Science and Exploration

W. M. Keck Observatory Achieves First Light With Keck Cosmic Reionization Mapper

By Keith Cowing
Press Release
W. M. Keck Observatory
June 13, 2023
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W. M. Keck Observatory Achieves First Light With Keck Cosmic Reionization Mapper
LCRM’s First light image of the Turtle Nebula Credit: C. Martin, Caltech/Keck Observatory/NASA/STScI
W. M. Keck Observatory

W. M. Keck Observatory is pleased to announce its newest instrument, the Keck Cosmic Reionization Mapper (KCRM), has successfully achieved “first light,” marking its first time ‘seeing’ the universe from Maunakea on Hawaiʻi Island. On Sunday, June 4, KCRM team members from Keck Observatory and Caltech captured a first-light image of the Turtle Nebula, or NGC 6210, located about 6,600 light-years away in the Hercules constellation.

“Because of the pristine view from Maunakea and KCRM’s remarkable depth of vision into the early universe, we have a new way for our galactic ancestors to reveal profound knowledge about our cosmic lineage and heritage,” says Rich Matsuda, interim director of Keck Observatory.

KCRM is designed to investigate the mysteries surrounding the era after the Big Bang when the cosmos was a toddler and light from the first stars transitioned the universe from darkness to light. This period of time is called the Epoch of Reionization (hence, KCRM’s name), when the first stars and galaxies began to form, emitting radiation powerful enough to burn through the dark, dense fog of cool hydrogen gas that filled the universe.

“Our understanding of the formation of the first galaxies and how they quickly evolved is incomplete,” says John OʻMeara, chief scientist at Keck Observatory. “With KCRM, we’ll be able to take direct measurements of the first galaxies that are at the edge of emergence from the Epoch of Reionization, just as they’ve started to mature after being born in the early chapters of the universe’s history.”

The Keck Cosmic Web Imager (KCWI) and its recently installed partner, the Keck Cosmic Reionization Mapper (KCRM), have obtained a spectrographic image of the Turtle Nebula, or NGC 6210, a complex planetary nebula created by a hot, dying star (that may in fact be a triple star system) that has blown off its envelope. The star is exciting the nebula gas with radiation from its recently unveiled hot inner core. Panel “a” shows a Hubble Space Telescope image of the nebula, and panel “b” shows the KCWI+KCRM image in three emission lines, coded by colors (blue, green, red) as seen in panels “d,” “e,” and “f.” Panel “c” shows the outer portion of the nebula captured by KCWI/KCRM, including two extended, faint filaments (“arms” of the turtle). The spectrum of the nebula is shown at right, extending over the full 350 to 1,080 nanometer optical wavelength range of the instruments. More than 80 individual spectral lines from many elements in the periodic table can be seen. Credit: C. Martin, Caltech/Keck Observatory/NASA/STScI

KCRM is a major upgrade to the Keck Cosmic Web Imager (KCWI), which was commissioned in 2017; together, they can take images in wavelengths of light that our eyes can see, with KCWI covering the blue side of the visible spectrum (wavelengths ranging from 350 to 560 nanometers) and KCRM covering the red side (wavelengths ranging from 560 to 1080 nanometers). Having both a blue arm and a red arm gives the combined instrument highly-advanced viewing power to not only travel back in time some 10 to 12 billion years ago and observe objects during the Epoch of Reionization, but also capture images of the vast strands of gas that stretch out across the universe connecting galaxies, called the cosmic web.

“I envisioned this instrument as a two-armed imaging spectrograph back in 2007, based on our Palomar Cosmic Web Imager but it was a long road to get the funding so we split the instrument into two halves,” says Christopher Martin, the instrument’s principal investigator and a professor of physics at Caltech. “KCWI was already doing phenomenal science with one arm tied behind its back, so now it’s off to the races! It is fitting that our first-light image shows two ‘arms’ of the Turtle Nebula! We would not have made it without the work of our fantastic instrument team, and support from Caltech, the Keck Observatory, the National Science Foundation, and a generous anonymous donor.”

The first-light image of NGC 6210 is a testament to the power of KCRM and KCWI; Martin says they captured the turtle-shaped nebula in less than a minute of observation and with such detail, the stubby ‘arms’ can be seen protruding from its ‘shell.’

In addition to studying the first galaxies and the cosmic web, both instruments can also observe gas jets around young stars, winds of dead stars, supermassive black holes, dark matter, and more.

“I’m excited to finally study galaxies in enough detail to understand why gas flows out,” says Rosalie McGurk, staff astronomer and KCRM lead at Keck Observatory. “KCRM will take my studies of merging galaxies, their supermassive black holes, and their outflowing gas to new heights. Studying them in multiple wavelength ranges simultaneously will help us determine whether energy from active black holes or star formation is pushing the gas out of the galaxies.”

With its KCRM upgrade now complete thanks to engineering teams from Caltech, UCO/Lick Observatory, and Keck Observatory, KCWI will be available again for science use starting in August.

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