The Nancy Grace Roman Space Telescope, NASA's next flagship astrophysics mission after the James Webb Space Telescope, recently selected its science teams, and a UArizona research group has been selected for two of those teams. A total of 91 proposals were received in response to the opportunity, and the proposals from UArizona are among the 30 selected for funding.

The Roman Space Telescope, scheduled to launch by May 2027, will function as the wide-eyed cousin of the Hubble Space Telescope. Each image of Roman will have the same resolution as Hubble but cover an area of the sky that is 100 times larger. This will allow scientists to build an incredibly detailed map of the universe, which will help answer questions about cosmic mysteries in the areas of dark energy, exoplanets and infrared astrophysics.

NASA's call for Roman science teams was made across different categories, and the research group at the Arizona Cosmology Lab was selected for two teams – one in the wide-field science category and one in project infrastructure. Elisabeth Krause, associate professor of astronomy and physics at UArizona, leads the wide-field science team "Kinematic Lensing With the Roman Space Telescope," and the research group is planning to take a new approach to look at the data captured by Roman.

The project infrastructure team “Maximizing Cosmological Science With the Roman High Latitude Imaging Survey" is a multi-institutional effort. While the wide-field science team was funded to develop a novel, high-risk/high-reward idea, the project infrastructure team will focus on established measurement techniques that will reach a new level of precision given Roman’s exquisite instruments. Within this larger team, Tim Eifler, associate professor of astronomy at UArizona, is leading the working group that will extract the cosmological information.

"We and our team at the Arizona Cosmology Lab are all very excited to be working on this over the coming five years," Krause said.

For the wide-field science project, the group was funded to implement a new type of cosmological measurement called kinematic lensing.

Image

Kinematic lensing is an improved version of the long-established weak-lensing technique. Weak lensing is based on an idea that galaxies appear slightly distorted compared to their original shape, emitting light that gets constantly deflected in the gravitational fields of massive objects in the universe. This idea dates back to Albert Einstein, who discovered that light does not travel as a straight line, but rather follows the shortest path in a curved space, a phenomenon that is applicable to all the light particles or photons in the universe.

Everything in the universe is lensed, some objects more and some less, Eifler said. By measuring the lensing effect, we can study how matter structures in the universe have evolved over time.   

Roman has two types of observations. In addition to the images, it will also measure spectra for lots of galaxies. Kinematic lensing smartly combines these two Roman datasets into a new cosmological measurement, Krause said. This results in a much larger amount of cosmological information and allows us to study dark matter and dark energy at higher accuracy.

"Our graduate students ran lots of simulated analyses and showed that this idea works under realistic conditions," Krause added.

"The fact that NASA believes in us is very reassuring and motivating," said Pranjal Rajendra Singh, one of the graduate students who helped write the proposal for the wide-field science project. Jiachuan Xu and Yu-Hsiu Huang are the other graduate students involved in the kinematic lensing team.

The team also includes Eric Huff, a staff scientist at the NASA Jet Propulsion Laboratory. Huff, Krause and Eifler were the first authors of the original paper that outlines the theoretical basis of the kinematic lensing idea.

"It's really nice to see that something we wrote up when we were junior postdocs and grad students ourselves may now actually happen with the next NASA flagship mission," Huff said.

As part of the multi-institutional project infrastructure group, the UArizona researchers are developing the complex science software that can interpret the measurements for NASA and the broader Roman community.

"Kinematic lensing is a new technique we are developing, but there are a lot of established cosmological measurements that Roman will take that need to be modeled and interpreted," Eifler said.

For this, the Arizona Cosmology Lab has built a dedicated software pipeline that was used on the recently completed ground-based Dark Energy Survey. In close collaborations with the other institutions from the project infrastructure team, this science interpretation software will now be upgraded and adapted for Roman. 

The Arizona Cosmology Lab has a world-class cosmology group where the researchers build algorithms to analyze large datasets from ongoing and future space missions. The lab was started in 2018, and one of its core science goals is to explore the exact physics behind dark energy and dark matter. 

Along with Roman, the Vera Rubin Observatory, which will start observing in 2025, will keep the Arizona Cosmology Lab busy in the coming years, Krause said. Data from the observatory will deliver information from billions of galaxies across the sky. The lab is also involved in the NASA SPHEREx mission, which will help understand the very early phase of the universe.

"The next 10 years will be just a really amazing adventure for astronomers and physicists like us who want to interpret cosmology data," Eifler said. "There's so many fantastic instruments coming, and the Roman Space Telescope is one of them."