On the efficiency and reliability of cluster mass estimates based on member galaxies

By A. Biviano, Giuseppe Murante, Stefano Borgani, A. Diaferio, Klaus Dolag, M. Girardi. 2006

194 citations recorded by the source corpus.

Aims. We study the efficiency and reliability of cluster mass estimators that are based on the projected phase-space distribution of galaxies in a cluster region. Methods. We analyse a data-set of 62 clusters extracted from a concordance Λ CDM cosmological hydrodynamical simulation. We consider both dark matter (DM) particles and simulated galaxies as tracers of the clusters gravitational potential. Two cluster mass estimators are considered: the virial mass estimator, corrected for the surface-pressure term, and a mass estimator (that we call $M_{\sigma}$) based entirely on the velocity dispersion estimate of the cluster. In order to simulate observations, galaxies (or DM particles) are first selected in cylinders of given radius (from 0.5 to 1.5 h -1 Mpc) and $\simeq$$200h^{-1}$ Mpc length. Cluster members are then identified by applying a suitable interloper removal algorithm. Results. The virial mass estimator overestimates the true mass by $\simeq$10% on average, for sample sizes of $\ga$60 cluster members. For similar sample sizes, $M_{\sigma}$ underestimates the true mass by $\simeq$15%, on average. For smaller sample sizes, the bias of the virial mass estimator substantially increases, while the $M_{\sigma}$ estimator becomes essentially unbiased. The dispersion of both mass estimates increases by a factor ~2 as the number of cluster members decreases from ~400 to ~20. It is possible to reduce the bias in the virial mass estimates either by removing clusters with significant evidence for subclustering or by selecting early-type galaxies, which substantially reduces the interloper contamination. Early-type galaxies cannot however be used to improve the $M_{\sigma}$ estimates since their intrinsic velocity distribution is slightly biased relative to that of the DM particles. Radially-dependent incompleteness can drastically affect the virial mass estimates, but leaves the $M_{\sigma}$ estimates almost unaffected. Other observational effects, like centering and velocity errors and different observational apertures, have little effect on the mass estimates.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/623916b4d6f121be2f591589bfbddaf6aa9a5fc8

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Citations in the corpus

The relation between velocity dispersion and mass in simulated clusters of galaxies: dependence on the tracer and the baryonic physics (2013, methodology): “…(e.g. Arnaud et al. 2010; Williamson et al. 2011; Kay et al. 2012) observations, the optical luminosity or richness traced by the cluster galaxy population (e.g. Popesso et al. 2007; Rozo et al. 2009), and velocity dispersion of member galaxies (e.g. Biviano et al. 2006; Saro et al. 2012).”
Galaxy Zoo: the dependence of morphology and colour on environment (2008, background): “2 of Biviano et al. 2006) there is no mass-dependence of the star-forming fraction, while below this there is a clear dependence.”
CLASH-VLT: The mass, velocity-anisotropy, and pseudo-phase-space density profiles of the z = 0.44 galaxy cluster MACS J1206.2-0847 (2013, methodology): “Other causes that lead Ebeling et al. (2009) to overestimate the cluster mass using the virial theorem are the negl ct of the surface-pressure term (The & White 1986), and the use of a spatially incomplete sample in the estimate of the projected harmonic mean radius (see Biviano et al. 2006).”
Virial Scaling of Massive Dark Matter Halos: Why Clusters Prefer a High Normalization Cosmology (2007, methodology): “An effect of this magnitude appears unlikely from line-of-sight projection effects alone (Biviano et al. 2006; Becker et al. 2007).”
MAMPOSSt: Modelling Anisotropy and Mass Profiles of Observed Spherical Systems – I. Gaussian 3D velocities (2012, methodology): “…dHK) of den Hartog & Katgert (1996), a widely used procedure that works reasonably well on clustermass haloes from cosmological simulations (Biviano et al. 2006; Wojtak et al. 2007), despite its crude underlying physics; (ii) the method (hereafter, KBM) of Katgert, Biviano, & Mazure (2004,…”