ROSAT PSPC SPECTRA OF X-RAY-SELECTED NARROW-EMISSION-LINE GALAXIES

We analyse the ROSAT PSPC spectra of 19 X-ray-selected narrow-emission -line galaxies (NELGs) discovered during the optical identification of sources in the ROSAT UK Deep Survey. Their properties are compared wi th those of broad-line active galactic nuclei (AGN) in the same sample . Counts in three spectral bands have been extracted for all the sourc es, and have been fitted with a power-law model assuming the Galactic value for N-H. The average slope of the NELGs is alpha = 0.45 +/- 0.09 , whilst for the AGN it is alpha = 0.96 +/- 0.03. The power-law model is a good fit for similar to 90 per cent of NELGs and similar to 75 pe r cent of AGN. Recent work shows that the fractional surface density o f NELGs increases with respect to AGN at faint fluxes. Thus they are e xpected to be an important component of the residual soft (< 2 keV) X- ray background. The slope of the X-ray background (alpha similar to 0. 4, 1-10 keV) is harder than that of AGN (alpha similar to 1) but our r esults show that it is consistent with the summed spectrum of the NELG s in the deep survey (alpha similar to 0.4). This may finally reconcil e the spectrum of the background with the properties of the sources th at constitute it.