English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Clusters of galaxies are powerful probes with which to study cosmology andastrophysics. However, for many applications an accurate measurement of acluster's mass is essential. A systematic underestimate of hydrostatic massesfrom X-ray observations (the so-called hydrostatic bias) may be responsible fortension between the results of different cosmological measurements. We compareX-ray hydrostatic masses with masses estimated using the caustic method (basedon galaxy velocities) in order to explore the systematic uncertainties of bothmethods and place new constraints on the level of hydrostatic bias. Hydrostaticand caustic mass profiles were determined independently for a sample of 44clusters based on Chandra observations of clusters from the Hectospec ClusterSurvey. This is the largest systematic comparison of its kind. Masses werecompared at a standardised radius ($R_{500}$) using a model that includespossible bias and scatter in both mass estimates. The systematics affectingboth mass determination methods were explored in detail. The hydrostatic masseswere found to be systematically higher than caustic masses on average, and wefound evidence that the caustic method increasingly underestimates the masswhen fewer galaxies are used to measure the caustics. We limit our analysis tothe 14 clusters with the best-sampled caustics where this bias is minimised($\ge210$ galaxies), and find that the average ratio of hydrostatic to causticmass at $R_{500}$ is $M_X/M_C=1.12^{+0.11}_{-0.10}$. We interpret this resultas a constraint on the level of hydrostatic bias, favouring small or zerolevels of hydrostatic bias (less than $20\%$ at the $3\sigma$ level). However,we find systematic uncertainties associated with both mass estimation methodsremain at the $10-15\%$ level, which would permit significantly larger levelsof hydrostatic bias.

Chandra follow up of the Hectospec Cluster Survey: Comparison of Caustic and Hydrostatic Masses and Constraints on the Hydrostatic Bias