Effects of selection and covariance on X-ray scaling relations of galaxy clusters
Abstract
We explore how the behaviour of galaxy cluster scaling relations are affected by flux-limited selection biases and intrinsic covariance among observable properties. Our models presume log-normal covariance between luminosity (L) and temperature (T) at fixed mass (M), centred on evolving, power-law mean relations as a function of host halo mass. Selection can mimic evolution; the L-M and L-T relations from shallow X-ray flux-limited samples will deviate from mass-limited expectations at nearly all scales while the relations from deep surveys (10-14ergs-1cm-2) become complete, and therefore unbiased, at masses above ~2 × 1014h-1Msolar. We derive expressions for low-order moments of the luminosity distribution at fixed temperature, and show that the slope and scatter of the L-T relation observed in flux-limited samples is sensitive to the assumed L-T correlation coefficient. In addition, L-T covariance affects the redshift behaviour of halo counts and mean luminosity in a manner that is nearly degenerate with intrinsic population evolution.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- January 2008
- DOI:
- 10.1111/j.1745-3933.2007.00407.x
- arXiv:
- arXiv:0706.2189
- Bibcode:
- 2008MNRAS.383L..10N
- Keywords:
-
- galaxies: clusters: general;
- X-rays: galaxies: clusters;
- Astrophysics
- E-Print:
- 5pages, 4 Figures, Submitted to MNRAS