Millions of galaxies appear in new simulated images from NASA’s Nancy Grace Roman Space Telescope

This simulated Roman deep-field image, containing hundreds of thousands of galaxies, represents only 1.3 percent of the synthetic survey, which itself is only one percent of Roman’s planned survey. The galaxies are color coded – redder ones are further away and whiter ones are closer. The simulation demonstrates Roman’s power to perform large, deep surveys and study the universe statistically in ways not possible with current telescopes. Credit: M. Troxel and Caltech-IPAC/R. Hurt

Scientists have created a giant synthetic study that shows what we can expect from the Nancy Grace Roman Space Telescope’s future observations. Although it represents only a small part of the real future survey, this simulated version contains a staggering number of galaxies – 33 million of them, along with 200,000 foreground stars in our home galaxy.

The simulation will help scientists plan the best observing strategies, test different ways to mine the mission’s vast amounts of data, and explore what we can learn from tandem observations with other telescopes.

“The amount of data Roman will return is unprecedented for a space telescope,” said Michael Troxel, an assistant professor of physics at Duke University in Durham, North Carolina. “Our simulation is a testing ground we can use to make sure we get the most out of the mission’s observations.”

The team obtained data from a mock universe originally developed to support science planning with the Vera C. Rubin Observatory, located in Chile and due to begin full operation in 2024. Because the Roman and Rubin simulations use the same source, the astronomers compare them and see what they can expect to learn from the pair of telescopes’ observations as they both actively scan the universe.

A paper describing the findings, led by Troxel, has been accepted for publication in the The Monthly Notices of the Royal Astronomical Society.

This video begins by showing the most distant galaxies in the simulated deep field image in red. As it zooms out, layers of closer (yellow and white) galaxies are added to the image. By studying different cosmic epochs, Roman will be able to trace the universe’s expansion history, study how galaxies evolved over time, and much more. Credit: Caltech-IPAC/R. Hurt and M. Troxel

Cosmic construction

Roman’s High Latitude Wide Area Survey will consist of both imaging – the focus of the new simulation – and spectroscopy across the same vast swath of the universe. Spectroscopy involves measuring the intensity of light from cosmic objects at different wavelengths, while Roman’s imaging will reveal the precise positions and shapes of hundreds of millions of faint galaxies that will be used to map dark matter. Although this mysterious substance is invisible, astronomers can infer its presence by observing its effects on regular matter.

Anything with mass distorts the fabric of spacetime. The greater the mass, the greater the chain. This creates an effect called gravitational lensing, which occurs when light from a distant source is distorted as it travels past intervening objects. When these lensing objects are massive galaxies or galaxy clusters, background sources can be smeared or appear as multiple images.

Less massive objects can create more subtle effects called weak lensing. Roman will be sensitive enough to use weak lensing to see how clumps of dark matter distort the appearance of distant galaxies. By observing these lensing effects, scientists will be able to fill in more of the gaps in our understanding of dark matter.

This graphic compares the relative sizes of the synthetic image (inset, outlined in orange), the entire area that the astronomers have simulated (the top-center square is outlined in green), and the size of the complete future survey that the astronomers will perform (the large square at the bottom left with blue outline). The background, from the Digitized Sky Survey, illustrates how much sky area each region covers. The synthetic image covers about as much sky as a full moon, and the future Roman survey will cover much more area than the Big Dipper. While it would take the Hubble Space Telescope or the James Webb Space Telescope about a thousand years to image an area as large as the prospective study, Roman will do so in just over seven months. Credit: NASA’s Goddard Space Flight Center and M. Troxel

“Cosmic structure formation theories provide predictions for how seed fluctuations in the early universe grow into the distribution of matter that can be seen through gravitational lensing,” said Chris Hirata, a physics professor at Ohio State University in Columbus, and a co-author of the paper. .

“However, the predictions are statistical in nature, so we test them by observing large areas of the cosmos. With its wide field of view, Roman will be optimized to efficiently survey the sky and complement observatories such as the James Webb Space Telescope, which are designed for deeper study of individual objects.”

Earth and space

The synthetic Roman survey covers 20 square degrees of the sky, roughly equivalent to 95 full moons. The survey itself will be 100 times larger and reveal more than a billion galaxies. Rubin will scan an even larger area — 18,000 square degrees, nearly half the entire sky — but with lower resolution, as it will have to look through Earth’s turbulent atmosphere.

This animation shows the type of science astronomers will be able to do with future Roman deep-field observations. The gravity of intervening galaxy clusters and dark matter can lens the light of more distant objects and distort their appearance as shown in the animation. By studying the distorted light, astronomers can study elusive dark matter, which can only be measured indirectly through its gravitational effects on visible matter. As a bonus, this lens also makes it easier to see the most distant galaxies whose light they magnify. Credit: Caltech-IPAC/R. Hurt

Pairing the Roman and Rubin simulations gives the researchers the first opportunity to try to detect the same objects in both sets of images. This is important because ground-based observations are not always sharp enough to distinguish multiple close sources as separate objects. Sometimes they blur together, affecting weak lens measurements. Now, scientists can determine the difficulties and benefits of “deglazing” such objects in Rubin images by comparing them to Roman ones.

With Roman’s colossal cosmic view, astronomers will be able to achieve far more than the primary goal of the study, which is to study the structure and evolution of the universe, map dark matter and distinguish between the leading theories that try to explain why the expansion of the universe is accelerating. Scientists can comb through the new simulated Roman data to get a taste of the bonus science that will come from seeing so much of the universe in such exquisite detail.

“With Roman’s gigantic field of view, we anticipate many different scientific possibilities, but we will also have to learn to expect the unexpected,” said Julie McEnery, senior project scientist for the Roman mission at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. . “The mission will help answer critical questions in cosmology while potentially revealing entirely new mysteries for us to solve.”

More information:
Michael Troxel et al., A Joint Roman Space Telescope and Rubin Observatory Synthetic Wide-Field Imaging Survey, The Monthly Notices of the Royal Astronomical Society (2023). DOI: 10.1093/mnras/stad664. On arXiv:

Journal information:
Monthly Notices of the Royal Astronomical Society

Leave a Reply

Scroll to Top