The
big galaxy in the foreground is named LEDA 2046648, and is seen just over a
billion years back in time, while most of the others lie even farther away, and
hence are seen even further back in time. (ESA/Webb, NASA & CSA, A.
Martel)
One of the James Webb Space Telescope's principal science goals is
to observe the epoch where we think that the first galaxies were created, to
understand the details of their formation, evolution, and composition.
With each deep look back in
time, the telescope seems to break its own record for the most distant galaxy ever seen. Science papers
are now are starting to trickle in, as astronomers are finally starting to
collect enough data from JWST to build a deeper understanding of the early
Universe.
In a new study published in Nature Astronomy, a team of
researchers in Denmark believe they have observed some of the very first,
earliest galaxies with JWST.
These galaxies are so old, they
are likely still in the process of being formed.
Galaxy Ratios
One known standard is that the
ratio between galaxies and their heavy elements has held constant in the local
Universe through the last 12 billion years of history, or about 5/6 of the age
of the Universe.
But with JWST, astronomers are
now seeing that the youngest galaxies look different.
They don't have that same ratio
of stars to heavier elements because they haven't gone through the cycles of
star formation and star death yet, enriching gas clouds with metals, i.e.,
elements heavier than hydrogen and helium.
This plot shows the
observed galaxies in an "element-stellar mass diagram": The farther
to the right a galaxy is, the more massive it is, and the farther up, the more
heavy elements it contains. The gray icons represent galaxies in the present-day
Universe, while the red show the new observations of early galaxies. These ones
clearly have much less heavy elements than later galaxies, but agree roughly
with theoretical predictions, indicated by the blue band. (Kasper Elm Heintz,
Peter Laursen)
For this study, the astronomers
looked at 16 galaxies, some of the earliest galaxies ever observed. Their
observations revealed that the chemical abundances in these galaxies are
one-fourth of that seen in galaxies that were formed later.
In their paper, the astronomers wrote that "these findings suggest that galaxies at this time are still intimately connected with the intergalactic medium and subject to continuous infall of pristine gas, which effectively dilutes their metal abundances."
As gravity gathered together the first clumps of gas, the first stars and galaxies were formed.
Illustration of galaxy
formation: Diffuse gas from intergalactic space plummets toward the center,
sparking star formation and becoming part of the galaxy's rotating disk. When
stars die, they return their gas to the galaxy (and the intergalactic space),
now enriched with heavy elements. (Tumlinson et al., 2017).
"When we analyzed the
light from 16 of these first galaxies, we saw that they had significantly less
heavy elements, compared to what you'd expect from their stellar masses and the
amount of new stars they produced," said Kasper Elm Heintz, leader of the
study and assistant professor at the Cosmic Dawn Center at the Niels Bohr
Institute and DTU Space in Copenhagen, Denmark, in a press
release.
These results, the astronomers
say, are in stark contrast to the current model where galaxies evolve in a form
of equilibrium throughout most of the history of the Universe, where there is a
relationship between how many stars have formed and how many heavy elements
have formed.
Not Entirely Surprising
The researchers say, however,
this result is not entirely surprising. Theoretical models of galaxy formation
have predicted this very thing. And now it has been observed.
"The result gives us the
first insight into the earliest stages of galaxy formation which appear to be
more intimately connected with the gas in between the galaxies than we
thought," said Elm Heintz.
"This is one of the first
James Webb observations on this topic, so we're still waiting to see what the
larger, more comprehensive observations that are currently being carried out
can tell us."
The researchers said there is
no doubt that JWST will provide more data and soon they should have a much
clearer understanding of how galaxies and the first structures began their
formation during the first billion years after the Big Bang.
This article was originally
published by Universe Today. Read the original
article.
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