Day 74

Friday.  Was at ETH today, talked to Adam and Alexandre and Simon (Lilly).


Paper recommended by Kravtsov for our SMCluster paper:
1102.2903
X-ray mass proxies from hydrodynamic simulations of galaxy clusters (paper I)
Fabian, Borgani, Rasia, Bonafede, Dolag, Murante, Tornatore


Detailed study of scaling relations between total cluster mass and 3 mass proxies (Tx, Mgas and Yx).  Hydro sim with 140 clusters above 5e13M_sun/h (30 above 1e15Msun/h).  Simulation include (i) non-radiative physics, and (ii) cooling, SF, chemical enrichment and SNe feedback of galactic ejecta.  Large (?) statistic used to quantify robustness of scaling relations, determine z evolution, and *** calibrate intrinsic scatter ***.  Use 18 halos above 5e13Msun/h to test robustness of mass proxies against changing the physical processes in the simulation: Find M-Yx scaling relation to be the least sensitive to variations of the ICM physics; slope and redshift evolution close to self-similar model predictions.  Distribution of the scatter around the best-fitting relation is close to log-normal.  M_gas has the smallest scatter in mass (sigma_lnM=0.04-0.06), with mild dependence on the redshift.  M-T relation is the one with the largest scatter, with sigma_lnM > 0.1 at z=0, increasing to >0.15 at z=1.  The intrinsic scatter in the M-Yx relation is slightly larger than in the M-M_gas relation.  These results confirm that both Yx and M_gas mass proxies are well suited for cosmological applications of future large X-ray surveys.


* self-similar model?  ...need to study this


1011.1681
On the accuracy of weak lensing cluster mass reconstructions
Becker, Kravtsov


Scatter in the WL massing derived using the NFW fitting method has irreducible contributions from the triaxial shapes of cluster-sized halos and uncorrelated large-scale matter projections along the LOS.  Correlated LSS within several virial radii of clusters contributes a smaller amound to the scatter.  The intrinsic scatter due to physical sources os 20% for massive clusters, and as high as 30% for group-sized systems.  For ground-based observations, the total scatter should be dominated by shape noise in galaxies used to measure the shear.  WL mass measurements can have 5-10% bias.  Robust calibration of the bias requires detailed simulations which include more observational effects than considered here.  *** Such calibration exercise needs to be carried out for each specific WL mass estimation method ***, as the details of the method determine in part the expected scatter and bias.  Present iterative method for estimating M500c that can eliminate the bias for analysis of ground-based data.


MNRAS2011...416...1392G
Optimizing weak lensing mass estimates from cluster profile uncertainty
Gruen, Bernstein, Lam, Seitz


Use N-body simulated haloes to derive and evaluate a WL circular aperture mass measurement Map that minimizes the mass estimate variance <(Map-M200m)^2> in the presences of shape noise, LOS structure, variation in cluster structure (concentration, asphericity, substructure).  The resulting mass estimator improves on Map filters [to some ambiguous extent].  Optimizing for uncorrelated LSS while ignoring the variation of internal cluster structure puts too much weight on the profile near the core of haloes, and could be worse than not accounting for LSS at all.  We briefly discuss the impact of variability in cluster structure and correlated structures on the design and performance of WL surveys intended to calibrate cluster MORs.