Features of the Soft X-ray Background and Implications for the EUV Background

A series of eight overlapping ROSAT PSPC observations situated in the Lockman hole region have been analysed in the 0.1 – 0.4 keV band. The total exposure of ~ 137 ks and the ultra-low interstellar column density make the data extremely suitable for studies of the diffuse signal. After excluding the contribution of bright discrete sources the remaining signal was examined on a scale of 20′. As expected the 0.1 – 0.4 keV signal exhibits a strong anticorrelation with column density. However, there is also evidence for significant excess fluctuations superimposed on this anticorrelation which may be attributable to some form of cloud structures within the hot ISM. The diffuse signal expected in the ROSAT WFC all-sky survey for this region is predicted and shown to be far in excess of that observed. The origin of the fluctuations in the soft X-ray background and their possible relevance to the Extreme-Ultraviolet background are discussed.