Nick Seymour

XMM–Newton 13H deep field – I. X-ray sources

We present the results of a deep X-ray survey conducted with XMM‐Newton, centred on the UK ROSAT 13 H deep field area. This region covers 0.18 deg 2 , and is the first of the two areas covered with XMM‐Newton as part of an extensive multiwavelength survey designed to study the nature and evolution of the faint X-ray source population. We have produced detailed Monte Carlo simulations to obtain a quantitative characterization of the source detection procedure and to assess the reliability of the resultant sourcelist. We use the simulations to establish a likelihood threshold, above which we expect less than seven (3 per cent) of our sources to be spurious. We present the final catalogue of 225 sources. Within the central 9 arcmin, 68 per cent of source positions are accurate to 2 arcsec, making optical follow-up relatively straightforward. We construct the N (>S) relation in four energy bands: 0.2‐0.5, 0.5‐2, 2‐5 and 5‐10 keV. In all but our highest energy band we find that the source counts can be represented by a double power law with a bright-end slope consistent with the Euclidean case and a break around 10 −14y erg cm −2 s −1 . Below this flux, the counts exhibit a flattening. Our source counts reach densities of 700, 1300, 900 and 300 deg −2 at fluxes of 4.1 × 10 −16 , 4.5 × 10 −16 , 1.1 × 10 −15 and 5.3 × 10 −15 erg cm −2 s −1 in the 0.2‐0.5, 0.5‐2, 2‐5 and 5‐10 keV energy bands, respectively. We have compared our source counts with those in the two Chandra deep fields and Lockman hole, and found our source counts to be amongst the highest of these fields in all energy bands. We resolve >51 per cent (>50 per cent) of the X-ray background emission in the 1‐2 keV (2‐5 keV) energy bands. Ke yw ords: surveys ‐ galaxies: active ‐ quasars: general ‐ X-rays: galaxies.

CONSISTENCY BETWEEN THE RADIO & MIR SOURCE COUNTS USING THE RADIO-MIR CORRELATION

We show from the recent extrapolation of the radio-FIR correlation to the MIR that the 20 cm and 15 um differential source counts are likely to come from the same parent population.

Radio observations of the 13hXMM-Newton/ROSATDeep X-ray Survey Area

In order to determine the relationship between the faint X-ray and faint radio source populations, and hence to help understand the X-ray and radio emission mechanisms in those faint source populations, we have made a deep 1.4-GHz Very Large Array radio survey of the 13 h + 38° XMM-Newton/ROSAT X-ray Survey Area. From a combined data set of 10-h, B-configuration data and 14-h, A-configuration data, maps with 3.35-arcsec resolution and a noise limit of 7.5 μJy were constructed. A complete sample of 449 sources was detected within a 30-arcmin diameter region above a 4a detection limit of 30 μJy, at the map centre, making this one of the deepest radio surveys at this frequency. The differential source count shows a significant upturn at submilliJansky flux densities, similar to that seen in other deep surveys at 1.4 GHz (e.g. the Phoenix survey), but larger than that seen in the Hubble Deep Field (HDF) which may have been selected to be underdense. This upturn is well modelled by the emergence of a population of medium-redshift star-forming galaxies which dominate at faint flux densities. The brighter source counts are well modelled by active galactic nuclei.