Astronomers turn up the heavy metal to shed light on star formation


Date:
October 6, 2020
Source:
International Centre for Radio Astronomy Research
Summary:
Astronomers have developed a new way to study star formation in
galaxies from the dawn of time to today. Using a new algorithm
to model the energy and wavelengths of light coming from almost
7000 nearby galaxies, the researchers succeeded in reconstructing
when most of the stars in the Universe formed -- in agreement with
telescope observations for the first time.



FULL STORY ========================================================================== Astronomers from The University of Western Australia's node of the International Centre for Radio Astronomy Research (ICRAR) have developed
a new way to study star formation in galaxies from the dawn of time
to today.


========================================================================== "Stars can be thought of as enormous nuclear-powered processing plants,"
said lead researcher Dr Sabine Bellstedt, from ICRAR.

"They take lighter elements like hydrogen and helium, and, over billions
of years, produce the heavier elements of the periodic table that we
find scattered throughout the Universe today.

"The carbon, calcium and iron in your body, the oxygen in the air you
breathe, and the silicon in your computer all exist because a star
created these heavier elements and left them behind," Bellstedt said.

"Stars are the ultimate element factories in the Universe." Understanding
how galaxies formed stars billions of years ago requires the very
difficult task of using powerful telescopes to observe galaxies many
billions of light-years away in the distant Universe.



========================================================================== However, nearby galaxies are much easier to observe. Using the light
from these local galaxies, astronomers can forensically piece together
the history of their lives (called their star-formation history). This
allows researchers to determine how and when they formed stars in their infancy, billions of years ago, without struggling to observe galaxies
in the distant Universe.

Traditionally, astronomers studying star formation histories assumed
the overall metallicity -- or amount of heavy elements -- in a galaxy
doesn't change over time.

But when they used these models to pinpoint when stars in the Universe
should have formed, the results didn't match up with what they were
seeing through their telescopes.

"The results not matching up with our observations is a big problem,"
Bellstedt said. "It tells us we're missing something." "That missing ingredient, it turns out, is the gradual build-up of heavy metals
within galaxies over time." Using a new algorithm to model the energy
and wavelengths of light coming from almost 7000 nearby galaxies, the researchers succeeded in reconstructing when most of the stars in the
Universe formed -- in agreement with telescope observations for the
first time.



==========================================================================
The designer of the new code -- known as ProSpect -- is Associate
Professor Aaron Robotham from ICRAR's University of Western Australia
node.

"This is the first time we've been able to constrain how the heavier
elements in galaxies change over time based on our analysis of these
7000 nearby galaxies," Robotham said.

"Using this galactic laboratory on our own doorstep gives us lots of observations to test this new approach, and we're very excited that
it works.

"With this tool, we can now dissect nearby galaxies to determine the
state of the Universe and the rate at which stars form and mass grows
at any stage over the past 13 billion years.

"It's absolutely mind-blowing stuff." This work also confirms an
important theory about when most of the stars in the Universe formed.

"Most of the stars in the Universe were born in extremely massive galaxies early on in cosmic history -- around three to four billion years after
the Big Bang," Bellstedt said.

"Today, the Universe is almost 14 billion years old, and most new stars
are being formed in much smaller galaxies." Based on this research,
the next challenge for the team will be to expand the sample of galaxies
being studied using this technique, in an effort to understand when,
where and why galaxies die and stop forming new stars.

Bellstedt and Robotham, along with colleagues from Australia, the UK
and the United States, are reporting their results in the scientific
journal the Monthly Notices of the Royal Astronomical Society.


========================================================================== Story Source: Materials provided by International_Centre_for_Radio_Astronomy_Research. Note: Content may be
edited for style and length.


========================================================================== Journal Reference:
1. Sabine Bellstedt, Aaron S G Robotham, Simon P Driver, Jessica
E Thorne,
Luke J M Davies, Claudia del P Lagos, Adam R H Stevens, Edward
N Taylor, Ivan K Baldry, Amanda J Moffett, Andrew M Hopkins,
Steven Phillipps.

Galaxy And Mass Assembly (GAMA): a forensic SED reconstruction
of the cosmic star formation history and metallicity evolution by
galaxy type.

Monthly Notices of the Royal Astronomical Society, 2020; 498 (4):
5581 DOI: 10.1093/mnras/staa2620 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/10/201006114245.htm

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