Galaxies, like our Milky Way galaxy, are collections of billions of stars held together by gravity. Sometimes galaxies clump together in clusters containing hundreds or even thousands of galaxies. These galaxy clusters are the largest objects in the Universe that are held together by their own gravity, and they take billions of years to form and change. If we could somehow watch their evolution in fast-forward, we wouldn’t need movies — the dramatic interactions between galaxies would keep us mesmerized. But there is a way we can read the stories of galaxy cluster history, and our cosmic storyteller is the population of stars that have been stripped from their home galaxies and strewn into the spaces between galaxies in the cluster. These stars give off a ghostly glow called intracluster light, and it’s at least 1000 times fainter than the darkest night sky we can perceive with our eyes. Intracluster light has stayed mostly hidden from existing telescopes and cameras because it’s so faint. But with the data from Vera C. Rubin Observatory’s Legacy Survey of Space and Time, which will begin in 2025, scientists will be able to observe this extremely faint light like never before.
Rubin Observatory is jointly funded by the U.S. National Science Foundation (NSF) and the US Department of Energy (DOE). Rubin is a Program of NSF’s NOIRLab, and SLAC National Accelerator Laboratory, which will jointly operate Rubin.
Over millions of years, as galaxies collide and merge,
intracluster light forms a ‘fossil record’ of the dynamical
interactions a galaxy cluster has experienced, offering a wealth of
information about the history of the cluster system and the history of
the Universe on large scales.
“Stars stripped from their galaxies end up populating the space
between galaxies in a cluster. These stars are like the dust released
from a piece of chalk when you write on a blackboard.” says Mireia Montes, research fellow at Instituto de Astrofísica de Canarias and member of the Rubin/LSST Galaxies Science Collaboration. "By tracking the stellar chalk dust with Rubin, we hope to be able to read the words on the galaxy cluster blackboard."
>How many of a galaxy cluster’s stars are actually free-floating,
contributing to the glow? How are they distributed in the cluster? The
answers to these questions aren’t well known, because intracluster light
has been so difficult to study until now. “There’s so much we don’t know about intracluster light,” says Montes. “The power of Rubin is that it’s going to provide us with lots of clusters of galaxies that we can explore.”
In addition to studying intracluster light for clues about the
history of galaxy clusters, scientists can also use it to gain insight
about the elusive substance known as dark matter — an invisible material that doesn’t emit or reflect light and is found in high concentrations around clusters of galaxies.
Rubin will scan the entire southern hemisphere sky every few nights for ten years with the largest digital camera in the world,
revealing intracluster light that, until now, astronomers have largely
been able to detect only with long and targeted observations of one
galaxy cluster at a time. Over the course of its 10-year survey, Rubin
will take millions of high-resolution images of distant galaxy clusters,
and scientists will be able to stack these images together into the
largest ultra-long-exposure images ever created of the southern
hemisphere sky. The stacked images will give scientists more galaxy
clusters with detectable intracluster light in each field of view than they've had in total
to date. In this way, Rubin will expand the number of galaxy clusters
we can study from just a handful to thousands, which will allow
researchers like Montes to analyze the faint glow of intracluster light
across the Universe.
From the evolution of galaxy clusters to the distribution of dark
matter, intracluster light holds important clues about how the
large-scale structure of the Universe came to be. “Intracluster light may look like something very small and insignificant, but it has a lot of implications,” Montes says. “It complements what we already know, and will open new windows into the history of our Universe.”
More information
The US National Science Foundation (NSF) is an independent federal
agency created by Congress in 1950 to promote the progress of science.
NSF supports basic research and people to create knowledge that
transforms the future.
DOE’s Office of Science
is the single largest supporter of basic research in the physical
sciences in the United States and is working to address some of the most
pressing challenges of our time.
NSF’s NOIRLab (National
Optical-Infrared Astronomy Research Laboratory), the US center for
ground-based optical-infrared astronomy, operates the international Gemini Observatory (a facility of NSF, NRC–Canada, ANID–Chile, MCTIC–Brazil, MINCyT–Argentina, and KASI–Republic of Korea), Kitt Peak National Observatory (KPNO), Cerro Tololo Inter-American Observatory (CTIO), the Community Science and Data Center (CSDC), and Vera C. Rubin Observatory (in cooperation with DOE’s SLAC National Accelerator Laboratory). It is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with NSF
and is headquartered in Tucson, Arizona. The astronomical community is
honored to have the opportunity to conduct astronomical research on
Iolkam Du’ag (Kitt Peak) in Arizona, on Maunakea in Hawai‘i, and on
Cerro Tololo and Cerro Pachón in Chile. We recognize and acknowledge the
very significant cultural role and reverence that these sites have to
the Tohono O’odham Nation, to the Native Hawaiian community, and to the
local communities in Chile, respectively.
Links
Contacts
Mireia Montes
Member of the Rubin/LSST Galaxies Science Collaboration
Email: mmontes@iac.es
Kristen Metzger
Communications Manager for Education and Public Outreach, Rubin Observatory
Email: kristen.metzger@noirlab.edu
Bob Blum
Director for Operations, Vera C. Rubin Observatory, NSF’s NOIRLab
Tel: +1 520-318-8233
Email: bob.blum@noirlab.edu
Željko Ivezić
Professor of Astronomy, University of Washington/AURA
Tel: +1-206-403-6132
Email: ivezic@uw.edu
Josie Fenske
Communications NSF’s NOIRLab
Email: fenske.josie@noirlab.edu
Manuel Gnida
Media Relations Manager, SLAC National Accelerator Laboratory
Tel: +1 650-926-2632 (office)
Cell: +1 415-308-7832 (cell)
Email: mgnida@slac.stanford.edu
