MAMPOSSt: Modelling Anisotropy and Mass Profiles of Observed Spherical Systems – I. Gaussian 3D velocities

By G. Mamon, A. Biviano, Gwenael Bou'e Iap, París, Oats, Trieste, U. Chicago. 2012

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Mass modelling of spherical systems through internal motions is hampered by the mass/velocity anisotropy (VA) degeneracy inherent in the Jeans equation, as well as the lack of techniques that are both fast and adaptable to realistic systems. A new fast method, called MAMPOSSt, which performs a maximum likelihood fit of the distribution of observed tracers in projected phase space, is developed and thoroughly tested. MAMPOSSt assumes a shape for the gravitational potential, but instead of postulating a shape for the distribution function in terms of energy and angular momentum, or supposing Gaussian line-of-sight velocity distributions, MAMPOSSt assumes a VA profile and a shape for the 3D velocity distribution, here Gaussian. MAMPOSSt requires no binning, differentiation, nor extrapolation of the observables. Tests on cluster-mass haloes from LambdaCDM cosmological simulations show that, with 500 tracers, MAMPOSSt is able to jointly recover the virial radius, tracer scale radius, dark matter scale radius and outer or constant VA with small bias (<10% on scale radii and <2% on the two other quantities) and inefficiencies of 10%, 27%, 48% and 20%, respectively. MAMPOSSt does not perform better when some parameters are frozen, and even worse when the virial radius is set to its true value, which appears to be the consequence of halo triaxiality. The accuracy of MAMPOSSt depends weakly on the adopted interloper removal scheme, including an efficient iterative Bayesian scheme that we introduce here, which can directly obtain the virial radius with as good precision as MAMPOSSt. Our tests show that MAMPOSSt with Gaussian 3D velocities is very competitive with, and up to 1000x faster than other methods. Hence, MAMPOSSt is a very powerful and rapid tool for the mass and anisotropy modeling of systems such as clusters and groups of galaxies, elliptical and dwarf spheroidal galaxies.

Subfields: Astronomy and Astrophysics, Statistical and Nonlinear Physics

View Paper: https://www.semanticscholar.org/paper/6ea16a97aeb370a1ce0fbfc8ef945fffa08cc4cc

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Citations in the corpus

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): “…estimate itself using thecMr of Macciò et al. (2008), and (iii) the velocity anisotropy profile is that of Mamon & Łokas (2005) with a scale radius identical to that of the NFW profile (as found in cluster-mass halos extracted from cosmological numericals mulations, see Mamon et al. 2010, 2013).”
Galaxy Masses: A Review (2013, methodology): “The bias in the recovered M200 correlates with the ratio of LOS velocity dispersion measured within the virial sphere, estimated along the LOS to that measured in 3D (corrected by √ 3) so that the limiting factor for accurate mass measurements is the triaxiality of ΛCDM halos (Mamon et al. 2013).”
GASP. I. Gas Stripping Phenomena in Galaxies with MUSE (2017, methodology): “Cluster mass and radius are estimated from the dynamical analysis of A. Biviano et al. (2017, in preparation) with the MAMPOSSt technique (Mamon et al. 2013) as =M200 ´- + ☉M1.”