Dark Energy SpectrophotometerDESI) finished the first seven months of their search, shattering all previous records of 3D galactic surveys, and creating the largest and most detailed map of the universe ever made. However, he only came close 10% of the way during his five-year mission. Once completed, this highly detailed 3D map will lead to a better understanding of dark energy, giving physicists and astronomers a better understanding of the universe’s past and future. Meanwhile, the amazing technical performance and cosmic achievements of research so far are helping scientists to unravel the secrets of the most powerful sources of light in the universe.
DESI is an international scientific collaboration managed by the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Laboratory) with seed funding for construction and operations from the Department of Energy’s Office of Science.
DESI scientists are presenting device performance and some early astrophysics results this week at a webinar hosted by Berkeley Lab called CosmoPalooza, which will also feature updates from other groundbreaking cosmic experiments.
“There’s a lot of beauty in that,” said Julian Gay, a scientist at Berkeley Lab, one of the speakers. “In the distribution of galaxies on the 3D map, there are huge clusters, filaments and voids. They are the largest structures in the universe. But inside them, you find an imprint of the early universe and the history of its expansion. Since then.”
DESI has come a long way to get to this point. It was originally proposed more than a decade ago and construction of the device began in 2015. It is installed on the 4-meter Nicholas U Maywell Telescope at Kate Summit Observatory near Tucson, Arizona. The Kit Summit National Observatory is the NOIRLab program of the National Science Foundation (NSF), which was contracted by the Department of Energy to operate the Mayall Telescope for the DESI survey. The device saw its first light in late 2019. Then, during its validation phase, the coronavirus pandemic hit and the telescope was closed for several months, although some remote work continued. In December 2020, DESI turned its attention to the sky again, tested its hardware and software, and in May 2021, it was ready to begin scientific research.
Scroll through the completed Sloan Digital Sky Survey 3D galaxy map.
A slice of a 3D map of galaxies from the first few months of dark energy spectroscopy (DESI; right). Earth is located in the center and is more than 10 billion light-years away from it. Each point represents a galaxy. This 2D slice of the 3D DESI map shows only about 800,000 of the 7.5 million galaxies currently scanned, which by itself is just a fraction of the 35 million galaxies that will be on the final map. Credit: D. Schlegel/Berkeley Lab using DESI data
But work on DESI itself was not complete when the research began. “It’s work in progress to make this tool work,” said Ohio State University physicist Klaus Hünscheid, a machine scientist involved in the project, who will present the first paper for the CosmoPalooza DESI session. Honscheid and his team ensure that the tool runs smoothly and automatically, ideally without any interference during nighttime monitoring. “The feedback I get from night watchers is that shifts are boring, and I take that as a compliment,” he said.
But this monotonous throughput requires incredibly detailed control of each of the 5,000 advanced robots that place the optical fibers in the DESI instrument, ensuring their placement accuracy is within 10 microns. “Ten microns is very small,” Honshed said. “It’s less than the thickness of a human hair. And you have to put in each robot to collect light from galaxies that are billions of light years away. Every time I think about this system I wonder how we can achieve it? DESI’s success as a tool is something to be proud of.”
Seeing the true colors of dark energy
this level the health It is necessary to achieve the primary research mission: to collect detailed images of the color spectrum of millions of galaxies across more than a third of the entire sky. By dividing the light from each galaxy into their color spectrum, DESI can quantify the redshift of the light — stretched toward the red end of the spectrum by the expansion of the universe over the billions of years it has traveled before reaching Earth. It is these redshifts that make DESI see the depth of the sky.
The greater the redshift in a galaxy’s spectrum in general, the further away it is from it. With a 3D map of the universe in hand, physicists can map galaxy clusters and giant clusters. These structures carry echoes of their initial formation, when they were just ripples in the world of childhood. By triggering these echoes, physicists can use DESI data to determine the expansion history of the universe.
The new quasar discovered by DESI gives a glimpse of the universe as it was nearly 13 billion years ago, less than a billion years after the Big Bang. This is the farthest DESI quasar discovered to date, among a selection of extremely high redshift DESI quasars. The background shows this quasar and its surroundings in the old DESI photogrammetry questionnaires. Credit: Jenny Yang, Steward Observatory/University of Arizona
Our scientific goal is to measure the wave signature in plasmaDude said. “It’s amazing that we can actually detect the effect of these waves after billions of years and so quickly in our research.”
Understanding the history of expansion is crucial, as the fate of the entire universe is at stake. Today, about 70% of the universe’s content is dark energy, a mysterious form of energy that accelerates the expansion of the universe. As the universe expands, more dark energy appears, accelerating the expansion further, in a cycle that pushes some of the dark energy in the universe upward. Will dark energy eventually determine the fate of the universe: will it expand forever? Will he collapse in on himself again, in the big explosion back? Or will it be torn? Answering these questions means learning more about how dark energy behaved in the past – and that’s exactly what DESI was designed for. By comparing the history of expansion to the history of growth, cosmologists can see if Einstein’s theory of general relativity holds up over these enormous stretches of space and time.
Black holes and glowing galaxies
But understanding the fate of the universe will have to wait until DESI completes more of its research. Meanwhile, DESI is already advancing our understanding of the distant past, more than 10 billion years ago, when galaxies were still young.
“It’s really amazing,” said Ragadeepika Pucha, a University of Arizona graduate student in astronomy who works at DESI. “DESI will tell us more about the physics of galaxy formation and evolution.”
Bucha and colleagues use DESI data to understand the behavior of medium-mass black holes in small galaxies. Supermassive black holes are believed to inhabit the cores of nearly all large galaxies, such as our own. Milky Way. But if small galaxies always have (smaller) black holes in their cores. Black holes are almost impossible to find on their own – but if they attract enough material, they will become easier to detect. When gas, dust and other materials fall into it Black hole As it warms (to temperatures above the star’s core) on its way inland, an active galactic nucleus (AGN) forms. In large galaxies, active galactic nuclei are among the brightest in the known universe. But in smaller galaxies, AGNs can be fainter and hard to distinguish from newborn stars. Spectra captured by DESI could help solve this problem – and how far they spread across the sky will provide more information about the cores of young galaxies than ever before. These cores, in turn, will give scientists clues to how AGNs formed in the early universe.
Quasars – a variety of bright galaxies – are among the brightest and most distant objects. “I like to think of them as lampposts, given the history of the universe,” said Victoria Fawcett, a graduate student in astronomy at Durham University in the UK. Quasars are excellent probes of the early universe because of their sheer power. DESI data will go back 11 billion years.
Fawcett and his colleagues used DESI data to understand the evolution of quasars themselves. Quasars are thought to begin surrounded by an envelope of dust, which reddens the light they emit, like the sun through fog. As they age, they expel this dust and become bluer. But this theory has been difficult to test, due to the paucity of data on red quasars. DESI changes that, as more quasars have been found than any previous survey, with 2.4 million quasars expected in the final survey data.
“DESI is really great because it picks up the fainter and redder things,” Fawcett said. She adds that this allows scientists to test ideas about the evolution of quasars that could not be tested before. And this is not just limited to quasars. “We found a very large number of exotic systems, including large samples of rare things that we could not study in detail before,” Fawcett said.
There is more to come DESI. The survey has now classified more than 7.5 million galaxies and is adding more at a rate of over one million per month. In November 2021 alone, DESI classified the redshifts of 2.5 million galaxies. By the end of its work in 2026, DESI is expected to have more than 35 million galaxies in its catalog, allowing for a wide range of research in cosmology and astrophysics.
“All of this data is out there and it is just waiting to be analyzed,” Bucha said. “And then we’ll find a lot of amazing things about galaxies. To me, that’s exciting.”
DESI is supported by the Department of Energy’s Office of Science and the National Center for Scientific Computing for Energy Research, a user facility of the Department of Energy’s Office of Science. Additional support for DESI is provided by the US National Science Foundation, the UK Science and Technology Facilities Council, the Gordon and Betty Moore Foundation, the Heising-Simons Foundation, the French Commission for Alternative and Atomic Energy (CEA), the National Science and Technology Council of Mexico, the Spanish Ministry of Economy DESI member institutions.
The DESI Collaboration has the honor to allow him to conduct scientific research on Mount Iolkam Du’ag (Kit’s Peak), a mountain of particular interest to the nation of Tohono O’odham.
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