KsNumber Counts in the Groth and Coppi Fields

We have used William Herschel Telescope/INGRID K s images on two high-latitude fields, the Coppi and Groth strips, to obtain galaxy number counts over $180 arcmin 2 , to a depth of K s $ 21:0. Detection efficiency corrections as a function of object size have been calculated on each pointing. We have used a signalto-noise threshold in two complementary half-exposure images to remove spurious detections. Our data cover the range from K s 14:5 to K s 21:0, so they are useful for investigating a previously reported change in the number count slope (d log N=dm) at K $ 17. We find a slope b 0:54 0:63 for K < 17:5 and a slope f 0:25 0:29 for K > 17:5. A total contribution from galaxies to the extragalactic background light (EBL) in the K band of I 10:5 nW m 2 sr 1 has been calculated. This K-band EBL coming from galaxies accounts for only $50% of the recent measurements of the diffuse EBL. Standard number count models fail to reproduce the observed slope change at K $ 17:5 unless elliptical and spiral formation is pushed to zd2.