New galaxy images reveal a fitful start to the Universe

Date:
October 20, 2021
Source:
University of Nottingham
Summary:
New images have revealed detailed clues about how the first stars
and structures were formed in the Universe and suggest the formation
of the Galaxy got off to a fitful start.



FULL STORY ==========================================================================
New images have revealed detailed clues about how the first stars and structures were formed in the Universe and suggest the formation of the
Galaxy got off to a fitful start.


==========================================================================
An international team of astronomers from the University of Nottingham and Centro de Astrobiologi'a (CAB, CSIC-INTA) used data from the Hubble Space Telescope (HST) and the Gran Telescopio Canarias (GTC), the so-called
Frontier Fields, to locate and study some of the smallest faintest
galaxies in the nearby universe. This has revealed the formation of the
galaxy was likely to be fitful. The first results have just been published
in the journal Monthly Notices of the Royal Astronomical Society (MNRAS).

One of the most interesting questions that astronomers have been trying to answer for decades is how and when the first galaxies formed. Concerning
the how, one possibility is that the formation of the first stars within galaxies started at a steady pace, slowly building up a more and more
massive system.

Another possibility is that the formation was more violent and
discontinuous, with intense, but short lived bursts of star formation
triggered by events such as mergers and enhanced gas accretion.

"Galaxy formation can be compared to a car," explains Pablo G. Pe'rez- Gonza'lez, one of the co-authors of the paper, affiliated to the Centro
de Astrobiologi'a (CAB/CSIC-INTA) in Spain, and principal investigator of
the international collaboration behind this study. "The first galaxies
might have had a 'diesel' star-forming engine, slowly but continuously
adding up new stars, without much acceleration and gently turning gas
into relatively small stars for long periods of time. Or the formation
could have been jerky, with bursts of star formation producing incredibly
large stars that disrupt the galaxy and make it cease its activity for a
while or even forever. Each scenario is linked to different processes,
such as galaxy mergers or the influence of supermassive black holes,
and they have an effect on when and how the carbon or oxygen, that are essential for our life, formed." Using the gravitational lensing power of
some of the Universe's most massive galaxy clusters with the exceptional
GTC data coming from a project entitled the Survey for high-z Red and
Dead Sources (SHARDS) the astronomers searched for nearby analogs of
the very first galaxies formed in the Universe, so that they could be
studied in much more detail.

Dr Alex Griffiths from the University Nottingham was one of the
lead UK researchers on the study, he explains: "Until we have the
new James Webb Space telescope, we cannot observe the first galaxies
ever formed, they are just too faint. So we looked for similar beasts
in the nearby Universe and we dissected them with the most powerful
telescopes we currently have." The researchers combined the power
of the most advanced telescopes, such as HST and GTC, with the aid of
"natural telescopes." Professor Chris Conselice, from the University of Manchester is a co-author on the study, he said: "Some galaxies live in
large groups, what we call clusters, which contain huge amounts of mass
in the form of stars, but also gas and dark matter. Their mass is so
large that they bend space-time, and act as natural telescopes. We call
them gravitational lenses and they allow us to see faint and distant
galaxies with enhanced brightness and at a higher spatial resolution." Observations of some of these massive clusters acting as gravitational telescopes is the base of the Frontier Field survey. The study showed that
the formation of the galaxy was likely to be stop-start with bursts of
activity followed by lulls. Dr Griffiths from the University of Nottingham said: "Our main result is that the start of galaxy formation is fitful,
like a jerky car engine, with periods of enhanced star formation followed
by sleepy intervals.

It is unlikely that galaxy mergers have played a substantial role in
the triggering of these bursts of star formation and it is more likely
due to alternative causes that enhance gas accretion, we need to search
for those alternatives.

"We were able to find these objects due to the high quality SHARDS data
coupled with imaging data from the Hubble Space Telescope to detect
hot gas heated by newly formed stars in very small galaxies. This hot
gas emits in certain wavelengths, what we call emission lines, just as
a neon light. Analysing these emission lines can provide an insight
into the formation and evolution of a galaxy." "The SHARDS Frontier
Fields observations carried out with GTC have provided the deepest data
ever taken for discovering dwarf galaxies through their emission lines, allowing us to identify systems with recently triggered star formation,"
adds Pe'rez-Gonza'lez, one of the co-authors of the paper and principal investigator of the GTC SHARDS Frontier Fields project.

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


========================================================================== Journal Reference:
1. Alex Griffiths, Christopher J Conselice, Leonardo Ferreira, Daniel
Ceverino, Daniel Rosa-Gonza'lez et al. Emission line galaxies in the
SHARDS Frontier Fields - I. Candidate selection and the discovery
of bursty Ha emitters. Monthly Notices of the Royal Astronomical
Society, 2021 DOI: 10.1093/mnras/stab2566 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/10/211020203707.htm

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