Spectral and spatial analysis of the intragroup medium in the NGC 2300 group

David S. Davis, John S. Mulchaey, Richard F. Mushotzky, David Burstein

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We report the results of spectral and spatial analysis of three overlapping ROSAT PSPC observations of the NGC 2300 group. Spatial analysis of the co-added fields reveals that the diffuse X-ray gas can be traced to at least 25′ (0.33 Mpc, H0 = 50 km s-1 Mpc-1). The surface brightness 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 β 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 0.97-0.08+0.11 keV. The additional exposure time obtained allows three different annuli to be fitted. Fitting these different regions constrains any temperature gradient to be less than ∼0.2 keV. The 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 × 1012 M, and if the gas is in hydrostatic equilibrium with the potential the total mass within this radius is 1.47 × 1013 M. Comparing the mass of the galaxies plus the mass of hot gas to the total mass of the system yields an observed baryonic fraction of 10%-16%. This value is higher than our original analysis, where the form of the gas density profile was fixed at an assumed value. We also discuss the abundance of the diffuse gas and how the evolution of the elliptical galaxy is expected to affect the gas.

Original languageEnglish
Pages (from-to)601-611
Number of pages11
JournalAstrophysical Journal
Issue number2 PART I
StatePublished - 1996
Externally publishedYes


  • Diffuse radiation
  • Galaxies: clusters: individual (NGC-2300)
  • Intergalactic medium
  • X-rays: galaxies


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