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A ROSAT PSPC investigation of NGC 1399: cold gas and cooling flows in elliptical galaxies

1995; Oxford University Press; Volume: 272; Issue: 3 Linguagem: Inglês

10.1093/mnras/272.3.665

1365-2966

F. V. N. Rangarajan, A. C. Fabian, W. Forman, C. Jones,

Phase Equilibria and Thermodynamics

ROSAT PSPC observations of the Fornax cluster reveal an isothermal gaseous medium at radii from 10 to 330 kpc, with a temperature of 1.1±0.1 keV using Raymond-Smith (RS) models and 0.9±0.1 keV using Mewe-Kaastra (MEKA) models. Within 10 kpc the temperature falls to 0.85 keV (RS) or 0.6 keV (MEKA). The surface brightness is well fitted by a cooling flow model with a mass deposition rate of at least 2 M⊙ yr-1, mostly within the galaxy itself. The abundance is consistent with solar, and the mass of hot X-ray-emitting gas out to 46 kpc is over 1010 M⊙. The MEKA models show clear evidence of an absorbing column density greater than 1021 cm-2 in the centre of NGC 1399, and the variation of column density with radius implies a mass of cold gas in the galaxy of 1.6×1010 M⊙ within 40 kpc, and a mass deposition profile |$\dot M\propto r$|⁠. Within 10 kpc of the centre of NGC 1399, the mean density of cold absorbing gas is similar to that of the hot gas. Using a deprojection method, the density and pressure in the gas are calculated, and other physical parameters of the gas derived. This combination of analyses is used to constrain the gaseous history of NGC 1399. We set a limit on athe X-ray flux of the radio source.