About 30-50 fields with an exposure time close to the median exposure
of all XMM pointings are necessary for this class. This program is
very similar in scope to the RIXOS project, but with a considerably
larger source density.
The RIXOS experience shows that it is advisable to select fields which have a significantly lower
sensitivity threshold than the flux limit aimed for. This way the
Eddington bias is minimized, the source positions errors are minimized
and all sources in the survey sample have significant X-ray
information (spectra, time variability, extent).
Unlike RIXOS, however, the availability of modern optical
instrumentation will make the bulk of this project a relatively easy
task.
Wide-field imaging instruments are available which will cover
the XMM fields in one go. In order to take advantage of the facilities that
will eventually be available in both hemispheres, the
target fields will be distributed over the whole sky.
The spectroscopic follow-up can ideally be initiated with existing wide-field multifibre instruments (e.g. on the AAT and the WHT). For emission-line objects these reach about ~22m in a 2 hour exposure. We will probably need 2 different exposures per field in order to cope with close candidate counterparts. Assuming 3-4 hours per field in total including setup, we need a total of about 20-25 nights on 4m-class telescopes.
Those counterparts which turn out fainter than the fibre limit will have to be followed up later, e.g. with individual exposures or multislit exposures from 4-8m class telescopes. For distant cluster candidates it will also be interesting to make integral-field spectroscopy.
Last modified 26th August 1999
Text based on AXIS proposal by X.Barcons and the SSC consortium.
Page designed by J.Verdon
www_astro@mssl.ucl.ac.uk