Astronomers make most distant detection yet of fluorine in star-forming
galaxy

Date:
November 4, 2021
Source:
ESO
Summary:
A new discovery is shedding light on how fluorine -- an element
found in our bones and teeth as fluoride -- is forged in the
Universe. Astronomers have detected this element in a galaxy that
is so far away its light has taken over 12 billion years to reach
us. This is the first time fluorine has been spotted in such a
distant star-forming galaxy.



FULL STORY ==========================================================================
A new discovery is shedding light on how fluorine -- an element found
in our bones and teeth as fluoride -- is forged in the Universe. Using
the Atacama Large Millimeter/submillimeter Array (ALMA), in which the
European Southern Observatory (ESO) is a partner, a team of astronomers
have detected this element in a galaxy that is so far away its light has
taken over 12 billion years to reach us. This is the first time fluorine
has been spotted in such a distant star-forming galaxy.


==========================================================================
"We all know about fluorine because the toothpaste we use every day
contains it in the form of fluoride," says Maximilien Franco from the University of Hertfordshire in the UK, who led the new study, published
today in Nature Astronomy. Like most elements around us, fluorine
is created inside stars but, until now, we did not know exactly how
this element was produced. "We did not even know which type of stars
produced the majority of fluorine in the Universe!" Franco and his collaborators spotted fluorine (in the form of hydrogen fluoride) in
the large clouds of gas of the distant galaxy NGP-190387, which we see
as it was when the Universe was only 1.4 billion years old, about 10%
of its current age. Since stars expel the elements they form in their
cores as they reach the end of their lives, this detection implies that
the stars that created fluorine must have lived and died quickly.

The team believes that Wolf-Rayet stars, very massive stars that live
only a few million years, a blink of the eye in the Universe's history,
are the most likely production sites of fluorine. They are needed
to explain the amounts of hydrogen fluoride the team spotted, they
say. Wolf-Rayet stars had been suggested as possible sources of cosmic
fluorine before, but astronomers did not know until now how important
they were in producing this element in the early Universe.

"We have shown that Wolf-Rayet stars, which are among the most massive
stars known and can explode violently as they reach the end of their
lives, help us, in a way, to maintain good dental health!" jokes Franco.

Besides these stars, other scenarios for how fluorine is produced
and expelled have been put forward in the past. An example includes
pulsations of giant, evolved stars with masses up to few times that of
our Sun, called asymptotic giant branch stars. But the team believes
these scenarios, some of which take billions of years to occur, might
not fully explain the amount of fluorine in NGP-190387.

"For this galaxy, it took just tens or hundreds of millions of years to
have fluorine levels comparable to those found in stars in the Milky
Way, which is 13.5 billion years old. This was a totally unexpected
result," says Chiaki Kobayashi, a professor at the University of
Hertfordshire. "Our measurement adds a completely new constraint
on the origin of fluorine, which has been studied for two decades."
The discovery in NGP-190387 marks one of the first detections of fluorine beyond the Milky Way and its neighbouring galaxies. Astronomers have
previously spotted this element in distant quasars, bright objects
powered by supermassive black holes at the centre of some galaxies. But
never before had this element been observed in a star-forming galaxy so
early in the history of the Universe.

The team's detection of fluorine was a chance discovery made possible
thanks to the use of space and ground-based observatories. NGP-190387, originally discovered with the European Space Agency's Herschel
Space Observatory and later observed with the Chile-based ALMA, is extraordinarily bright for its distance. The ALMA data confirmed that the exceptional luminosity of NGP-190387 was partly caused by another known
massive galaxy, located between NGP-190387 and the Earth, very close to
the line of sight. This massive galaxy amplified the light observed by
Franco and his collaborators, enabling them to spot the faint radiation
emitted billions of years ago by the fluorine in NGP-190387.

Future studies of NGP-190387 with the Extremely Large Telescope (ELT) --
ESO's new flagship project, under construction in Chile and set to start operations later this decade -- could reveal further secrets about this
galaxy. "ALMA is sensitive to radiation emitted by cold interstellar
gas and dust," says Chentao Yang, an ESO Fellow in Chile. "With the
ELT, we will be able to observe NGP- 190387 through the direct light of
stars, gaining crucial information on the stellar content of this galaxy." ========================================================================== Story Source: Materials provided by ESO. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. M. Franco, K. E. K. Coppin, J. E. Geach, C. Kobayashi,
S. C. Chapman, C.

Yang, E. Gonza'lez-Alfonso, J. S. Spilker, A. Cooray & M. J.

Michałowski. The ramp-up of interstellar medium enrichment
at z > 4.

Nature Astronomy, 2021 DOI: 10.1038/s41550-021-01515-9 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/11/211104121307.htm

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