A first part of the program was performed by the AIP through regular observation proposals submitted to ESO or in Max-Planck time. Images and catalogues obtained in this program are released under the AIP-XMM-WFI label.
A second part of that program was performed as a public imaging survey by the ESO EIS-team. Data were obtained on 12 XMM fields in filters BVRI, all images and the single passband catalogues of the high-latitude fields were released via the ESO web-pages. The ESO-release is complemented here by AIP-generated catalogues for the four fields at low galactic latitude and published also under the ESO-EIS label.
A complementary survey on the high-latitude EIS-fields with deeper exposure plus further selected high-latitude fields observed in B and R filters was performed by the AIfA (Bonn University, (Schneider, Dietrich) with AIP-participation. The data were used to construct catalogues of galaxy clusters selected via lensing, galaxy overdensity and X-ray emission that were published by Dietrich et al. (2007, A&A 821, 834). The images and catalogues of this survey are released here under the BLOX label.
The fields selected for observations in the three programs are partially overlapping. All single passband images and catalogues of all the sub-programmes are released under the subprogram label, respectively. An attempt was made to identify the most useful images and catalogues for astrophysical research. Those are listed in a comprehensive XMM-WFI imaging table (available also in fits-format).
Object magnitudes published by the ESO-EIS team are given in the AB magnitude system, they were additionally corrected for interstellar extinction. All other catalogues give magnitudes in the Vega-system, not corrected for interstellar extinction. The XMM-WFI imaging table lists per image/catalogue the magnitude system used, describes the magnitude difference between the AB and the Vega system and gives a note if extinction correction was performed.
Many WFI-images have uncertain photometric zeropoints for a number of reasons (variable transparency, no standard star observation during the night). An attempt was made to calibrate the WFI-catalogues using external references. These were the digitized Schmidt plates made available by the SuperCOSMOS Sky Surveys, catalogues based on observations with the optical monitor (OM) onboard XMM-Newton in B and V filters, respectively, and finally the photometric database of the Sloan Digitized Sky Surveys.
Aperture magnitudes of non-extended WFI-sources (SExtractor class_star parameter > 0.95) measured through apertures of three times the average seeing on the stacked images were compared with those of correlated entries in the reference catalogues. A mean magnitude offset and associated standard deviation was determined from a clipped magnitude distribution in an average brightness intervall and listed in the XMM-WFI imaging table. A graphical representation of those correlation results is made available for each filter per field. Catalogues without reliable or with uncertain photometric quality were given a magnitude offset of 99. One might notice different offset magnitudes for a given field between the graphs showing the correlation and the value listed in the table. This mismatch is apparent only and is due to the fact, that the correlation was performed and the graphs produced using sometimes mixed magnitudes (Vega and AB) whereas the tabulated values are always given in the same system.
Below one finds more detailed information/explanation of the columns of the XMM-WFI imaging table.
| Column | Description |
|---|---|
| catalog-name | Name of object catalogue (including field name and filter
designation).
All catalogues were extracted from the corresponding science images using SExtractor (Bertin, E. & Arnouts, S. 1996) |
| image-name | name of corresponding science image (including field name and filter designation) |
| program | Origin of the data, name of the WFI-program which generated and reduced the data and extracted the catalogue |
| magnitude column | Name of the column in the FITS-catalogue containing the
magnitude value used for comparison with the external reference
catalogue. The magnitude column is a program-dependent array of
size nap (number of apertures)
AIP-XMM: nap = 5, aperture diameter = array-index * image-seeing BLOX: nap = 4, apertures of fixed size ranging from 1" to 4" with steps of 1" ESO-EIS (ESO release): nap = 10, apertures of fixed sizes: 1", 1.5", 2", ..., 5", 10" ESO-EIS (AIP release): nap = 5, aperture diameter = array-index * image-seeing |
| mag-system | magnitude system used for the catalogue |
| AB_correction (mag) | Additive term for conversion between AB and Vega systems: mag(AB) = mag(Vega) + AB-correction
Values taken from the Magnitude to Flux Converter (ESO) |
| reddening (mag) | galactic reddening of the field-center calculated with the Galactic Extinction Calulator (NASA/IPAC EXTRAGALACTIC DATABASE) in magnitudes |
| redd. incl. | flag that informs the user whether or not galactic reddening is already applied to the magnitudes of the catalogue |
| reference catalog | External reference for photometric calibration of WFI
data OM: Optical Monitor of XMM-Newton SSS: SuperCOSMOS Sky Surveys SDSS: Sloan Digital Sky Survey |
| delta_mag | Average magnitude difference between reference catalog and
WFI catalogue published here. The difference was calculated as: magdelta = magWFI - magcompare ; where magWFI and magcompare are in the same magnitude system. This offset is not yet applied to the catalogue magnitudes. Therefor one has to substract the delta_mag value from the magnitudes listed in the corresponding catalogue to finally get calibrated magnitudes. SDSS magnitudes in filters ugriz were transformed into ESO's filter-system (B,V,Rc,Ic) using equations given by R. Lupton A magnitude offset =99 indicates unreliable photometry and/or photometric correction |
| delta_mag_error | standard deviation of mean magnitude offset given in previous column |