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In this side view of the simulated universe, each dot represents a galaxy whose size and luminosity correspond to its mass. Discs from different eras illustrate how Roman will be able to see the universe across cosmic history. Astronomers will use such observations to piece together how cosmic evolution led to the web-like structure we see today. Credit: NASA’s Goddard Space Flight Center and A. Yung
A new simulation shows how[{” attribute=””>NASA’s Nancy Grace
Combining Roman’s large view with Hubble’s broader wavelength coverage and Webb’s more detailed observations will offer a more comprehensive view of the universe.
In this simulated view of the deep cosmos, each dot represents a galaxy. The three small squares show Hubble’s field of view, each revealing a different region of the synthetic universe. Roman will quickly be able to map an area as large as the entire zoomed-out image, which will give us a glimpse of the universe’s largest structures. Credit: NASA’s Goddard Space Flight Center and A. Yung
The simulation covers a two-square-degree section of the sky, which is roughly 10 times the apparent size of a full moon, and contains over 5 million galaxies. It is based on a well-tested galaxy formation model that represents our current understanding of how the universe works. Using an extremely efficient technique, the team can simulate tens of millions of galaxies in less than a day – something that could take years with conventional methods. Once Roman launches and starts delivering real data, researchers can compare it to a series of such simulations, putting their models to the ultimate test. It will help unravel the physics of galaxy formation, dark matter – a mysterious substance only observed through the effects of gravity – and much more.
An article describing the results was published in Monthly Notices of the Royal Astronomical Society in December 2022.
To unravel the cosmic web
Galaxies and galaxy clusters glow in clumps along invisible strands of dark matter in a tapestry the size of the observable universe. With a broad enough overview of that tapestry, we can see that the large-scale structure of the universe is web-like, with threads stretching across hundreds of millions of light years. Galaxies are found primarily at the intersections of the filaments, with large “cosmic voids” between all the shining filaments.
This is what the cosmos looks like now. But if we could rewind the universe, we would see something completely different.
This image, containing millions of simulated galaxies strewn across space and time, shows the regions Hubble (white) and Roman (yellow) can capture in a single snapshot. It would take Hubble about 85 years to map the entire region shown in the image at the same depth, but Roman could do it in just 63 days. Roman’s larger views and rapid survey speeds will reveal the evolving universe in ways never before possible. Credit: NASA’s Goddard Space Flight Center and A. Yung
Instead of giant, blazing stars scattered about in galaxies each separated by even greater distances, we would find ourselves immersed in a sea of[{” attribute=””>plasma (charged particles). This primordial soup was almost completely uniform, but thankfully for us, there were tiny knots. Since those clumps were slightly denser than their surroundings, they had slightly larger gravitational pull.
Over hundreds of millions of years, the clumps drew in more and more material. They grew large enough to form stars, which were gravitationally drawn toward the dark matter that forms the invisible backbone of the universe. Galaxies were born and continued to evolve, and eventually, planetary systems like our own emerged.
In this side view of the simulated universe, each dot represents a galaxy whose size and luminosity correspond to its mass. Discs from different eras illustrate how Roman will be able to see the universe across cosmic history. Astronomers will use such observations to piece together how cosmic evolution led to the web-like structure we see today. Credit: NASA’s Goddard Space Flight Center and A. Yung
Roman’s panoramic view will help us see what the universe was like at different stages and fill in many gaps in our understanding. For example, while astronomers have detected “halos” of dark matter enveloping galaxies, they are not sure how they formed. By seeing how gravitational lensing caused by dark matter distorts the appearance of more distant objects, Roman will help us see how haloes evolved over cosmic time.
“Simulations such as these will be crucial in linking unprecedented large-scale galaxy surveys from Roman to the invisible scaffolding of dark matter that determines the distribution of these galaxies,” said Sangeeta Malhotra, an astrophysicist at Goddard and co-author of the paper.
To see the bigger picture
Studying such huge cosmic structures with other space telescopes is not practical because it would take hundreds of years of observations to stitch together enough images to see them.
“Roman will have the unique ability to match the depth of the Hubble Ultra Deep Field, yet cover several times more sky area than broad surveys such as the CANDELS survey,” Yung said. “Such a full view of the early universe will help us understand how representative the Hubble and Webb snapshots are of what it was like then.”
Roman’s wide view will also act as a road map Hubble and Webb can use to zoom in on areas of interest.
The Roman Space Telescope is a NASA observatory designed to uncover the secrets of dark energy and dark matter, search for and image exoplanets, and explore many topics in infrared astrophysics. Credit: NASA
Roman’s extensive sky surveys will be able to map the universe up to a thousand times faster than Hubble. It will be possible because of the observatory’s rigid structure, fast swing speed and the telescope’s large field of view. Roman will move quickly from one cosmic goal to the next. Once a new target is acquired, the vibrations will subside quickly because potentially wobbly structures such as the solar panels are fixed in place.
“Roman will take about 100,000 images each year,” said Jeffrey Kruk, a research astrophysicist at Goddard. “Given Roman’s larger field of view, it would take longer than our lifetime even for powerful telescopes like Hubble or Webb to cover as much sky.”
By providing a giant, stark view of cosmic ecosystems and teaming up with observatories like Hubble and Webb, Roman will help us solve some of the most profound mysteries in astrophysics.
Reference: “Semi-analytic forecasts for Roman – the dawn of a new era of deep-wide galaxy surveys” by LY Aaron Yung, Rachel S Somerville, Steven L Finkelstein, Peter Behroozi, Romeel Davé, Henry C Ferguson, Jonathan P Gardner, Gergö Popping , Sangeeta Malhotra, Casey Papovich, James E Rhoads, Micaela B Bagley, Michaela Hirschmann, and Anton M Koekemoer, December 8, 202, Monthly Notices of the Royal Astronomical Society.
DOI: 10.1093/mnras/stac3595
At NASA’s Goddard Space Flight Center, the Nancy Grace Roman Space Telescope is monitored with collaboration from NASA’s Jet Propulsion Laboratory and Caltech/IPAC in Southern California, as well as the Space Telescope Science Institute in Baltimore. A diverse team of researchers from various research institutions forms the core of the project’s scientific team. The project is supported by key industrial partners, including Ball Aerospace and Technologies Corporation based in Boulder, Colorado, L3Harris Technologies in Melbourne, Florida, and Teledyne Scientific & Imaging in Thousand Oaks, California.
