the first galaxies

z~7.0 Drop-Out Galaxies

This panel shows four candidate galaxies that are likely to have redshifts of 7 and thus have emitted their light whe n the universe was just 750 million years old. Each of the four candidate high-redshift galaxies are presented in a distinct row. All four candidate galaxies are shown using images at each of five different wavelengths (591 nm, 776 nm, 944 nm, 1119, and 1604 nm). These galaxies are all clearly detected at wavelengths redder than 1000 nm, but remain completely undetected at wavelengths bluer than 800 nm. This abrupt drop-off in the flux is strongly characteristic of star-forming galaxies at high redshifts and occurs due to the absorption of light by the large amounts of neutral hydrogen in the universe at early times. Astronomers use the presence of this break to find high-redshift galaxies. The present sources were found over the Hubble Ultra Deep Field and the Great Observatory Origins Deep Survey Fields. The search is described in a recently accepted paper to Nature.

Credit:Rychard Bouwens

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