Testing a simple recipe for estimating galaxy masses from minimal observational data

The accuracy and robustness of a simple method to estimate the total mass profile of a galaxy are tested using a sample of 65 cosmological zoom simulations of individual galaxies. The method only requires information on the optical surface brightness and the projected velocity dispersion profiles, and therefore can be applied even in the case of poor observational data. In the simulated sample, massive galaxies (σ≃ 200–400 km s−1) at redshift z= 0 have almost isothermal rotation curves for broad range of radii (rms ≃ 5 per cent for the circular speed deviations from a constant value over 0.5Reff 6.5 × 1012 M⊙) and the HE estimate is biased low by ≃ 3–4 per cent, which can be traced to the presence of gas motions. This implies that the simple mass estimate can be used to determine the mass of observed massive elliptical galaxies to an accuracy of 5–8 per cent and can be very useful for galaxy surveys.