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DESI Spectrograph on the Kitt Peak 4m Sees First Light: UArizona has Played a Significant Role

The new DESI spectrograph on the Mayall 4m telescope on Kitt Peak has seen first light. You can read the UArizona UANews press release HERE, and the Sky & Telescope article HERE.

Quoting from the UArizona press release: A new instrument mounted atop a telescope in Arizona aimed its robotic array of 5,000 fiber-optic “eyes” at the night sky to capture the first images of its unique view of galaxy light. It was the first test of the Dark Energy Spectroscopic Instrument, or  DESI, which is designed to explore the mystery of dark energy that makes up about 68% of the universe and is speeding up its expansion.

"DESI will give us a three-dimensional map of galaxies, quasars and intergalactic gas over a very large part of the universe," said Xiaohui Fan, a Regents Professor of astronomy at Steward Observatory. "By looking at that map, we can see how the structure of the universe has changed with cosmic time, and that gives us an idea of how fast the universe is expanding at any given time."

Fan explained that DESI can map 20 times more quasars and galaxies than previous surveys, which were limited to a fairly small number of snapshots over the course of the history of the cosmos.

"This survey will cover its history almost continuously, and that will allow us to measure the effect of dark energy with much better precision than before," he said.

UArizona scientists helped lay the groundwork for the DESI project by conducting an imaging survey that was used to identify the targets on which DESI will train its robotic eyes. The survey was completed using more than 360 nights of observing time on the university's Bok Telescope, which is located next to the Mayall Telescope on Kitt Peak.

The DESI collaboration has participation from nearly 500 researchers at 75 institutions in 13 countries, including more than a dozen UArizona students, postdoctoral fellows and faculty members.

Each of the ten planned spectrographs is equipped with three cameras, one each for ultraviolet, visible and infrared wavelengths.The UV channel for each spectrograph contains a thinned, UV/Blue-sensitive, 4096x4096 CCD produced at  UArizona's Imaging Technology Lab. ITL is directed by Dr. Michael Lesser, a Steward Observatory faculty member.

The spectra obtained with DESI will inform science that goes beyond the study of dark energy, according to Steward Observatory Director Buell Jannuzi. In addition to probing quasars and galaxies, DESI will take spectra of stars and help answer questions about the nature of dark matter, which is invisible but thought to far surpass the amount of visible matter in the universe. In addition, the survey will help scientists to better understand the evolution of galaxies and quasars over time, all questions that UArizona researchers are working on, he said.

"With DESI we are creating a legacy dataset that will support all kinds of astrophysics in the future," Jannuzi said.

(The figure on the front page of this article shows the ten robot positioners mounted at the top of the prime focus of the Mayall 4m telescope (photo courtesy NOAO). We also thank Daniel Stolte.)

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