English: A team of astronomers has used ALMA (the Atacama Large Millimeter/submillimeter Array) to pinpoint the locations of over 100 of the most fertile star-forming galaxies in the early Universe.

The best map so far of these distant dusty galaxies was made using the Atacama Pathfinder Experiment (APEX), but the observations were not sharp enough to unambiguously identify these galaxies in images at other wavelengths. ALMA needed just two minutes per galaxy to pinpoint each one within a comparatively tiny region 200 times smaller than the broad APEX blobs, and with three times the sensitivity.

This image shows six of the galaxies as seen in the sharp new observations by ALMA (in red). The big red circles indicate the regions where galaxies had been detected by APEX. The earlier telescope did not have sharp enough images to pin down the identity of the galaxies, many candidates appear in each circle. The ALMA observations, at submillimetre wavelengths, are overlaid on an infrared view of the region as seen by the IRAC camera on the Spitzer Space Telescope (coloured blue).