Cosmology and Astrophysics from Relaxed Galaxy Clusters I: Sample Selection

Understand

This is the first in a series of papers studying the astrophysics and cosmology of massive, dynamically relaxed galaxy clusters.

• Here we present a new, automated method for identifying relaxed clusters based on their morphologies in X-ray imaging data.
• While broadly similar to others in the literature, the morphological quantities that we measure are specifically designed to provide a fair basis for comparison across a range of data quality and cluster redshifts, to be robust against missing data due to point-source masks and gaps between detectors, and to avoid strong assumptions about the cosmological background and cluster masses.
• Based on three morphological indicators - Symmetry, Peakiness and Alignment - we develop the SPA criterion for relaxation.