An intriguing phenomenon anticipated by Einstein, referred to as gravitational lensing — whereby a nearby galaxy amplifies the appearance of more distant galaxies behind it — is set to become prevalent when NASA’s Nancy Grace Roman Space Telescope begins its scientific operations in 2027 and undertakes expansive surveys of the universe.
Significant lenses are the subject of a recent publication in the Astrophysical Journal, spearheaded by Bryce Wedig, a physics graduate pupil at Washington University in St. Louis, in the Arts & Sciences department.
The investigative team has projected that over 160,000 gravitational lenses, including several hundred appropriate for this analysis, are anticipated to emerge in Roman’s expansive imagery. Each image captured by Roman will be 200 times more significant than infrared images from NASA’s Hubble Space Telescope, and the upcoming abundance of lenses will surpass the hundreds investigated by Hubble so far.
Roman will undertake three primary surveys, offering comprehensive views of the cosmos. The efforts of this scientific team are based on a previous iteration of Roman’s now completely defined High-Latitude Wide-Area Survey. Researchers are composing a follow-up paper to align with the final survey’s specifics, fully supporting the research community.
“The present sample size of these entities from other observatories is relatively modest because we depend on two galaxies to be virtually perfectly aligned along our viewpoint,” Wedig clarified. “Other telescopes face limitations due to a narrower field of vision or less accurate observations, hindering the detection of gravitational lenses.”
Gravitational lenses consist of at least two cosmic entities. In certain instances, a solitary foreground galaxy possesses enough mass to function as a lens, amplifying a galaxy that is nearly directly behind it. Light from the background galaxy bends around the foreground galaxy, creating multiple paths that manifest in observations as distorted arcs and crescents.
Out of the 160,000 lensed galaxies Roman may discover, the team anticipates refining that number down to approximately 500 that are suitable for analyzing the structure of dark matter at smaller scales than those galaxies.
“Roman will not only drastically enhance our sample size — its high-resolution, clear images will also enable us to unearth gravitational lenses that appear smaller in the sky,” stated Tansu Daylan, the principal investigator of the team executing this research program and an assistant professor of physics in Arts & Sciences. Daylan also serves as a faculty fellow at WashU’s McDonnell Center for the Space Sciences. “In the end, both the alignment and brightness of the background galaxies must meet a specific threshold to characterize the dark matter within the foreground galaxies.”
Through Roman, the team aims to gather data about the size and structures of early galaxies. “Detecting gravitational lenses and identifying clusters of dark matter within them is a matter of slim probabilities. With Roman, we can cast a broad net and often expect favorable outcomes,” Wedig remarked. “Dark matter will remain unseen in the images — it’s invisible — but we can assess its effects.”
“Ultimately, the question we’re attempting to resolve is: What particle or particles comprise dark matter?” Daylan added. “While certain properties of dark matter are acknowledged, we essentially have no understanding of what constitutes it. Roman will aid us in discerning how dark matter is distributed on small scales, thereby revealing its particle nature.”
Prior to Roman’s launch, the team will also seek more candidates utilizing observations from the European Space Agency’s Euclid mission and the forthcoming ground-based Vera C. Rubin Observatory in Chile, which will commence full-scale operations shortly.
“Once Roman’s images are available, the researchers will integrate them with complementary visible light images from Euclid, Rubin, and Hubble to optimize their understanding of these galaxies,” noted Simon Birrer, an assistant professor at Stony Brook University and a co-investigator of the research project.
“We will stretch the boundaries of our observations and utilize every gravitational lens detected by Roman to clarify the particle nature of dark matter,” Daylan remarked.
Read more on the Space Telescope Science Institute website.
The Nancy Grace Roman Space Telescope is operated at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, with contributions from NASA’s Jet Propulsion Laboratory in southern California; Caltech/IPAC in Pasadena, California; the Space Telescope Science Institute in Baltimore; and a scientific team composed of researchers from various institutions. The main industrial collaborators include BAE Systems, Inc. in Boulder, Colorado; L3Harris Technologies in Melbourne, Florida; and Teledyne Scientific & Imaging in Thousand Oaks, California.
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