From Sky & Telescope: “Galaxies Show Order in Chaotic Young Universe”

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Sky & Telescope

January 15, 2018
Monica Young

New observations of galaxies in a universe just 800 million years old show that they’ve already settled into rotating disks. They must have evolved quickly to display such surprising maturity.

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Data visualization of the the velocity gradient across the two surprisingly evolved young galaxies.
Hubble (NASA/ESA), ALMA (ESO/NAOJ/NRAO), P. Oesch (University of Geneva) and R. Smit (University of Cambridge).

NASA/ESA Hubble Telescope

ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres

Our cosmos was a messy youngster. Hotter and denser than the universe we live in now, it was home to turbulent gas flinging about under the influence of gravity. Theorists think the earliest galaxies built up gradually, first clump by clump, then by mergers with other galaxies.

Astronomers expected that most galaxies living among this early chaos would be turbulent masses themselves. But new observations have revealed two surprisingly mature galaxies when the universe was only 800 million years old. Renske Smit (University of Cambridge, UK) and colleagues report in the January 11th Nature that these two galaxies have already settled into rotating disks, suggesting they evolved rapidly right after they were born.

Smit and colleagues first found the two galaxies in deep Spitzer Space Telescope images,

NASA/Spitzer Infrared Telescope

then followed up using the Atacama Large Millimeter/submillimeter Array (ALMA), a network of radio dishes high in the Atacama Desert in Chile. ALMA’s incredible resolution enabled the astronomers to measure radiation from ionized carbon — an element associated with forming stars — across the face of these diminutive galaxies.

Consider for a moment: These galaxies are a fifth the size of the Milky Way, and they’re incredibly far away — their light has traveled 13 billion years to Earth. Even in images taken by the eagle-eyed Hubble Space Telescope, such galaxies appear as small red dots.

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Distant Galaxies in the Hubble Ultra Deep Field
This Hubble Space Telescope image shows 28 of the more than 500 young galaxies that existed when the universe was less than 1 billion years old. The galaxies were uncovered in a study of two of the most distant surveys of the cosmos, the Hubble Ultra Deep Field (HUDF), completed in 2004, and the Great Observatories Origins Deep Survey (GOODS), made in 2003.

Just a few years ago, astronomers had not spotted any galaxies that existed significantly less than 1 billion years after the Big Bang. The galaxies spied in the HUDF and GOODS surveys are blue galaxies brimming with star birth.

The large image at left shows the Hubble Ultra Deep Field, taken by the Hubble telescope. The numbers next to the small boxes correspond to close-up views of 28 of the newly found galaxies at right. The galaxies in the postage-stamp size images appear red because of their tremendous distance from Earth. The blue light from their young stars took nearly 13 billion years to arrive at Earth. During the journey, the blue light was shifted to red light due to the expansion of space.

Yet astronomers are now able to point an array of radio dishes to not only spot the galaxies themselves but also capture features within them down to a couple thousand light-years across.

They Grow Up So Fast

The ALMA observations revealed that these two galaxies aren’t the turbulent free-for-all that astronomers expect for most galaxies in this early time period. Their rotating disks aren’t quite like the Milky Way’s, as spiral arms take time to form. Instead, they look more like the fluffy disk galaxies typically seen at so-called cosmic noon, the universe’s adolescent period of star formation and galaxy growth. That implies rapid evolution, as cosmic noon occurred more than 2 billion years after these two galaxies existed.

Simulations had predicted that it’s possible for some galaxies to evolve more quickly than their peers, notes Nicolas LaPorte (University College London), but it had never been observed before. “This paper represents a great leap forward in the study of the first galaxies,” he says.

Smit says that these two galaxies seem to stand out from their cohort, which makes sense given their quick growth: Among other things, they’re forming tens of Suns’ worth of stars every year, more than is typical for their time period. Smit is already planning additional observations to see just how different these galaxies are from their peers.

See the full article here .

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Sky & Telescope magazine, founded in 1941 by Charles A. Federer Jr. and Helen Spence Federer, has the largest, most experienced staff of any astronomy magazine in the world. Its editors are virtually all amateur or professional astronomers, and every one has built a telescope, written a book, done original research, developed a new product, or otherwise distinguished him or herself.

Sky & Telescope magazine, now in its eighth decade, came about because of some happy accidents. Its earliest known ancestor was a four-page bulletin called The Amateur Astronomer, which was begun in 1929 by the Amateur Astronomers Association in New York City. Then, in 1935, the American Museum of Natural History opened its Hayden Planetarium and began to issue a monthly bulletin that became a full-size magazine called The Sky within a year. Under the editorship of Hans Christian Adamson, The Sky featured large illustrations and articles from astronomers all over the globe. It immediately absorbed The Amateur Astronomer.

Despite initial success, by 1939 the planetarium found itself unable to continue financial support of The Sky. Charles A. Federer, who would become the dominant force behind Sky & Telescope, was then working as a lecturer at the planetarium. He was asked to take over publishing The Sky. Federer agreed and started an independent publishing corporation in New York.

“Our first issue came out in January 1940,” he noted. “We dropped from 32 to 24 pages, used cheaper quality paper…but editorially we further defined the departments and tried to squeeze as much information as possible between the covers.” Federer was The Sky’s editor, and his wife, Helen, served as managing editor. In that January 1940 issue, they stated their goal: “We shall try to make the magazine meet the needs of amateur astronomy, so that amateur astronomers will come to regard it as essential to their pursuit, and professionals to consider it a worthwhile medium in which to bring their work before the public.”