total, there are eight surveys covering XXL-N and six surveys covering XXL-S in various filters, as summarised in Table \[TabSurv\] and in Sect. \[SecPhotoSumm\].

Rather than using publicly available catalogues, we performed our own homogeneous photometric extraction per filter and per tile, handling tile overlaps. All magnitudes for all surveys are in the AB system, corrected to 3  aperture magnitudes, and corrected for galactic extinction as described in .

The full photometric catalogues, including the photometric redshift computed as described in , and all sources (not just the counterparts of the X-ray sources) will be published in a forthcoming paper [@Sotiria2018].

The association of published spectroscopic redshifts with our counterparts is described in section \[SecOurSpe\], while more detail about the new AAOmega spectroscopic observations for which we publish the complete catalogue is given in section \[SecLidman\].

  [**North**]{}                                 
  --------------- ------------------ ---------- -------------
  Survey          sub-surveys        mnemonic   filters
  SDSS            –                  sdss       u g r i z
  CFHT            D1 W1 WA WB WC     cfht       u g r i y z
  VISTA           VHS VIDEO VIKING   vista      z Y J H K
  UKIDSS          UDS DXS            ukidss     J H K
  WIRcam          –                  wircam     K
  IRAC            –                  irac       36 45
  GALEX           DIS MIS AIS GI     galex      fuv nuv
  