Astronomers have made a groundbreaking discovery about small, red galaxies known as “little red dots.” Using the James Webb Space Telescope, researchers found that these galaxies are more abundant than previously thought and formed earlier than expected. The new findings also suggest that these galaxies may help identify how the earliest black holes came to be.
The term “little red dots” was initially used to describe galaxies that seemed too massive to have formed early on in the universe’s history. However, a team led by Dale Kocevski discovered that these galaxies are actually host to hungry black holes that guzzle gas and emit more light than all of the galaxy’s stars.
Kocevski analyzed over 1,000 JWST images, which yielded a sample of 341 little red dots. The team also combined data from other surveys, finding that more than 80% of LRDs showed signs of gas and dust spiraling at high speeds around central black holes. This solid evidence confirms that the little red dots are indeed active galactic nuclei (AGN).
The discovery challenges a key theory about galaxy formation, which suggests that big black holes live in big galaxies while small ones reside in small galaxies. However, if these small galaxies host massive black holes, it could support the direct collapse theory, which proposes that early black holes were formed from massive dust collapses.
According to Kocevski, LRDs represent 1-5% of all galaxies in the early universe, more than 10 times the expected number for galaxies hosting gas-guzzling black holes. The team estimates that these galaxies are most common when the universe was around 800 million years old, before dropping off at around 1.6 billion years.
While LRDs still hold some mysteries, such as not emitting X-rays like typical AGN, the new research provides a significant insight into their nature and behavior. Kocevski notes that if you look at an image of the early universe with JWST, you’re likely to see “a handful of little red dots” in every frame, highlighting the need for further study on these enigmatic galaxies.
Source: https://skyandtelescope.org/astronomy-news/little-red-dots-early-black-hole-formation