by A trove of molecules has emerged in two galaxies we see as they were over 12 billion years ago, revealing information about how the ancient realms formed stars.
One of the distant galaxies, APM 08279+5255, is home to a quasar — active supermassive black hole at its core engulfing huge amounts of gas — and the other, NCv1.143, is a more “normal” galaxy. Both, however, appear to be forming stars at a ferocious rate, hundreds of times more stars than the The Milky Way Galaxy currently generating.
Astronomers focused on the two galaxies using NOEMA, the Northern Extended Millimeter Array, in France. NOEMA is capable of detecting millimeter and sub-millimeter radio waves. Amazingly, the team, led by Chentao Yang from Chalmers University of Technology in Sweden, detected emissions from 13 different molecules in these two galaxies.
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“Some of the electromagnetic spectrum that’s hard to notice in nearby galaxies,” Yang said in a press release. “But thanks to the expansion of the universelight from distant galaxies like this is converted to longer wavelengths that we can see with radio telescopes [at] submillimeter [wavelengths].”
The discovery is the largest collection of molecules ever detected in galaxies so far away (there are now about 20 billion galaxies light year away, and getting further due to cosmic expansion).
Among the 13 different types of molecules detected are carbon monoxide, carbon monoxide, the cyano radical (a radical is an unpaired molecule). electron in the outer shell of one of its constituents), the formula cation (positively charged ion), hydrogen cyanide, hydrogen isocyanide, nitric oxide and water. Yang’s team also detected five previously unseen molecules in the early universe: Cyclopropenylidene (a highly reactive organic molecule also found on Saturnand moon Titan), diazenylium (made of molecular nitrogen and a hydrogen ion), radicals of the organic molecule ethynyl, hydrogen ions (formed from a molecule of water and a hydrogen ion) and radicals of methylene (a highly reactive organic molecule).
All of these molecules are commonly found in interstellar gas in our Milky Way galaxy, and each provides clues about the environment in which they are found – an environment that we see many stars forming.
“We knew that the galaxies were prodigious star factories, perhaps among the largest that the universe has ever seen,” said Yang.
The team also found that the quasar in APM 08279+5255 contains more excited molecular gas with higher temperatures and densities than NCv1.143 as a whole, possibly a consequence of the activity around the quasar’s black hole. Their molecular abundances are similar to active galaxies black holes in the more modern universe. Similarly, the molecular inventory of the NCv1.143 is similar to local constellation galaxies, which are only galaxies that yield many stars, such as the Cigar Galaxy (Messier 82) in the constellation of Ursa Major, the Great Bear. It appears that the chemistry of these types of galaxies was already in place 12 billion years ago.
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But not everything is the same. The strength of the emission from some of the molecules, such as carbon dioxide, combined with the extreme conditions in the star-forming gas of both galaxies, gives what is called a “top-heavy initial mass function.” The initial mass function, or IMF, describes how many stars of a given mass are capable of forming, and low-mass stars are much more common than high-mass stars. A top-heavy CAI would imply that more massive stars were able to form in the early universe than can form today. This could not only explain why early galaxies in the universe are being detected by the James Webb Space Telescope brighter than expected — that they contain more massive and brighter stars — but they also indicate that there are more massive stars that explode as supernova accelerate the development of chemistry in these galaxies, distributing heavy elements across space.
“The most prominent galaxies in the early universe are finally able to tell their stories through their molecules,” said co-author Pierre Cox, from Sorbonne Université in France.
The results were published on 14 December in the journal Astronomy and Astrophysics.
