SIMBAD references

We present a deep X-ray ROSAT/HRI observation of the rich lensing cluster Abell 2390 as well as the analysis of the gas and matter distribution in the cluster. The X-ray centroid coincides with the location of the central cD galaxy, and the core appears to be dominated by a massive cooling flow, one of the strongest ever studied. On larger scales, the X-ray distribution is elliptical and locally distorted by a significant "sub-structure", which is located some 100 h^–1 kpc from the center. The mass of this sub-structure is estimated to be ∼ 1/15 of the total cluster mass and appears to be associated with an enhancement in the galaxy distribution, in the region where the giant "straight arc" and several arclets are observed. A simple lens model based on the geometrical properties of the X-ray gas shows that this sub-structure allows a simple explanation of the peculiar shape of the arc and puts strong constraints on the total mass distribution in the central part of this cluster. The derived M/L in the central part of the cluster is found to be around 250 in solar units, a rather common value compared with other cluster-lenses. Moreover, the link between the matter distribution derived from the lens model and the density profile obtained from the X-ray map analysis is used to infer the temperature profile in the cluster. This profile shows a significant decrease near the center, in agreement with the existence of the cooling flow. Both X-ray and lensing constraints are combined together to give a consistent picture of the dynamics of the central part of A2390.