We analyse recently acquired near-infrared Hubble Space Telescope imaging of the GOODS-South field to search for star forming galaxies at z \approx 7.0 .
By comparing WFC 3 0.98 \mu m Y -band images with ACS z -band ( 0.85 \mu m ) images , we identify objects with colours consistent with Lyman break galaxies at z \simeq 6.4-7.4 .
This new data covers an area five times larger than that previously reported in the WFC3 imaging of the Hubble Ultra Deep Field , and affords a valuable constraint on the bright end of the luminosity function .
Using additional imaging of the region in the ACS B , V and i -bands from GOODS v2.0 and the WFC3 J -band we attempt to remove any low-redshift interlopers .
Our selection criteria yields 6 candidates brighter than Y _ { AB } = 27.0 , of which all except one are detected in the ACS z -band imaging and are thus unlikely to be transients .
Assuming all 6 candidates are at z \approx 7 this implies a surface density of objects brighter than Y _ { AB } = 27.0 of 0.30 \pm 0.12 arcmin ^ { -2 } , a value significantly smaller than the prediction from z \approx 6 luminosity function .
This suggests continued evolution of the bright end of the luminosity function between z = 6 \to 7 , with number densities lower at higher redshift .