Primordial Galaxy Discovered, First of Its Kind

MACS1423-z7p64 galaxy
Graphic illustration of how MACS1423-z7p64 was detected via gravitational lensing with NASA’s Hubble Space Telescope and confirmed by W. M. Keck Observatory’s MOSFIRE. Credit: NASA/W. M. Keck Observatory/A. Hoag/M. Bradac
W. M. Keck Observatory press release

Seven years of meticulous observing have resulted in a cosmic discovery that comes from an era dating back 13.1 billion years, giving scientists a detailed glimpse of what may have happened just after the Big Bang.

Using the world-class W. M. Keck Observatory on Maunakea, Hawaii, an international team of astronomers from the United States, Australia, and Europe has confirmed the existence of one of the most distant galaxies in the universe.

To characterize the faint galaxy, the discovery team, led by Austin Hoag, a University of California, Davis physics graduate student, used MOSFIRE, the most in-demand instrument on the 10-meter Keck I telescope.

What makes this galaxy extraordinary is that it is ordinary. It is thought to be a common galaxy at that distance and age of the universe. However, such galaxies would normally be too faint to detect. The astronomers used a method called gravitational lensing to magnify the galaxy so they could study it.

“Most objects that we’ve seen at that distance are extremely bright, and probably rare compared to other galaxies,” said Hoag. “We think this galaxy is much more representative of other galaxies of its time.”

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Ancient Dead Galaxy Sets New Record

W. M. Keck Observatory press release

Galaxy ZF-COSMOS-20115
Artist’s impression of galaxy ZF-COSMOS-20115. The galaxy has likely blown off all the gas that caused its rapid star formation and mass growth, and rapidly turned into a compact red galaxy. Credit: CREDIT: Leonard Doublet/Swinburne University of Technology.
An international team of astronomers has, for the first time, spotted a massive, inactive galaxy from a time when the Universe was only 1.65 billion years old. This rare discovery, made using the world-class W. M. Keck Observatory on Maunakea, Hawaii, could change the way scientists think about the evolution of galaxies.

This research publishes today in the journal Nature, with Professor Karl Glazebrook, director of Swinburne’s Centre for Astrophysics and Supercomputing , as the lead author. To characterize the faint galaxy, the discovery team used MOSFIRE, the most in-demand instrument on the 10-meter Keck I telescope.

“This observation was only possible due to the extreme sensitivity of the new MOSFIRE spectrograph,” said Glazebrook. “It is the absolute best in the world for faint near-IR spectra by a wide margin. Our team is indebted to the accomplishment of Chuck Steidel, Ian McClean, and all the Keck Observatory staff for building and delivering this remarkable instrument.”

Astronomers expect most galaxies from this epoch to be low-mass minnows, busily forming stars. However, this galaxy is ‘a monster’ and inactive.

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Milky Way Gallery

Astronomers Measure Universe Expansion, Get Hints of ‘New Physics’

W. M. Keck Observatory press release

Astronomers have just made a new measurement of the Hubble constant, the rate at which the universe is expanding, and it doesn’t quite line up with a different estimate of the same number. That discrepancy could hint at “new physics” beyond the standard model of cosmology, according to the team, which includes physicists from the University of California, Davis, that made the observation.

Lensed Quasar HE0435-1223
The image of this quasar is split into four by a massive galaxy acting as a gravitational lens. Image credit: Sherry Suyu, European Space Agency/Hubble Space Telescope/NASA
The Hubble constant allows astronomers to measure the scale and age of the universe and measure the distance to the most remote objects we can see, said Chris Fassnacht, a physics professor at UC Davis and a member of the international H0LiCOW (H0 Lenses in COSMOGRAIL’s Wellspring) collaboration, which carried out the work.

Led by Sherry Suyu at the Max Planck Institute for Astrophysics in Germany, the H0LICOW team used the NASA/ESA Hubble Space Telescope and other space- and Earth-based telescopes, including the Keck telescopes in Hawaii, to observe three galaxies and arrive at an independent measurement of the Hubble constant. Eduard Rusu, a postdoctoral researcher at UC Davis, is first author on one of five papers describing the work, due to be published in the Monthly Notices of the Royal Astronomical Society.

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Universe Gallery

Scientists Discover Massive Galaxy Made of 99.99 Percent Dark Matter

W. M. Keck Observatory press release

Using the world’s most powerful telescopes, an international team of astronomers has discovered a massive galaxy that consists almost entirely of Dark Matter. Using the W. M. Keck Observatory and the Gemini North telescope – both on Maunakea, Hawaii – the team found a galaxy whose mass is almost entirely Dark Matter. The findings are being published in The Astrophysical Journal Letters today.

Dragonfly 44
The dark galaxy Dragonfly 44. Credit: Pieter Van Dokkum, Roberto Abraham Gemini, Sloan Digital Sky Survey
Even though it is relatively nearby, the galaxy, named Dragonfly 44, had been missed by astronomers for decades because it is very dim. It was discovered just last year when the Dragonfly Telephoto Array observed a region of the sky in the constellation Coma. Upon further scrutiny, the team realized the galaxy had to have more than meets the eye: it has so few stars that it quickly would be ripped apart unless something was holding it together.

To determine the amount of Dark Matter in Dragonfly 44, astronomers used the DEIMOS instrument installed on Keck II to measure the velocities of stars for 33.5 hours over a period of six nights so they could determine the galaxy’s mass. The team then used the Gemini Multi-Object Spectrograph (GMOS) on the 8-meter Gemini North telescope on Maunakea in Hawaii to reveal a halo of spherical clusters of stars around the galaxy’s core, similar to the halo that surrounds our Milky Way Galaxy.

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Cosmic Neighbors Inhibit Star Formation, Even in the Early-Universe

W. M. Keck Observatory press release

Galaxy cluster MACS J0416
Massive galaxy cluster MACS J0416 seen in X-rays (blue), visible light (red, green, and blue), and radio light (pink). Credit: NASA, CXC, SAO, G.Ogrean, STSCI, NRAO, AUI, NSF
The international University of California, Riverside-led SpARCS collaboration has discovered four of the most distant clusters of galaxies ever found, as they appeared when the Universe was only four billion years old. Clusters are rare regions of the Universe consisting of hundreds of galaxies containing trillions of stars, as well as hot gas and mysterious Dark Matter. Spectroscopic observations from the W. M. Keck Observatory on Maunakea, Hawaii and the Very Large Telescope in Chile confirmed the four candidates to be massive clusters. This sample is now providing the best measurement yet of when and how fast galaxy clusters stop forming stars in the early Universe.

“We looked at how the properties of galaxies in these clusters differed from galaxies found in more typical environments with fewer close neighbors,” said lead author Julie Nantais, an assistant professor at the Andres Bello University in Chile. “It has long been known that when a galaxy falls into a cluster, interactions with other cluster galaxies and with hot gas accelerate the shut off of its star formation relative to that of a similar galaxy in the field, in a process known as environmental quenching. The SpARCS team have developed new techniques using Spitzer Space Telescope infrared observations to identify hundreds of previously-undiscovered clusters of galaxies in the distant Universe.”

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UCLA Astronomers Use Keck Observatory to Look Back 12 Billion Years and Measure Oxygen

W. M. Keck Observatory press release

UCLA astronomers have used the W. M. Keck Observatory on Maunakea, Hawaii to make the first accurate measurement of the abundance of oxygen in a distant galaxy. Oxygen, the third-most abundant chemical element in the Universe, is created inside stars and released into interstellar gas when stars die. Quantifying the amount of oxygen is key to understanding how matter cycles in and out of galaxies. This research is published online in the Astrophysical Journal Letters.

COSMOS-1908
Galaxy COSMOS-1908 is in the center of this Hubble Space Telescope image, indicated by the arrow. Nearly everything in the image is a galaxy.
Credit: Ryan Sandres and the CANDELS Team
“This is by far the most distant galaxy for which the oxygen abundance has actually been measured,” said Alice Shapley, a UCLA professor of astronomy, and co-author of the study. “We’re looking back in time at this galaxy as it appeared 12 billion years ago.”

Knowing the abundance of oxygen in the galaxy called COSMOS-1908 is an important stepping stone toward allowing astronomers to better understand the population of faint, distant galaxies observed when the Universe was only a few billion years old, Shapley said.

COSMOS-1908 contains approximately one billion stars. In contrast, the Milky Way contains approximately 100 billion stars. Furthermore, COSMOS-1908 contains approximately only 20 percent the abundance of oxygen that is observed in the Sun.

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Faintest Early-Universe Galaxy Ever, Detected and Confirmed

W. M. Keck Observatory press release

An international team of scientists has detected and confirmed the faintest early-Universe galaxy ever using the W. M. Keck Observatory on the summit on Maunakea, Hawaii. In addition to using the world’s most powerful telescope, the team relied on gravitational lensing to see the incredibly faint object born just after the Big Bang. The results are being published in The Astrophysical Journal Letters today.

MACS2129.4-0741
Color image of the cluster taken with Hubble Space Telescope (images in three different filters were combined to make an RGB image). Credit: Bradac/HST/W. M. Keck Observatory
The team detected the galaxy as it was 13 billion years ago, or when the Universe was a toddler on a cosmic time scale.

The detection was made using the DEIMOS instrument fitted on the ten-meter Keck II telescope, and was made possible through a phenomenon predicted by Einstein in which an object is magnified by the gravity of another object that is between it and the viewer. In this case, the detected galaxy was behind the galaxy cluster MACS2129.4-0741, which is massive enough to create three different images of the object.

“Keck Observatory’s telescopes are simply the best in the world for this work,” said Marusa Bradac, a proefssor at University of California, Davis who led the team. “Their power, paired with the gravitational force of a massive cluster of galaxies, allows us to truly see where no human has seen before.”

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