Oral Presentation
Quantifying and explaining scatter in the X-ray luminosity - halo mass relation
Presenter: Joey Braspenning (Max Planck Institute for Astronomy)
Though galaxy clusters are massive objects, dominated by gravity, there is significant scatter in their integrated properties. Different reasons have been proposed to explain this, such as assembly bias, AGN feedback or environmental effects. We, for the first time, quantify the scatter in cluster scaling relations over 2 orders of magnitude in mass using more than a million objects from the FLAMINGO simulations. We provide fitting functions for the scaling relations with mass and redshift, and find that a broken power law accurately describes the scatter-mass relations, with the break shifting to lower masses when redshift increases.
We proceed to investigate the origin of the scatter in narrow mass bins of <0.05 dex. Our results show that an independent measurement of the SZ signal can reduce the scatter in the X-ray luminosity-mass scaling relation by 50% without a reduction in sample size. This is in stark contrast to other methods of reducing scatter, which rely on creating “clean” samples, often reducing the sample size by more than half. We find that other methods, such as merger time, dark matter concentration, or black hole mass do not result in any reduction in scatter. In total we have checked the reduction in scatter using 25 different probes. This opens the way to a low-scatter sample of X-ray luminosity clusters which can be used for cosmology. On top of that, our fits to the scatter with mass and redshift can directly be input into cosmological parameter inference pipelines using galaxy groups and clusters.
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