The XXL Survey. XXXVIII. Scatter and correlations of X-ray proxies in the bright XXL cluster sample
Abstract
Context. Scaling relations between cluster properties embody the formation and evolution of cosmic structure. Intrinsic scatters and correlations between X-ray properties are determined from merger history, baryonic processes, and dynamical state.
Aims: We look for an unbiased measurement of the scatter covariance matrix among the three main X-ray observable quantities attainable in large X-ray surveys: temperature, luminosity, and gas mass. This also gives us the cluster property with the lowest conditional intrinsic scatter at fixed mass.
Methods: Intrinsic scatters and correlations can be measured under the assumption that the observable properties of the intra-cluster medium hosted in clusters are log-normally distributed around power-law scaling relations. The proposed method is self-consistent, based on minimal assumptions, and requires neither external calibration by weak lensing, or dynamical or hydrostatic masses, nor the knowledge of the mass completeness.
Results: We analysed the 100 brightest clusters detected in the XXL Survey and their X-ray properties measured within a fixed radius of 300 kpc. The gas mass is the less scattered proxy (∼8%). The temperature (∼20%) is intrinsically less scattered than the luminosity (∼30%), but it is measured with a larger observational uncertainty. We found some evidence that gas mass, temperature, and luminosity are positively correlated. Time evolutions are in agreement with the self-similar scenario, but the luminosity-temperature and the gas mass-temperature relations are steeper. Conclusion. Positive correlations between X-ray properties can be determined by the dynamical state and the merger history of the halos. The slopes of the scaling relations are affected by radiative processes.
- Publication:
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Astronomy and Astrophysics
- Pub Date:
- December 2019
- DOI:
- 10.1051/0004-6361/201628521
- arXiv:
- arXiv:1906.10455
- Bibcode:
- 2019A&A...632A..54S
- Keywords:
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- surveys;
- X-rays: galaxies: clusters;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- 19 pages, in press on Astronomy and Astrophysics