SPECTRAL AND SPATIAL-ANALYSIS OF THE INTRAGROUP MEDIUM IN THE NGC-2300 GROUP

We report the results of spectral and spatial analysis of three overla pping ROSAT PSPC observations of the NGC 2300 group. Spatial analysis of the co-added fields reveals that the diffuse X-ray gas can be trace d to at least 25' (0.33 Mpc, H-0 = 50 km s(-1) Mpc(-1)). The surface b rightness of the gas is well fitted with an isothermal King model with a core radius of 4'.28(-0.93)(+1.27) (56.5(-12.3)(+16.8) kpc) and a b eta of 0.410(-0.021)(+0.027) The temperature of the gas, as determined from fitting a Raymond-Smith plasma model to the spectral data, is 0. 971(-0.08)(+0.11)keV. The additional exposure time obtained allows thr ee different annuli to be fitted. Fitting these different regions cons trains any temperature gradient to be less than similar to 0.2 keV. Th e abundance determined from the X-ray spectrum is also low-less than 0 .11 solar. The mass of gas within 0.33 Mpc is 1.25 x 10(12) M., and if the gas is in hydrostatic equilibrium with the potential the total ma ss within this radius is 1.47 x 10(13) M.. Comparing the mass of the g alaxies plus the mass of hot gas to the total mass of the system yield s an observed baryonic fraction of 10%-16%. This value is higher than our original analysis, where the form of the gas density profile was f ixed at an assumed value. We also discuss the abundance of the diffuse gas and how the evolution of the elliptical galaxy is expected to aff ect the gas.