How stars form in the smallest galaxies

Date:
August 12, 2020
Source:
Lund University
Summary:
The question of how small, dwarf galaxies have sustained the
formation of new stars over the course of the Universe has long
confounded the world's astronomers. An international research
team has found that dormant small galaxies can slowly accumulate
gas over many billions of years. When this gas suddenly collapses
under its own weight, new stars are able to arise.



FULL STORY ==========================================================================
The question of how small, dwarf galaxies have sustained the formation of
new stars over the course of the Universe has long confounded the world's astronomers. An international research team led by Lund University in
Sweden has found that dormant small galaxies can slowly accumulate gas
over many billions of years. When this gas suddenly collapses under its
own weight, new stars are able to arise.


========================================================================== There are around 2,000 billion galaxies in our Universe and, while our
own Milky-Way encompasses between 200 and 400 billion stars, small dwarf galaxies contain only a thousand times less. How stars are formed in
these tiny galaxies has long been shrouded in mystery.

However, in a new study published in the research journal Monthly
Notices of the Royal Astronomical Society, a research team led from
Lund University has established that dwarf galaxies are capable of lying dormant for several billion years before starting to form stars again.

"It is estimated that these dwarf galaxies stopped forming stars around 12 billion years ago. Our study shows that this can be a temporary hiatus,"
says Martin Rey, an astrophysicist at Lund University and the leader of
the study.

Through high-resolution computer simulations, the researchers demonstrate
that star formation in dwarf galaxies ceased as a result of the heating
and ionisation from the strong light of newborn stars. Explosions of
so-called white dwarfs -- small faint stars made of the core that remains
when normal- sized stars die -further contribute in preventing the star formation process in dwarf galaxies.

"Our simulations show that dwarf galaxies are able to accumulate fuel in
the form of gas, which eventually condenses and gives birth to stars. This explains the observed star formation in existing faint dwarf galaxies
that has long puzzled astronomers," states Martin Rey.

The computer simulations used by the researchers in the study are
amongst the most expensive that can be carried out within physics. Each simulation takes as long as two months and requires the equivalent of
40 laptop computers operating around the clock. The work is continuing
with the development of methods to better explain the processes behind
star formation in our Universe's smallest galaxies.

"By deepening our understanding of this subject, we gain new insights
into the modelling of astrophysical processes such as star explosions,
as well as the heating and cooling of cosmic gas. In addition, further
work is underway to predict how many such star-forming dwarfs exist
in our Universe, and could be discovered by astronomical telescopes"
concludes Martin Rey.


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


========================================================================== Journal Reference:
1. Martin P Rey, Andrew Pontzen, Oscar Agertz, Matthew D A Orkney,
Justin I
Read, Joakim Rosdahl. EDGE: from quiescent to gas-rich to
star-forming low-mass dwarf galaxies. Monthly Notices of
the Royal Astronomical Society, 2020; 497 (2): 1508 DOI:
10.1093/mnras/staa1640 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200812144106.htm

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