tokens: GI surveys mainly focus on the XMM-LSS area. The XXL-S field is fully covered by GALEX GR6/7 with AIS, Medium Imaging Survey (MIS), and/or GI programs. VISTA Three public European Southern Observatory (ESO) large programme surveys have observed the XXL field in the near infrared (, , , , filters: ) with the Visible and Infrared Survey Telescope for Astronomy 6 (VISTA) in various depths. XXL-N is covered by all three surveys: VISTA Hemisphere Survey (VHS, PI: R., McMahon), VISTA Kilo-degree Infrared Galaxy Survey(VIKING, PI: W. Sutherland), and VISTA Deep Extragalactic Observations Survey (VIDEO, PI: M. Jarvis), while the XXL-S is covered only by the VHS survey. IRAC Both XXL fields have been targeted with the Infrared Array Camera (IRAC) on board the Spitzer Space Telescope 7 providing imaging at and over the whole area (XXL-N; PI: M. Bremer, XXL-S; SPT- Spitzer Deep Field, SSDF, Ashby et al. 2014 ). WISE The Wide-field Infrared Survey Explorer 8 (WISE) is an all-sky mission observing the sky from to . In this work we use the ALLWISE data release 9 , which provides imaging for the whole XXL field in all four WISE filters. 3.2. XXL-N Observations covering exclusively the XXL-N area: CFHT The Canada-France-HawaiiTelescope 10 (CFHT) hasobserved the parts of the XXL-N area as part of the CHFT-LegacySurvey 11 (CFHTLS) in two configurations a) wide area ( W1 field) and b)deep field (D1 field) observed with MEGACam, providingimaging in the filters: , , , , (). In this work we use the T0007 data release downloaded from Terapix 12 . We complemented the coverage of CFHT with three additional fields to the north of W1 . The WA and WB fields were observed in the , , filters while the WC field was observed in the filter (PI: M. Pierre). Additionally, XXL-N has been observed with the WIRcam camera on CFHT in the band (, VIPERS-Multi-Lambda Survey). Details on the observations and data reduction are provided in Moutard et al. (2016a , b) . SDSS The Sloan Digital Sky Survey 13 (SDSS) provides observations in the whole XXL-N area in the filters: , , , , (). In this work we use the DR10 data release ( Ahn et al. 2014 ). UKIDSS The UKIRT Infrared Deep Sky Survey 14 (UKIDSS, Dye et al. 2006 ) has two fields overlapping with XXL-N: the Ultra Deep Survey (UDS), and the Deep Extragalactic Survey (DXS) targeting the XMM-LSS area in , , and , bands, respectively. Here we use the DR10 data release downloaded from the WFCAM Science Archive 15 . 3.3. XXL-S Observations covering exclusively the XXL-S area: BCS The Blanco Cosmology Survey 16 (BCS; Desaiet al. 2012 ) has targeted an area of which overlaps with the XXL-S field using the MOSAIC II imager at the Cerro Tololo Inter-American Observatory 17 (CTIO). The observations cover the , , , bands (). The images used in this work were analysed as described in Menanteau et al. (2009) . DECam The Dark Energy Camera 18 (DECam) is the successor of the MOSAIC II camera at CTIO. We observed the XXL-S field (PI: C. Lidman) in
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