1999/02/11 by H. Aceves, Aceves, H., J. Perea +1
Physics and Astronomy · #Astrophysics (astro-ph) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #Scientific Research and Discoveries #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/9902166
10 pages & 6 figures, uses epsf.sty. Accepted for publication in A&A
arxiv created 1999/02/11 · openalex publication_date 1999/02/11 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The two most common mass estimators that use velocity dispersions and positions of objects in a stellar system, the virial mass estimator (VME) and the projected mass estimator (PME), are revisited and tested using N-body experiments. We consider here only spherical, isolated, and isotropic velocity dispersion systems. We have found that the PME can overestimate masses by ~ 20%, for realistic cluster mass profiles, if applied only to regions around the total system's "effective" radius. The VME can yield a correct mass at different radii provided that the total potential energy term is correctly taken into account and the system is completely sampled; otherwise, it may lead to similar errors as the PME. A surface pressure (3PV) term recently alluded to be usually neglected when using the VME and therefore required as a correction term is here found not necessarily required, although it can be used to yield a reasonable correction term. The preferred method here, however, is the virial theorem due to its simplicity and better agreement with N-body experiments. The possible reasons for the mass discrepancies found when using the PME and the VME in some N-body simulations are also briefly discussed.