A team of astrophysicists has created a simulated image that shows how the Nancy Grace Roman Space Telescope could conduct a mega-exposure similar to but far larger than Hubble’s celebrated Ultra Deep Field Image.
This Hubble observation transformed our view of the early universe, revealing galaxies that formed just a few hundred million years after the big bang.

“Roman has the unique ability to image very large areas of the sky, which allows us to see the environments around galaxies in the early universe,” said Nicole Drakos, a postdoctoral scholar at the University of California Santa Cruz, who led the study. “Our study helps demonstrate what a Roman ultra-deep field could tell us about the universe, while providing a tool for the scientific community to extract the most value from such a program.”

By capturing the Hubble Ultra Deep Field image, astronomers pulled aside the cosmic curtains to reveal that a tiny, seemingly empty slice of the sky was actually teeming with thousands of galaxies, each containing billions of stars. The Hubble team harnessed the power of a long exposure time – hundreds of hours between 2002 and 2012 – which allowed the telescope to collect more light than it could in a single, short observation. The resulting image helped us see more than 13 billion years back in time.

Hubble’s Ultra Deep Field offers an incredible window to the early universe, but an extremely narrow one, covering less than one ten millionth of the whole sky. The new simulation showcases Roman’s power to perform a similar observation on a much larger scale, revealing millions of galaxies instead of thousands. While a Roman ultra-deep field would be just as sharp as Hubble’s and peer equally far back in time, it could reveal an area 300 times larger, offering a much broader view of cosmic ecosystems.

“The Hubble Ultra Deep Field gave us a glimpse of the universe’s youth, but it was too small to reveal much information about what the cosmos was really like back then as a whole,” said Brant Robertson, an astronomy professor at the University of California Santa Cruz and a co-author of the study. “It’s like looking at a single piece of a 10,000-piece puzzle. Roman could give us 100 connected puzzle pieces, offering a much better picture of what the early universe was like and opening up new scientific opportunities.”

To generate their simulated Roman ultra-deep field image, Drakos and co-authors created a synthetic catalog of galaxies, complete with detailed information about each one. By doing so, the team essentially created a mock universe, basing their synthetic galaxies on dark matter simulations and observation-based models. They made the galaxy catalog publicly available so other scientists can use it to prepare for future Roman observations. The team also created an interactive website where users can zoom and pan across the full-resolution image.

The team’s results will be published in The Astrophysical Journal.

Looking far and wide

Astronomers usually have to choose between taking a shallow, wide-area image and capturing a very sensitive, deep image since telescope time is a precious commodity. But with Roman’s enormous field of view and infrared vision, they will be able to peer far and wide simultaneously, opening up new avenues of cosmic exploration.

This video demonstrates how Roman could expand on Hubble’s iconic Ultra Deep Field image. While a similar Roman observation would be just as sharp as Hubble’s and see equally far back in time, it could reveal an area 300 times larger, offering a much broader view of cosmic ecosystems.
Credits: NASA’s Goddard Space Flight Center