the potential to be significant -- for example, a systematic
redshift error of $\sim10^{-4}$ at low redshift could resolve the Hubble
tension. We have consulted with the NED team and they are updating the software
to remove this systematic error so these corrections are accurate at all
redshifts. Here, we explain the changes and how they impact the redshift values
NED currently reports.
