A distortion of very-high-redshift galaxy number counts by gravitational lensing

The observed number counts of high-redshift galaxy candidates have been used to build up a statistical description of star-forming activity at redshift of about z>7. Here it is reported that gravitational lensing is likely to dominate the observed properties of galaxies with redshifts of about z>12, when the instrumental limiting magnitude is expected to be brighter than the characteristic magnitude of the galaxy sample. The number counts could be modified by an order of magnitude. Future surveys will need to be designed to account for a significant gravitational lensing bias in high-redshift galaxy samples.