Dynamical state of galaxy clusters in the Roman COSMOS Deep Field
| Program ID | 19087 |
|---|---|
| Science Category | Large Scale Structure of the Universe |
| Program Type | Analysis |
| Category | Small |
| Principal Investigator | Charlie Mpetha |
| PI Institution | NASA Goddard Space Flight Center |
| Co-Investigators |
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| Abstract | Galaxy clusters have a range of dynamical states, from relaxed to unrelaxed. Cluster analyses are complicated by strong effects of dynamical state on cluster mass calibration, thus it is vital we understand the link between the two. Dynamical state can be assessed in multiple ways: through the member galaxy properties in optical, the morphology and peak of the hot gas in X-ray and Sunyaev-Zeldovich (SZ) emission, or the total density profile inferred through the lensing of background galaxies around foreground clusters. The latter method is the only one that probes the total matter distribution (including dark matter), and thus is unbiased. However, we do not have lensing information for the majority of clusters, most of which are observed in the optical. An optical proxy for dynamical state, robustly validated using lensing, would be transformative for cluster science. This is particularly prescient as Stage-IV surveys will greatly increase the number of observed clusters - without correcting for dynamical state mass bias we will not be able to make full use of these observations. The Roman COSMOS Deep Field contains hundreds of clusters, most of which are observed in optical. We will focus on a recently proposed optical proxy for dynamical state found to perform well in simulations, estimating it for all clusters in the field. We will identify massive clusters with multi-wavelength information, measure their X-ray/SZ based dynamical state, and compare them to the optical proxy. Then we will split the total sample into a relaxed and unrelaxed subsample. Using exquisite Roman lensing, we will accurately assess the dynamical state for the individual clusters, and for stacked lensing profiles of the relaxed/unrelaxed samples. From this, we will validate the simple optical proxy. By measuring the mass in the relaxed/unrelaxed sample will will quantify, and develop a method to correct for, the dynamical state mass bias, improving future Roman cluster analyses. |