Dark matter, a substance in the universe that does not emit, absorb, or reflect light, cannot be directly detected using conventional telescopes or other imaging techniques. And so astrophysicists have tried to identify alternative methods for detecting dark matter for decades.
Researchers at Tsinghua University, the Purple Mountain Observatory, and Peking University recently conducted a study to explore the possibility of directly detecting dark photons, prominent dark matter candidates, using radio telescopes. Their paper has been published in Physical review lettersIt could benefit future searches for dark photons, hypothetical particles that can carry a force in dark matter, similar to the way electromagnetic photons are carried in ordinary matter.
“Our previous work studied the conversion of dark photons into photons in the solar corona,” Haiping An, one of the researchers who conducted the study, told Phys.org.
“This process involves the excitation of free electrons by photon dark fields, resulting in the emission of normal photons. Based on this work, Jia and I thought of using free electrons in a concave telescope to induce electromagnetic signals and then using a fast telescope to search for such a signal.”
Soon after, they began to explore the use of concave telescopes to search for electromagnetic signals related to the dark photon, and Ahn and his colleagues realized that due to the non-relativistic nature of dark matter, the reflector in such telescopes must be spherical and the signal receiver must be placed in the center of this sphere.
However, existing radio telescopes, such as the Five Hundred Meter Aperture Spherical Radio Telescope (FAST) in China, are designed to observe distant radio signals, so their dish shape is parabolic, with the receiver positioned at a focal point.
This means that the electromagnetic signals created by the dark photons will not be concentrated in their receiver.
“After this realization, we temporarily abandoned this idea,” Ann explained. In the summer of 2021, I was invited to give lectures on dark matter at the UFITS Summer School for Cosmology held at the FAST site, where I studied the details of how the FAST telescope works. I learned that a receiver suspended above the dish could move so that the telescope could detect radio waves from Different directions.Then I came up with the idea that although the electromagnetic waves caused by the photon dark matter do not focus on the receiver, the electromagnetic field can form a dish top distribution, and this distribution can be accurately calculated theoretically.”
According to An’s later theoretical predictions, the moving receiver in radio telescopes should be able to collect electromagnetic signals at different locations. The signals collected by the receiver can then be compared to the distributions predicted by theory, which should help improve the telescopes’ sensitivity to photon-induced dark signals.
“With our colleagues, we then set about calculating this signal,” Ann said. “To our surprise, we found that even without considering the distribution, with the extraordinary sensitivity, even with the fact that the signal caused by the dark photon’s dark matter is not focused on the receiver, the sensitivity of the FAST telescope has already exceeded the limitations of the CMB, which means that the FAST telescope can detect matter.” dark matter if the dark matter is made up of the dark photon and is in the right mass region.”
To further assess the feasibility of their proposed method for searching for dark photons, An and colleagues also analyzed observational data collected by the FAST radio telescope, located in a village in the mountains in the Guizhou region of China. This data was provided by Professor Xiaoyuan Huang, who is also a co-author of the latest paper.
“We analyzed the data and put the most stringent constraints on the model in the 1-1.5GHz frequency range,” he said. “We realized that photon dark matter can induce electrical signals on dipole antennas and that, given the non-relativistic nature, we can use interferometry technology to improve sensitivity. Therefore, we calculated the potential sensitivity of the LOFAR telescope and SKA receiver and found that both have the potential to detect photon dark matter.” dark.”
Overall, the analyzes by the team of researchers indicate that radio telescopes can enable direct detection of dark photons. Their work can thus broaden horizons in the ongoing search for dark photons, especially ultralight dark photons.
“In the early 1960s, while doing research in radio astronomy, Penzias and Wilson stumbled upon an unexpected low-level background noise,” said Ann. This noise was later confirmed to be cosmic microwave background radiation, providing important evidence for the early, hot expansion of the universe. Ultra-light dark photons exhibit photon-like electromagnetic interactions through kinetic mixing with photons. As a candidate for dark matter propagation in the universe, dark photons can Ultralights can display behavior similar to that of the cosmic microwave background radiation. By listening carefully with modern radio telescopes, elusive whispers can be heard from the dark world.”
Ultralight dark photons can behave similarly to dark electromagnetic fields of specific frequencies, and this research team has shown that they can be detected with radio telescopes, instruments commonly used to monitor the cosmic microwave background. In the future, their theoretical considerations could inform long-photon dark matter searches that rely on large-scale radio telescope observations.
“Our work may open up a new sub-field in radio astronomy,” he added. “We now plan to search for photon dark matter signals in the data from the LOFAR and MeerKAT telescopes. We also plan to apply this idea to search for axion dark matter, which is a very light dark matter competitive candidate.”
Haipeng An et al, Direct Detection of Photon Dark Matter Using Radio Telescopes, Physical review letters (2023). DOI: 10.1103/PhysRevLett.130.181001
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