Could dark photon dark matter be directly detected using radio telescopes?

Dark matter cannot be directly observed by using normal telescopes or other imaging methods since it does not emit, absorb, or reflect light. Thus, astronomers have been looking for alternate ways to find dark matter for decades.

A recent investigation by scientists from Tsinghua University, Purple Mountain Observatory, and Peking University looked at the potential for directly detecting dark photons—prominent dark matter candidates—using radio telescopes. Their study, which was published in Physical Review Letters, may help future efforts to find dark photons, which are fictitious particles that transmit an electric and magnetic field in dark matter, much like photons do in ordinary matter.

According to Haipeng An, one of the study's authors, "our prior work examined the conversion of dark photons into photons in the solar corona."

"In this process, free electrons are excited by dark photon fields, which causes the emission of regular photons. Based on this study, Jia and I discussed the possibility of creating electromagnetic signals with free electrons in a dish telescope and then searching for such signals with the FAST telescope.

An and his colleagues soon realized that, given the non-relativistic nature of dark matter, the reflector in such telescopes would need to be spherical and the receiver of the signal should be positioned at the center of this sphere. Shortly after they began investigating the use of dish telescopes to look for electromagnetic signals related to dark photons, An and his colleagues.

The receiver is positioned near the point of focus of existing dished radio telescopes, such as the five-hundred-meter aperture spherical radio telescope (FAST) in China, which are made to observe distant radio waves.

This meant that dark photon-induced electromagnetic signals would not concentrate at their receiver.

We momentarily abandoned this notion after this understanding, An said. I was asked to present lectures on dark matter at the UFITS summer school for cosmology conducted at the FAST site in the summer of 2021. During this time, I also carefully examined the FAST telescope's operation. I discovered that the telescope could view radio waves coming from various directions by moving the receiver that was suspended above the dish. Then, I had the thought that, despite the fact that the dark photon dark matter-induced electromagnetic waves are not focused on the receiver, the electromagnetic field can nonetheless create a distribution on top of the dish that can be precisely computed theoretically.

The moveable receiver in radio telescopes should be able to gather electromagnetic signals in various locations, according to An's subsequent theoretical predictions. The sensitivity of the telescopes to dark photon-induced signals might then be increased by comparing the distributions of the signals gathered by the receiver to those anticipated by theory.

Then, An said, "We began to calculate this signal with our colleagues." To our surprise, we discovered that the FAST telescope's sensitivity has already surpassed the CMB constraint, even without taking into account the distribution or the extraordinary sensitivity, or the fact that the dark photon dark matter induced signal is not focused at the receiver. This means that the FAST telescope can find the dark matter if it is made up of dark photons and is in the appropriate mass range.

An and his colleagues also examined observation data gathered by the FAST radio telescope, which is situated in a hamlet in the mountains in the Guizhou area of China, in order to further evaluate the efficacy of their suggested approach to look for dark photons. Prof. Xiaoyuan Huang, who is also a co-author of the latest article, gave this information.

An said, "We examined the data and set the tightest restriction on the model in the frequency band of 1-1.5 GHz. We calculated the potential sensitivity of the LOFAR telescope and the future SKA telescope and found they both have the potential to discover dark photon dark matter. "We realized that dark photon dark matter could induce electric signals on dipole antennas and that due to the non-relativistic nature, we could use interferometry technology to improve the sensitivity.

Overall, the assessments performed by this research team point to the possibility of using radio telescopes to directly detect dark photons. Thus, this research may open up new avenues for the ongoing hunt for dark photons, especially ultra-light dark photons.

An said that Penzias and Wilson came into an unanticipated low-level background noise in the early 1960s while working on radio astronomy research. "This cacophony was eventually determined to represent the cosmic microwave background radiation, giving crucial proof of the very hot early universe's expansion. Through kinetic mixing with photons, ultra-light dark photons display electromagnetic interactions similar to photons. Ultra-light dark photons may behave like cosmic microwave background radiation as a possibility for diffuse dark matter in the cosmos. Modern radio telescopes may be used to carefully listen for the elusive murmurs coming from the dark realm.

This study team demonstrated that ultralight dark photons might possibly be discovered using radio telescopes, which are frequently used to monitor the cosmic microwave background. Ultralight dark photons can behave similarly to dark electromagnetic fields with certain frequencies. Future studies for dark photon dark matter that rely on extensive radio telescope data may be guided by their theoretical concerns.

"Our work may open a new sub-area in radio astronomy," An further stated. The data from the LOFAR and MeerKAT telescopes will now be used to look for dark photon dark matter signatures. Additionally, we want to use this concept to look for axion dark matter, another viable possibility for ultralight dark matter.