The new study, published in the Astrophysical Journal, predicts that Roman's wide-field infrared surveys will dramatically expand the known lens population, offering hundreds of ideal candidates for dark matter investigations. Each Roman image will cover 200 times the sky area of similar Hubble images, enabling discovery of many small-scale lenses that previous telescopes missed due to limited precision and field of view.
"Other telescopes are either limited to a smaller field of view or less precise observations, making gravitational lenses harder to detect," said Wedig. "The current sample size of these objects from other telescopes is fairly small because we're relying on two galaxies to be lined up nearly perfectly along our line of sight."
Gravitational lenses typically involve a foreground galaxy with enough mass to bend light from a background galaxy into arcs or crescents, allowing scientists to study invisible structures like dark matter. Of the tens of thousands expected, only about 500 are likely to provide the right conditions to examine dark matter distribution on small scales.
Tansu Daylan, assistant professor of physics at Washington University and principal investigator of the project, noted, "Roman will not only significantly increase our sample size - its sharp, high-resolution images will also allow us to discover gravitational lenses that appear smaller on the sky."
The team plans to refine their findings using visible-light images from the European Space Agency's Euclid mission, NASA's Hubble Space Telescope, and the upcoming Vera C. Rubin Observatory in Chile. "We will push the limits of what we can observe, and use every gravitational lens we detect with Roman to pin down the particle nature of dark matter," Daylan said.
"Ultimately, the question we're trying to address is: What particle or particles constitute dark matter?" Daylan added. "Roman will help us to distinguish how dark matter is distributed on small scales and, hence, its particle nature."
Wedig emphasized the scale of the project: "With Roman, we can cast a wide net and expect to get lucky often. We won't see dark matter in the images - it's invisible - but we can measure its effects."
Research Report:The Roman View of Strong Gravitational Lenses
Related Links
Washington University in St. Louis
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