The album, which my colleagues and I compiled, allows us to track the family tree of galaxies over more than 90% of the age of the universe.
We used the 6.5-metre Magellan Baade Telescope and FourStar infrared camera to snap these images over 45 nights.
Taking inspiration from the camera, we named the study the FourStar Galaxy Evolution Survey, or ZFOURGE for short.
To do this, we need to account for galaxies moving away from us and observe how much their light is shifted to longer (redder) wavelengths. The greater the shift, the farther away a galaxy is from us.
Unfortunately, determining this shift often requires time-consuming observations with spectroscopic instruments. The advantage of ZFOURGE is its unique filter set, which overcomes this challenge and allows us to probe numerous galaxies at once, while also measuring accurate distances.
Such information allowed us to classify these galaxies according to their physical properties and thus construct a “family tree” to better investigate how they evolve through cosmic time.
It is commonly believed that these small galaxies grew by way of hierarchical formation, a process in which they merged with their neighbours to form larger galaxies like our Milky Way.
Mature-aged baby boomers
ZFOURGE has produced a wealth of information, resulting in numerous scientific publications that continue to expand our understanding of galaxies and how they evolve.
One of the most exciting discoveries was the finding that the first galaxies, formed in the early universe, might have matured much sooner than expected.
Such findings pose new questions for astronomers and allow us to build on existing models of galaxy formation and evolution.
The Milky Way’s family album
Another exciting discovery came about by observing galaxies that resemble the ancestors of the Milky Way. It was discovered that 10 billion years ago, the Milky Way was potentially churning out newborn stars 30 times faster than the present.
By examining these progenitor galaxies, we found that the Milky Way potentially began life as a small clump of stars, before building itself up into the grand spiral galaxy we know it as today.
Hunting for black holes
By combining the data from ZFOURGE with images from numerous other ground and space-based telescopes, we then set out in search of supermassive black holes.
While you may think this is a futile expedition, given black holes are “black”, those that are actively feeding on surrounding gas and dust are known to be among the brightest objects in the universe.
Such black holes have long been believed to be detrimental to a galaxy’s health, as they either heat the cold gas and dust required for birthing new stars, or simply blast it away with their immense amount of energy.
While our survey is now complete and our catalogue of galaxies has been made public, this is only the beginning for the ZFOURGE survey.
With a family tree of more than 70,000 galaxies, spanning most of cosmic time, there’s plenty of data for astronomers around the world to dive into and make their own exciting discoveries.