̽��ֱ�� of Cambridge - Nicolas Laporte

Slow spin of early galaxy observed for the first time

sc604 — Fri, 01 Jul 2022 02:45:18 +0000

For the study, published in ̽��ֱ��Astrophysical Journal Letters, an international team of researchers analysed data from a galaxy known as MACS1149-JD1 (JD1), obtained from observations by the Atacama Large Millimeter/submillimeter Array (ALMA), an assembly of radio telescopes in Chile.

̽��ֱ��galaxy is so far away that its light comes to us from a time when the Universe was only 550 million years old – 4% of its present age.

̽��ֱ��researchers, led by Tsuyoshi Tokuoka of Waseda ̽��ֱ��, found subtle variations in the wavelengths of the light indicating that parts of the galaxy were moving away from us while other parts were moving towards us. From these variations, they concluded that the galaxy was disc-shaped and rotating at a speed of 50 kilometres a second. By contrast, the Milky Way, at the Sun’s position, rotates with a speed of 220 kilometres per second today.

From the size of the galaxy and the speed of its rotation, the researchers were able to infer its mass, which in turn enabled them to confirm that it was likely 300 million years old and therefore formed about 250 million years after the Big Bang.

“This is by far the furthest back in time we have been able to detect a galaxy’s spin,” said co-author Professor Richard Ellis from ̽��ֱ�� College London (UCL). “It allows us to chart the development of rotating galaxies over 96% of cosmic history – rotations that started slowly initially, but became more rapid as the Universe aged.

“These measurements support our earlier findings that this galaxy is well-established and likely formed about 250 million years after the Big Bang. On a cosmic time scale, we see it rotating not long after stars first lit up the Universe.”

“Our findings shed light on how galaxies evolved in the early Universe,” said co-author Dr Nicolas Laporte, from Cambridge’s Kavli Institute for Cosmology. “We see that, 300 million years after massive molecular clouds condensed and fused into stars, a galactic disk has developed and the galaxy has acquired a shape and rotation.”

“Determining whether distant galaxies are rotating is very challenging because they only appear as tiny dots in the sky,” said co-author Professor Akio K. Inoue, from Waseda ̽��ֱ��, Tokyo “Our new findings came thanks to two months of observations and the high resolution achieved by combining the 54 radio telescopes of the ALMA observatory.”

̽��ֱ��further away a galaxy is from Earth, the faster it appears to move away from us. As objects moving away emit light shifted towards longer wavelengths ('redshifted'), this means we can calculate their distance, and in turn their age, from the extent of redshift.

Past studies have found JD1’s redshift to be 9.1, meaning what we see is from when the Universe was 550 million years old. In the latest study, the team picked out variations in the redshift across the galaxy, indicating differences in the speed at which the galaxy was moving away from us, meaning that, relatively speaking, one side was moving away while the other side was moving closer.

From the new observations, the team concluded that JD1 was only 3,000 light years across (by comparison, the Milky Way is 100,000 light years across) and that its total mass was equivalent to 1-2 billion times the mass of the Sun.

This mass is consistent with the galaxy being about 300 million years old, with most of the mass coming from mature stars that formed close to the start of the galaxy’s life.

̽��ֱ��finding supports earlier evidence from the same researchers, who came up with the same age estimate for JD1 in a paper published last year, using a different technique based on the brightness of light at various frequencies. They determined the age of six galaxies including JD1, concluding that cosmic dawn – the moment stars first lit up the Universe – occurred 200 to 300 million years after the Big Bang.

̽��ֱ��research was supported by MEXT in Japan, the Japan Society for the Promotion of Science, the European Research Council under the EU Horizon 2020 research and innovation programme, and the Kavli Foundation.

Reference:
Tsuyoshi Tokuoka et al. ‘Possible Systematic Rotation in the Mature Stellar Population of a z = 9.1 Galaxy.’ ̽��ֱ��Astrophysical Journal Letters (2022). DOI:

One of the most distant known galaxies, observed in the very earliest years of the Universe, appears to be rotating at less than a quarter of the speed of the Milky Way today, according to a new study involving ̽��ֱ�� of Cambridge researchers.

ESO/C Malin

̽��ֱ��Atacama Large Millimeter/submillimeter Array (ALMA) by night

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

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Astronomers pinpoint when cosmic dawn occurred

sc604 — Thu, 24 Jun 2021 13:00:00 +0000

̽��ֱ��study, published in the Monthly Notices of the Royal Astronomical Society, suggests that the NASA James Webb Space Telescope (JWST), scheduled to launch in November 2021, will be sensitive enough to observe the birth of galaxies directly.

̽��ֱ��UK-led research team examined six of the most distant galaxies currently known, whose light has taken most of the universe’s lifetime to reach us. They found that the distance of these galaxies away from Earth corresponded to a ‘look back’ time of more than 13 billion years ago, when the universe was only 550 million years old.

Analysing images from the Hubble and Spitzer Space Telescopes, the researchers calculated the age of these galaxies as ranging from 200 to 300 million years, allowing an estimate of when their stars first formed.

"Theorists speculate that the universe was a dark place for the first few hundred million years, before the first stars and galaxies formed," said lead author Dr Nicolas Laporte from Cambridge's Institute of Astronomy. "Witnessing the moment when the universe was first bathed in starlight is a major quest in astronomy.

"Our observations indicate that cosmic dawn occurred between 250 and 350 million years after the beginning of the universe, and, at the time of their formation, galaxies such as the ones we studied would have been sufficiently luminous to be seen with the James Webb Space Telescope."

̽��ֱ��researchers analysed starlight from the galaxies as recorded by the Hubble and Spitzer Space Telescopes, examining a marker in their energy distribution indicative of the presence of atomic hydrogen in their stellar atmospheres. This provides an estimate of the age of the stars they contain.

This hydrogen signature increases in strength as the stellar population ages but diminishes when the galaxy is older than a billion years. ̽��ֱ��age-dependence arise because the more massive stars that contribute to this signal burn their nuclear fuel more rapidly and therefore die first.

"This age indicator is used to date stars in our own neighbourhood in the Milky Way but it can also be used to date extremely remote galaxies, seen at a very early period of the universe," said co-author Dr Romain Meyer from UCL and the Max Planck Institute for Astronomy. "Using this indicator we can infer that, even at these early times, our galaxies are between 200 and 300 million years old."

In analysing the Hubble and Spitzer data, the researchers needed to estimate the 'redshift' of each galaxy, which indicates their cosmological distance and hence the look-back time at which they are being observed. To achieve this, they undertook spectroscopic measurements using the full armoury of ground-based telescopes - the Chilean Atacama Large Millimetre Array (ALMA), the European Very Large Telescope, the twin Keck telescopes in Hawai'i, and Gemini-South telescope.

These measurements enabled the team to confirm that looking at these galaxies corresponded to looking back to a time when the universe was 550 million years old.

"Over the last decade, astronomers have pushed back the frontiers of what we can observe to a time when the universe was only 4% of its present age," said co-author Professor Richard Ellis from UCL. "However, due to the limited transparency of Earth's atmosphere and capabilities of the Hubble and Spitzer Space Telescopes, we have reached our limit.

"We now eagerly await the launch of the James Webb Space Telescope, which we believe has the capability to directly witness cosmic dawn. ̽��ֱ��quest to see this important moment in the universe's history has been a holy grail in astronomy for decades. Since we are made of material processed in stars, this is in one sense the search for our own origins."

̽��ֱ��new study involved astronomers from the ̽��ֱ�� of California-Santa Cruz, the ̽��ֱ�� of California, and the ̽��ֱ�� of Texas.

̽��ֱ��researchers received support from the Kavli Foundation, the European Research Council, the National Aeronautics and Space Administration (NASA), and the National Science Foundation (NSF) in the United States.

̽��ֱ��NASA-led James Webb Space Telescope, the successor to the Hubble observatory, is scheduled to be launched into space in November. It will be the premier observatory over the next decade, serving thousands of astronomers worldwide.

Reference:
N Laporte et al. 'Probing Cosmic Dawn: Ages and Star Formation Histories of Candidate z ≥ 9 Galaxies.' ̽��ֱ��Monthly Notices of the Royal Astronomical Society (2021).

Adapted from a UCL press release.

Cosmic dawn, when stars formed for the first time, occurred 250 million to 350 million years after the beginning of the universe, according to a new study led by researchers from the ̽��ֱ�� of Cambridge and ̽��ֱ�� College London (UCL).

Witnessing the moment when the universe was first bathed in starlight is a major quest in astronomy

Nicolas Laporte

Dr Harley Katz, Beecroft Fellow, Department of Physics, ̽��ֱ�� of Oxford

̽��ֱ��formation and evolution of the first stars and galaxies in a virtual universe similar to our own

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