The total mass of the early-type galaxy NGC 4649 (M60)

In this paper we analyze the problem of the total mass and the total mass-to-light ratio of the early-type galaxy NGC 4649 (M60). We have used two independent techniques: the X-ray methodology which is based on the temperature of the X-ray halo of NGC 4649 and the tracer mass estimator (TME) which uses globular clusters (GCs) observed in this galaxy. We calculated the mass in Newtonian and MOdified Newtonian Dynamics (MOND) approaches and found that interior to 3 effective radii (Re) there is no need for large amounts of dark matter. Beyond 3Re dark matter starts to play important dynamical role. We also discuss possible reasons for the discrepancy between the estimates of the total mass based on X-rays and TME in the outer regions of NGC 4649.Comment: Accepted by Serbian Astronomical Journal, 8 pages, 1 figur

Flattened Galactic Haloes and Baryonic Dark Matter

We discuss the tight interconnection between microlensing optical depths, flattening of dark haloes and low-to-intermediate redshift baryonic census. By analysing plots of the microlensing optical depth as a function of galactic coordinates for different values of axis ratio $q$ of the galactic MACHO halo, we have shown that observations are best described by a flattened halo with $q \simeq 0.6$. There is no dynamical obstacle for such a choice of global halo shape. Both extremely flattened $q \simeq 0.2$ and spherical $q \simeq 1$ haloes have several difficulties, although not of equal severity. Consequences of such flattening for the cosmological density fraction contained in MACHOs are considered and comparison with mass in low and intermediate-redshift Ly$\alpha$ forest and other plausible reservoirs of gas is discussed in context of a unified description of the evolution of baryonic content of the universe.Comment: 14 pages, 15 figures, TeX, uses mn.tex and psfig.tex, MNRAS accepte