We present new results on the cosmological evolution of the near-infrared galaxy luminosity function , derived from the analysis of a new sample of \sim 22 , 000 K _ { AB } \leq 22.5 galaxies selected over an area of 0.6 square degrees from the Early Data Release of the UKIDSS Ultra Deep Survey ( UDS ) .
Our study has exploited the multi-wavelength coverage of the UDS field provided by the new UKIDSS WFCAM K and J -band imaging , the Subaru/XMM-Newton Deep Survey and the Spitzer -SWIRE Survey .
The unique combination of large area and depth provided by this new survey minimises the complicating effect of cosmic variance and has allowed us , for the first time , to trace the evolution of the brightest sources out to z \simeq 2 with good statistical accuracy .

In agreement with previous studies we find that the characteristic luminosity of the near-infrared luminosity function brightens by \simeq 1 magnitude between z = 0 and z \simeq 2 , while the total density decreases by a factor \simeq 2 .
Using the rest-frame ( U - B ) colour to split the sample into red and blue galaxies , we confirm the classic luminosity-dependent colour bimodality at z \raisebox { -3.698858 pt } { ~ { } \shortstack { $ < $ \ [ -0.07 cm ] $ \sim$ } } ~ { } 1 .
However , the strength of the colour bimodality is found to be a decreasing function of redshift , and seems to disappear by z \mathrel { \hbox to 0.0 pt { \lower 3.0 pt \hbox { $ \sim$ } } \raise 2.0 pt \hbox { $ > $ } } 1.5 .
Due to the large size of our sample we are able to investigate the differing cosmological evolution of the red and blue galaxy populations .
It is found that the space density of the brightest red galaxies ( M _ { K } \leq - 23 ) stays approximately constant with redshift , and that these sources dominate the bright-end of the luminosity function at redshifts z \raisebox { -3.698858 pt } { ~ { } \shortstack { $ < $ \ [ -0.07 cm ] $ \sim$ } } ~ { } 1 .
In contrast , the brightening of the characteristic luminosity and mild decrease in space density displayed by the blue galaxy population leads them to dominate the bright-end of the luminosity function at redshifts z \raisebox { -3.698858 pt } { ~ { } \shortstack { $ > $ \ [ -0.07 cm ] $ \sim$ } } ~ { } 1 .