One of the most amazing things about current astronomy is how researchers are finding ways to tease out answers to questions all of us expected to see the JWST solving. As that telescope is now more than ten years late to launch, at a certain level, people just got tired of waiting. Also, we still have Hubble, and we now have the ground-based millimeter and sub-millimeter telescope ALMA.  Working together, these systems can identify high mass galaxy clusters that can gravitationally magnify more distant galaxies. While this gravitational lensing acts more like a distorting funhouse mirror than a perfectly formed lens, the systems, however distorted, are still magnified, and this allows us to see things otherwise too far away in this pre-JWST era, and sometimes it even lets us see things we didn’t expect to even see with JWST! 

In a new study appearing in Nature and led by Katherine Whitaker, researchers look at massive distant galaxies whose light has been gravitationally lensed. Six of these systems appear to have already exhausted all of their star-forming material when the universe was just three billion years old. This was not expected, and now the question becomes, “How?”

One of the startling revelations of the past decade has been that galaxies form in different ways. Early on in the universe, massive galaxies could form through the collapse of massive clouds of material. Small and medium-sized galaxies could also form this way, and since the beginning, there have been galaxies of all sizes. Over the past ten billion years or so, smaller galaxies have merged together to form bigger and bigger systems, and massive systems have periodically eaten smaller systems and gained a bit of girth in the process.

In trying to understand how the massive systems used ran out of star-forming material so fast, researchers are considering different options. According to Whitaker, we need to ask: Did a supermassive black hole in the galaxy’s center turn on and heat up all the gas? If so, the gas could still be there, but now it’s hot. Or it could have been expelled and now it’s being prevented from accreting back onto the galaxy. Or did the galaxy just use it all up, and the supply is cut off? These are some of the open questions that we’ll continue to explore with new observations down the road.

In theory, when and if JWST is successfully put into action, it will be able to directly observe these kinds of systems without relying on the image distorting effects of gravitational lensing. In theory, the wait is almost over, and the telescope should finally be launching later this year. Of course, they said that back in 2018, and then, it didn’t launch. So here is to hoping but not counting our telescopes before they launch.

More Information

Hubble press release

NASA Goddard press release

NRAO press release

University of Massachusetts Amherst press release

“Quenching of star formation from a lack of inflowing gas to galaxies,” Katherine E. Whitaker et al., 2021 September 22, Nature