Physical conditions in metal line systems toward Q1037-2704: Evidence for superclustering at z=2

Abstract

We present a high spectral resolution optical spectrum of the bright quasar Q~1037-2704. The large number of absorption systems suggests the presence of an intervening supercluster, but the issue remains controversial.\par We demonstrate that the strong CIV system at z=2.08 spanning more than 1500 km/s is made up of narrow components with typical Doppler parameter b=8 km/s. The gas is probably photo-ionized in which case the photo-ionizing spectrum should be dominated by stellar radiation. Analysis of HI, SiIV, NV and CIV absorptions shows that the gas has a fairly large metal content, Z>0.1Zsolar. We detect CII*1335 absorption in subcomponents of the z=2.133 system, which have moderate total CII column densities implying an electronic density of ne=3/cm3. In addition, the weakness of the OI1302, SiII1304 and FeII1608 lines allows a detailed analysis of the line profiles. The results are that the system has four narrow (b=10km/s) components; the oxygen abundance is of the order of 0.03 solar; the iron abundance is surprisingly large [Fe/O]=[Fe/O]solar+0.3. If photo-ionized by the UV flux from the quasar, the distance between the absorber and the quasar should be larger than 0.3 Mpc. This demontrates that the gas is not associated with the quasar and, together with the detection of eight multiple metal systems between z=1.91 and 2.13, suggests the presence of a coherent structure extended over 80 Mpc along the line of sight.