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

Understand

The observed number counts of high-redshift galaxy candidates have been used to build up a statistical description of star-forming activity at redshift z >~ 7, when galaxies reionized the Universe.

• Standard models predict that a high incidence of gravitational lensing will probably distort measurements of flux and number of these earliest galaxies.
• The raw probability of this happening has been estimated to be ~ 0.5 percent, but can be larger owing to observational biases.
• Here we report that gravitational lensing is likely to dominate the observed properties of galaxies with redshifts of z >~ 12, when the instrumental limiting magnitude is expected to be brighter than the characteristic magnitude of the galaxy sample.