A new study led by UC Riverside graduate student Yash Aggarwal argues that decays of dark matter could help explain very large black holes seen less than a billion years after the Big Bang. The paper appears in the Journal of Cosmology and Astroparticle Physics.
The researchers show that energy from decaying dark matter can alter the thermo-chemical state of gas in the first galaxies. These changes can allow some gas clouds to collapse directly into black holes rather than forming stars. Previously, astronomers thought direct collapse needed a rare nearby star to shine on the gas.
The team modelled the gas behaviour with decaying axions and found a window of dark matter masses between 24 and 27 electronvolts could favour direct collapse. The work involved several collaborators and received support from research funders.
Difficult words
- decay — process where a particle breaks down over timedecays, decaying
- dark matter — invisible matter that affects gravity in space
- thermo-chemical — relating to heat and chemical processes in gas
- collapse — fall together quickly into a smaller object
- axion — a hypothetical very light particle in physicsaxions
- electronvolt — unit that measures very small energy amountselectronvolts
- galaxy — a large system of stars, gas and dustgalaxies
Tip: hover, focus or tap highlighted words in the article to see quick definitions while you read or listen.
Discussion questions
- Do you think decaying dark matter is a convincing explanation for early large black holes? Why or why not?
- If some gas clouds collapse directly into black holes, how might that change the first galaxies?
- What other observations or evidence would you want to see to support this study's idea?
