We present the analysis of a deep ( 167 ks ) ROSAT HRI observation of the cD galaxy NGC 1399 in the Fornax cluster , comparing it with previous work on this galaxy and with recent Chandra data .
We find , in agreement with previous observations , an extended and asymmetric gaseous halo with a luminosity ( in the 0.1-2.4 keV energy band ) of L _ { X } = ( 5.50 \pm 0.04 ) \times 10 ^ { 41 } erg s ^ { -1 } within 46 kpc ( assuming a distance of D=19 Mpc ) .
Using both HRI and , at larger radii , archival PSPC data , we find that the radial behavior of the X-ray surface brightness profile is not consistent with a simple Beta model and suggests instead three distinct components .
We use a multi-component bidimensional model to study in detail these three components that we identify respectively with the cooling flow region , the galactic and the cluster halo .
From these data we derive a binding mass distribution in agreement with that suggested by optical dynamical indicators , with an inner core dominated by luminous matter and an extended dark halo differently distributed on galactic and cluster scales .
The HRI data and a preliminary analysis of Chandra public data , allow us to detect significant density fluctuations in the halo .
We discuss possible non-equilibrium scenarios to explain the hot halo structure , including tidal interactions with neighboring galaxies , ram stripping from the intra-cluster medium and merging events .

In the innermost region of NGC 1399 , the comparison between the X-ray and radio emission suggests that the radio emitting plasma is displacing and producing shocks in the hot X-ray emitting gas .
We do not detect the nuclear source in X-rays and we pose an upper limit of \sim 4 \times 10 ^ { 39 } erg s ^ { -1 } ( 0.1-2.4 keV ) to its X-ray luminosity .

We found that the NGC 1404 halo is well represented by a single symmetric Beta model and follows the stellar light profile within the inner 8 kpc .
The mass distribution is similar to the ‘ central ’ component of the NGC 1399 halo .
At larger radii ram pressure stripping from the intra-cluster medium produces strong asymmetries in the gas distribution .

Finally we discuss the properties of the point source population finding evidence of correlation between the source excess and NGC 1399 .