The Gas Supplies of the First Galaxies

In 2016 the Atacama Large Millimeter/submillimeter Array (ALMA) imaged galaxies at the very limits of the observable universe

Credit: ALMA (ESO/NAOJ/NRAO)/NASA/ESA/J. Dunlop et al. and S. Beckwith (STScI) and the HUDF Team — This image combines a background picture taken by the NASA/ESA Hubble Space Telescope (blue/green) with a very deep ALMA view of this field (orange, marked with circles). All the objects seen by ALMA appear to be massive star-forming galaxies

As we have already noticed in another post, looking far into space also means looking back in time due to the finite speed of light.

Exploiting this bond between time and distance, astronomers have derived the general lines of the Universe’s evolutionary history by putting together sky observations showing objects at different distances. In fact, galaxies in the Local Universe look very different from galaxies billions of light-years away from us.

The analysis of how galaxies change based on their distance in space and time suggests that the further we look back in time, the higher the star formation rate. Starting from the time when the first galaxies began to appear, around 13 billion years ago, the ability to form new stars grew to reach its peak around ten billion years ago. After that, it relentlessly declined. Consequently, the galaxies in the Local Universe, now many billions of years old, form very few stars compared to the young galaxies that populated the early universe.

What fueled the ability of those ancient galaxies to form new stars at breakneck rates? The only telescope capable of…