Determine galaxy cluster peculiar velocities beyond the nearby Universe

Determine the peculiar velocity distribution of galaxy clusters beyond the nearby Universe to quantitatively account for the contribution of peculiar motions to redshift-based distance uncertainties used in SRG/eROSITA supercluster identification and reliability assessments.

Background

In estimating supercluster reliability, the authors vary cluster redshifts within their uncertainties and explicitly add a peculiar velocity component because cluster peculiar motions contribute to redshift-based distance errors.

They adopt a typical value of 400 km/s for cluster peculiar velocities due to the lack of robust constraints outside the local Universe, noting that this limitation impacts the accuracy of supercluster distance estimates and reliability calculations.

References

The peculiar velocities of clusters are not well-constrained, except for the very nearby Universe.

— The SRG/eROSITA All-Sky Survey: First catalog of superclusters in the western Galactic hemisphere  (2402.08454 - Liu et al., 2024) in Section 3 (Supercluster identification), paragraph on redshift uncertainties and peculiar velocities