We present a K survey of 29 fields covering approximately 90 arcmin ^ { 2 } from the Medium Deep Survey ( MDS ) catalogue down to a completeness magnitude of K = 18.0 ( limiting magnitude K = 19.0 ) .
The morphology obtained by the MDS team using high resolution images from HST/WFPC2 along with our NIR observations allow a Colour–Magnitude and Colour–Colour analysis that agrees in general with spectral evolution models [ Bruzual & Charlot 1998 ] especially if a reasonable range of metallicities for the Simple Stellar Populations used ( 0.2 < Z / Z _ { \odot } < 2.5 ) is considered .
However , a significant population of spheroids was found , which appear bluer than expected , confirming previous observations ( Forbes et al .
1996 , Koo et al .
1996 , Glazebrook et al .
1998 ) .
This blueness might possibly signal the existence of non-negligible star formation in ellipticals and bulges at medium redshift .
A number counts calculation for different morphological types show disks become the dominant population at faint magnitudes .
The median redshift of the sample is z \sim 0.2 , from a photometric redshift estimation using V - K and I - K .
A search for EROs in the survey field was also performed , with no detection of objects having I - K > 4.5 , setting an upper limit to the number density of EROs at dn _ { EROs } / d \Omega < 0.011 arcmin ^ { -2 } ( K \leq 18.0 ) .