XMM-Newton telescope peeks through Lockman hole
EUROPEAN SPACE AGENCY SCIENCE RELEASE
Posted: May 19, 2000
XMM-Newton's observations of the 'Lockman Hole' will eventually accumulate nearly 2 days worth of exposure time, but as a foretaste of the expected results, the first 8 hours of data have been processed. The first two images show the results from each of the XMM EPIC Imaging cameras with 20 000 second exposures (5.5 hours).
While the ROSAT observatory (launched in 1990) previously imaged this field with great sensitivity, it was only able to detect low energy X-rays, whilst most of the flux from distant faint quasars and active galaxies is expected to arrive at higher X-ray energies.
The Italian-Dutch BeppoSAX observatory had previously offered one of the best high-energy X-ray views of the Lockman Hole (image 3). Exposure duration was 112 000 seconds. But the spatial resolution and efficiency of BeppoSAX is dramatically overtaken by the superb quality of XMM-Newton's mirrors and detectors.
With only 1/5 the observation time, XMM-Newton therefore detects many more sources and with much better precision. However, BeppoSAX, launched in 1996, has other unique capabilities - such as the ability to observe X-rays with energies from the lowest observable by XMM-Newton to over 10 times higher - that make it a powerful observatory in its own right.
Another glimpse of the power of XMM-Newton comes by examining what happens when the energies of the X-rays are separated: two further pictures from the Lockman hole observations show the response in the low energy ROSAT band (0,1KeV - 2.5KeV) and the energies above the ROSAT range.
While many sources are found at the same position in the sky in these two pictures, there are subtle differences. For example above centre and to the right, some of the sources bright in the ROSAT band (red and yellow) are hardly visible at higher energies. Conversely, one or two objects are brighter (red) in the high energy picture but more difficult to see at the lowest energies.
Detecting variations such as these will be vital for XMM-Newton's work in distinguishing a suspected population of massive black holes, cloaked in a thick X-ray absorbing ring of gas and dust, lurking in young galaxies far out in the early Universe.
ESA's X-ray space observatory is currently calibrating and verifying the performance of its science instruments before regular science observations start in June.