Comparison of simple mass estimators for slowly rotating elliptical galaxies

Abstract

We compare the performance of mass estimators for elliptical galaxies that rely on the directly observable surface brightness and velocity dispersion profiles, without invoking computationally expensive detailed modeling. These methods recover the mass at a specific radius where the mass estimate is expected to be least sensitive to the anisotropy of stellar orbits. One method (Wolf et al. 2010) uses the total luminosity-weighted velocity dispersion and evaluates the mass at a 3D half-light radius $r_{1/2}$, i.e., it depends on the GLOBAL galaxy properties. Another approach (Churazov et al. 2010) estimates the mass from the velocity dispersion at a radius $R_2$ where the surface brightness declines as $R^{-2}$, i.e., it depends on the LOCAL properties. We evaluate the accuracy of the two methods for analytical models, simulated galaxies and real elliptical galaxies that have already been modeled by the Schwarzschild's orbit-superposition technique. Both estimators recover an almost unbiased circular speed estimate with a modest RMS scatter ($\lesssim 10\%$). Tests on analytical models and simulated galaxies indicate that the local estimator has a smaller RMS scatter than the global one. We show by examination of simulated galaxies that the projected velocity dispersion at $R_2$ could serve as a good proxy for the virial galaxy mass. For simulated galaxies the total halo mass scales with ${\sigma }_p(R_2)$ as $M_{vir}\left[M_{\odot }{h}^{-1}\right]\approx 6\cdot 10^{12}{\left(\frac{{\sigma }_p(R_2)}{200\mathrm{km}{\mathrm{s}}^{-1}}\right)}^4$ with RMS scatter $\approx 40\%$.

arXiv comment19 pages, 14 figures, 4 tables, accepted for publication in MNRAS

References in corpus (29)

• The M-sigma and M-L Relations in Galactic Bulges and Determinations of their Intrinsic Scatter
• The SAURON project - IV. The mass-to-light ratio, the virial mass estimator and the fundamental plane of elliptical and lenticular galaxies
• Structure and Formation of Elliptical and Spheroidal Galaxies
• The Two Phases of Galaxy Formation
• The ATLAS3D project - III. A census of the stellar angular momentum within the effective radius of early-type galaxies: unveiling the distribution of Fast and Slow Rotators
• Accurate masses for dispersion-supported galaxies
• Dynamical family properties and dark halo scaling relations of giant elliptical galaxies
• The cosmological size and velocity dispersion evolution of massive early-type galaxies
• Axisymmetric Dynamical Models of the Central Regions of Galaxies
• The Assembly of Galaxies in a Hierarchically Clustering Universe
• Dynamical modelling of luminous and dark matter in 17 Coma early-type galaxies
• Dynamical masses of early-type galaxies: a comparison to lensing results and implications for the stellar IMF and the distribution of dark matter
• Dynamical Measurements of Black Hole Masses in Four Brightest Cluster Galaxies at 100 Mpc
• Dynamical modelling of stars and gas in NGC2974: determination of mass-to-light ratio, inclination and orbital structure by Schwarzschild's method
• The Influence of Dark Matter Halos on Dynamical Estimates of Black Hole Mass: Ten New Measurements for High-sigma Early-Type Galaxies
• Galaxy Kinematics with VIRUS-P: The Dark Matter Halo of M87
• The Dynamical Fingerprint of Core Scouring in Massive Elliptical Galaxies
• Regularized orbit models unveiling the stellar structure and dark matter halo of the Coma elliptical NGC 4807
• Orbit-based dynamical models of the Sculptor dSph galaxy
• Recovering the intrinsic shape of early-type galaxies
• The mass and angular momentum distribution of simulated massive early-type galaxies to large radii
• On the deprojection of axisymmetric bodies
• Comparison of an approximately isothermal gravitational potentials of elliptical galaxies based on X-ray and optical data
• The flattening and the orbital structure of early-type galaxies and collisionless N-body binary disk mergers
• Axisymmetric orbit models of N-body merger remnants: a dependency of reconstructed mass on viewing angle
• Can we measure the slopes of density profiles in dwarf spheroidal galaxies?
• The Effect of Spatial Gradients in Stellar Mass-to-Light Ratio on Black Hole Mass Measurements
• Testing a simple recipe for estimating galaxy masses from minimal observational data
• Stellar kinematics of X-ray bright massive elliptical galaxies

Cited by in corpus (4)

• Knowing the unknowns: uncertainties in simple estimators of galactic dynamical masses
• Multiple Chemodynamic Stellar Populations of the Ursa Minor Dwarf Spheroidal Galaxy
• $R_{\mathrm{e}}$. I. Understanding galaxy sizes, associated luminosity densities, and the artificial division of the early-type galaxy population
• Mass density slope of elliptical galaxies from strong lensing and resolved stellar kinematics