Astronomers team up to create new method to understand galaxy evolution
A husband-and-wife team of astronomers established the star formation
history of a post-starburst galaxy using its cluster population.

Date:
November 16, 2021
Source:
University of Toledo
Summary:
A husband-and-wife team of astronomers joined forces for the first
time in their scientific careers during the pandemic to develop a
new method to look back in time and change the way we understand
the history of galaxies.



FULL STORY ==========================================================================
A husband-and-wife team of astronomers at The University of Toledo
joined forces for the first time in their scientific careers during the pandemic to develop a new method to look back in time and change the
way we understand the history of galaxies.


========================================================================== Until now forging parallel but separate careers while juggling home
life and carpooling to cross country meets, Dr. Rupali Chandar,
professor of astronomy, and Dr. J.D. Smith, director of the UToledo
Ritter Astrophysical Research Center and professor of astronomy, merged
their areas of expertise.

Working along with UToledo alumnus Dr. Adam Smercina who graduated with
a bachelor's degree in physics in 2015 and is currently a postdoctoral researcher at the University of Washington, they used NASA's Hubble
Space Telescope to focus on a post-starburst galaxy nearly 500 million
light years away called S12 that looks like a jellyfish with a host of
stars streaming out of the galaxy on one side.

Smercina, the "glue" that brought Smith and Chandar together on this
research, worked with Smith as an undergraduate student starting in 2012
on the dust and gas in post-starburst galaxies.

While spiral galaxies like our Milky Way have continued to form stars
at a fairly steady rate, post-starburst galaxies experienced an intense
burst of star formation sometime in the last half billion years, shutting
down their star formation.

The resulting breakthrough research published in the Astrophysical Journal outlines their new method to establish the star formation history of a
post- starburst galaxy using its cluster population. The approach uses the
age and mass estimates of stellar clusters to determine the strength and
speed of the starburst that stopped more stars from forming in the galaxy.



========================================================================== Using this method, the astronomers discovered that S12 experienced two
periods of starburst before it stopped forming stars, not one.

"Post-starbursts represent a phase of galaxy evolution that is pretty
rare today," Smith said. "We think that nearly half of all galaxies
went through this phase at some point in their lives. So far, their star-forming histories have been determined almost exclusively from
detailed modeling of their composite starlight." Smith has studied post-starburst galaxies for more than a decade, and Chandar works on
the stellar clusters in galaxies that are typically about three or four
times closer than those in Smith's data.

"Clusters are like fossils -- they can be age-dated and give us clues
to the past history of galaxies," Chandar said. "Clusters can only be
detected in these galaxies with the clear eyed-view of the Hubble Space Telescope. No clusters can be detected in even the highest quality
images taken with telescopes on the ground." Smith has led several
large multi-wavelength projects to better understand the evolutionary
history of post-starburst galaxies. He discovered, for example, that
the raw fuel for star formation -- gas and dust -- is still present
in surprising quantities in some of these systems including S12, even
though no stars are currently being formed.



========================================================================== "While studying the light from these galaxies at multiple wavelengths has helped establish the time that the burst happened, we hadn't been able to determine how strong and how long the burst that shutoff star formation actually was," Smith said. "And that's important to know to better
understand how these galaxies evolve." The astronomers used well-studied cluster masses and star formation rates in eight nearby galaxies to
develop the new method, which could be applied to determine the recent
star formation histories for a number of post-starburst systems.

The researchers applied their different approach to S-12, which is short
for SDSS 623-52051-207, since it was discovered and catalogued in the
Sloan Digitized Sky Survey (SDSS).

"It must have had one of the highest rates of star formation of any
galaxy we have ever studied," Chandar said. "S12 is the most distant
galaxy I've ever worked on." The study indicates star formation in S12
shut off 70 million years ago after a short but intense burst formed
some of the most massive clusters known, with masses several times higher
than similar-age counterparts forming in actively merging galaxies. The
method also revealed an earlier burst of star formation that the previous method of composite starlight modeling could not detect.

"These results suggest that S12's unusual history may be even more
complicated than expected, with multiple major events compounding to
fully shut off star formation," Smith said.

The research was funded by the National Science Foundation and NASA.

Chandar and Smith are two of four UToledo astronomers leading some of
the first research projects on NASA's new James Webb Space Telescope
scheduled to launch in December.

========================================================================== Story Source: Materials provided by University_of_Toledo. Original written
by Christine Billau. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Rupali Chandar, Angus Mok, K. Decker French, Adam Smercina,
John-David T.

Smith. The Star Formation History of a Post-starburst Galaxy
Determined from Its Cluster Population. The Astrophysical Journal,
2021; 920 (2): 105 DOI: 10.3847/1538-4357/ac0c19 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/11/211116103112.htm

--- up 5 days, 2 hours, 55 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)