The Universe’s Secret Harvest: ALMA Sheds Light on “the Cosmic Grapes”

An artist’s impression of the “Cosmic Grapes” galaxy, composed of at least 15 massive star forming clumps—far more than current theoretical models predict could exist within a single rotating disk at this early time. Image credit NSF/AUI/NSF NRAO/B.Saxton.Credit: NSF/AUI/NSF NRAO/B. Saxton. Hi-Res File

The Cosmic Grapes initially appeared in past HST data as a typical galaxy with a smooth stellar disk (left). However, deep, high-resolution follow-up observations by JWST (middle) and ALMA (right) revealed that it actually consists of numerous compact stellar clumps embedded within a smooth, rotating gas disk. The red and blue colors in the right panel represent redshifted and blueshifted gas motions, respectively, tracing the rotation of the disk. Credit: NSF/AUI/NSF NRAO/B. Saxton. Hi-Res File

The Cosmic Grapes initially appeared in past HST data as a typical galaxy with a smooth stellar disk (left). However, deep, high-resolution follow-up observations by JWST (middle) and ALMA (right) revealed that it actually consists of numerous compact stellar clumps embedded within a smooth, rotating gas disk. The red and blue colors in the right panel represent redshifted and blueshifted gas motions, respectively, tracing the rotation of the disk. Credit: Data images noted from specific instruments, assemble by NSF/AUI/NSF NRAO/B.Saxton. Hi-Res File

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ALMA and JWST observations unveil unexpected details of rapid growth in a faint, newborn “grape-like” galaxy, similar to galaxies in the early universe following the Big Bang

Astronomers have discovered a remarkably clumpy rotating galaxy that existed just 900 million years after the Big Bang, shedding new light on how galaxies grew and evolved in the early universe. Nicknamed the “Cosmic Grapes,” the galaxy appears to be composed of at least 15 massive star-forming clumps—far more than current theoretical models predict could exist within a single rotating disk at this early time.

The discovery was made possible by an extraordinary combination of observations from the Atacama Large Millimeter/submillimeter Array (ALMA) and the James Webb Space Telescope (JWST), all focused on a single galaxy that happened to be perfectly magnified by a foreground galaxy cluster through gravitational lensing. In total, more than 100 hours of telescope time were dedicated to this single system, making it one of the most intensively studied galaxies from the early universe.

Although the galaxy had appeared as a smooth, single disk-like object in previous Hubble images, the powerful resolution of ALMA and JWST, enhanced by gravitational lensing, revealed a dramatically different picture: a rotating galaxy teeming with massive clumps, resembling a cluster of grapes. The finding marks the first time astronomers have linked small-scale internal structures and large-scale rotation in a typical galaxy at cosmic dawn, reaching spatial resolutions down to just 10 parsecs (about 30 light-years).

This galaxy does not represent a rare or extreme system. It lies squarely on the “main sequence” of galaxies in terms of its star forming activity, mass, size, chemical composition—meaning it is likely representative of a broader population. If so, many other seemingly smooth galaxies seen by current facilities may actually be made up of similar unseen substructures, hidden by the limits of current resolution.

Because existing simulations fail to reproduce such a large number of clumps in rotating galaxies at early times, this discovery raises key questions about how galaxies form and evolve. It suggests that our understanding of feedback processes and structure formation in young galaxies may need significant revision. The Cosmic Grapes now offer a unique window into the birth and growth of galaxies — and may be just the first of many. Future observations will be key to revealing whether such clumpy structures were common in the universe’s youth.

Source: National Radio Astronomy Observatory (NRAO)/News

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About NRAO

The National Radio Astronomy Observatory (NRAO) is a facility of the U.S. National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

About ALMA

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Southern Observatory (ESO), the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science and Technology Council (NSTC) in Taiwan and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).

ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

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NSF NOIRLab Astronomers Discover the Fastest-Feeding Black Hole in the Early Universe

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Artist’s Impression of Fastest-feeding Black Hole in the Early Universe

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Artist concept of JWST

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Chandra X-Ray Observatory

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Artist’s Impression of Black Hole LID-568

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Artist’s Impression of Early-Universe Dwarf Galaxy

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Videos

PR Video noirlab2427a
Cosmoview Episode 89: NSF NOIRLab Astronomers Discover the Fastest-Feeding Black Hole in the Early Universe

PR Video noirlab2427b
Cosmoview Episodio 88: Astrónomos de NOIRLab descubren el agujero negro más voraz del Universo primitivo

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Observations from JWST and Chandra reveal a low-mass supermassive black hole that appears to be consuming matter at over 40 times the theoretical limit

Using data from NASA's JWST and Chandra X-ray Observatory, a team of U.S. National Science Foundation NOIRLab astronomers have discovered a supermassive black hole at the center of a galaxy just 1.5 billion years after the Big Bang that is consuming matter at a phenomenal rate — over 40 times the theoretical limit. While short lived, this black hole’s ‘feast’ could help astronomers explain how supermassive black holes grew so quickly in the early Universe.

Supermassive black holes exist at the center of most galaxies, and modern telescopes continue to observe them at surprisingly early times in the Universe’s evolution. It’s difficult to understand how these black holes were able to grow so big so rapidly. But with the discovery of a low-mass supermassive black hole feasting on material at an extreme rate, seen just 1.5 billion years after the Big Bang, astronomers now have valuable new insights into the mechanisms of rapidly growing black holes in the early Universe.

LID-568 was discovered by a cross-institutional team of astronomers led by International Gemini Observatory/NSF NOIRLab astronomer Hyewon Suh. They used the James Webb Space Telescope (JWST) to observe a sample of galaxies from the Chandra X-ray Observatory’s COSMOS legacy survey. This population of galaxies is very bright in the X-ray part of the spectrum, but are invisible in the optical and near-infrared. JWST’s unique infrared sensitivity allows it to detect these faint counterpart emissions.

LID-568 stood out within the sample for its intense X-ray emission, but its exact position could not be determined from the X-ray observations alone, raising concerns about properly centering the target in JWST’s field of view. So, rather than using traditional slit spectroscopy, JWST’s instrumentation support scientists suggested that Suh’s team use the integral field spectrograph on JWST’s NIRSpec. This instrument can get a spectrum for each pixel in the instrument’s field of view rather than being limited to a narrow slice.

“Owing to its faint nature, the detection of LID-568 would be impossible without JWST. Using the integral field spectrograph was innovative and necessary for getting our observation,” says Emanuele Farina, International Gemini Observatory/NSF NOIRLab astronomer and co-author of the paper appearing in Nature Astronomy.

JWST’s NIRSpec allowed the team to get a full view of their target and its surrounding region, leading to the unexpected discovery of powerful outflows of gas around the central black hole. The speed and size of these outflows led the team to infer that a substantial fraction of the mass growth of LID-568 may have occurred in a single episode of rapid accretion. “This serendipitous result added a new dimension to our understanding of the system and opened up exciting avenues for investigation,” says Suh.

In a stunning discovery, Suh and her team found that LID-568 appears to be feeding on matter at a rate 40 times its Eddington limit. This limit relates to the maximum luminosity that a black hole can achieve, as well as how fast it can absorb matter, such that its inward gravitational force and outward pressure generated from the heat of the compressed, infalling matter remain in balance. When LID-568’s luminosity was calculated to be so much higher than theoretically possible, the team knew they had something remarkable in their data.

“This black hole is having a feast,” says International Gemini Observatory/NSF NOIRLab astronomer and co-author Julia Scharwächter. “This extreme case shows that a fast-feeding mechanism above the Eddington limit is one of the possible explanations for why we see these very heavy black holes so early in the Universe.”

These results provide new insights into the formation of supermassive black holes from smaller black hole ‘seeds’, which current theories suggest arise either from the death of the Universe’s first stars (light seeds) or the direct collapse of gas clouds (heavy seeds). Until now, these theories lacked observational confirmation. “The discovery of a super-Eddington accreting black hole suggests that a significant portion of mass growth can occur during a single episode of rapid feeding, regardless of whether the black hole originated from a light or heavy seed,” says Suh.

The discovery of LID-568 also shows that it’s possible for a black hole to exceed its Eddington limit, and provides the first opportunity for astronomers to study how this happens. It’s possible that the powerful outflows observed in LID-568 may be acting as a release valve for the excess energy generated by the extreme accretion, preventing the system from becoming too unstable. To further investigate the mechanisms at play, the team is planning follow-up observations with JWST.

Source: NSF’s National Optical-Infrared Astronomy Research Laboratory (NOIRLab)/News

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More information

This research was presented in a paper entitled “A super-Eddington-accreting black hole ~1.5 Gyr after the Big Bang observed with JWST” to appear in Nature Astronomy. DOI: 10.1038/s41550-024-02402-9

The team is composed of Hyewon Suh (International Gemini Observatory/NSF NOIRLab, USA), Julia Scharwächter (International Gemini Observatory/NSF NOIRLab, USA), Emanuele Paolo Farina (International Gemini Observatory/NSF NOIRLab, USA), Federica Loiacono (INAF – Astrophysics and Space Science Observatory, Italy), Giorgio Lanzuisi (INAF – Astrophysics and Space Science Observatory, Italy), Günther Hasinger (Institute of Nuclear and Particle Physics/DESY/German Center for Astrophysics, Germany), Stefano Marchesi (INAF-Astrophysics and Space Science Observatory, Italy), Mar Mezcua (Institute of Space Sciences/Institute of Spatial Studies of Catalonia, Spain), Roberto Decarli (INAF – Astrophysics and Space Science Observatory, Italy), Brian C. Lemaux (International Gemini Observatory/NSF NOIRLab, USA, Institute of Astrophysics, Italy), Marta Volonteri (Paris Institute of Astrophysics, France), Francesca Civano (NASA Goddard Space Flight Center, USA), Sukyoung K. Yi (Department of Astronomy and Yonsei University Observatory, Republic of Korea), San Han (Department of Astronomy and Yonsei University Observatory, Republic of Korea), Mark Rawlings (International Gemini Observatory/NSF NOIRLab, USA), Denise Hung (International Gemini Observatory/NSF NOIRLab, USA)

NSF NOIRLab (U.S. National Science Foundation National Optical-Infrared Astronomy Research Laboratory), the U.S. center for ground-based optical-infrared astronomy, operates the International Gemini Observatory (a facility of NSF, NRC–Canada, ANID–Chile, MCTIC–Brazil, MINCyT–Argentina, and KASI–Republic of Korea), Kitt Peak National Observatory (KPNO), Cerro Tololo Inter-American Observatory (CTIO), the Community Science and Data Center (CSDC), and Vera C. Rubin Observatory (operated in cooperation with the Department of Energy’s SLAC National Accelerator Laboratory). It is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with NSF and is headquartered in Tucson, Arizona. The astronomical community is honored to have the opportunity to conduct astronomical research on I’oligam Du’ag (Kitt Peak) in Arizona, on Maunakea in Hawai‘i, and on Cerro Tololo and Cerro Pachón in Chile. We recognize and acknowledge the very significant cultural role and reverence that these sites have to the Tohono O’odham Nation, to the Native Hawaiian community, and to the local communities in Chile, respectively.

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Links

• Read the paper
• Chandra press release
• ICE-CSIC press release
• INAF press release
• JWST website
• Check out other NOIRLab Science Releases

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Contacts:

Hyewon Suh
Associate Scientist
International Gemini Observatory/NSF NOIRLab
Email: hyewon.suh@noirlab.edu

Julia Scharwächter
Scientist
International Gemini Observatory/NSF NOIRLab
Email: julia.scharwaechter@noirlab.edu

Josie Fenske
Jr. Public Information Officer
NSF NOIRLab
Email: josie.fenske@noirlab.edu

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Space oddity: Most distant rotating disc galaxy found

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The REBELS-25 galaxy

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ALMA image and motion of the cold gas in REBELS-25 (side-by-side)

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ALMA image of the cold gas in REBELS-25

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Motion of the cold gas in REBELS-25 as seen by ALMA

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Infrared image of stars and galaxies near the REBELS-25 galaxy

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Videos

PR Video eso2415a
Most distant rotating galaxy yet is a space oddity | ESO News

PR Video eso2415b
Zooming in on REBELS-25

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Researchers have discovered the most distant Milky-Way-like galaxy yet observed. Dubbed REBELS-25, this disc galaxy seems as orderly as present-day galaxies, but we see it as it was when the Universe was only 700 million years old. This is surprising since, according to our current understanding of galaxy formation, such early galaxies are expected to appear more chaotic. The rotation and structure of REBELS-25 were revealed using the Atacama Large Millimeter/submillimeter Array (ALMA), in which the European Southern Observatory (ESO) is a partner.

The galaxies we see today have come a long way from their chaotic, clumpy counterparts that astronomers typically observe in the early Universe. “According to our understanding of galaxy formation, we expect most early galaxies to be small and messy looking,” says Jacqueline Hodge, an astronomer at Leiden University, the Netherlands, and co-author of the study.

These messy, early galaxies merge with each other and then evolve into smoother shapes at an incredibly slow pace. Current theories suggest that, for a galaxy to be as orderly as our own Milky Way — a rotating disc with tidy structures like spiral arms — billions of years of evolution must have elapsed. The detection of REBELS-25, however, challenges that timescale.

In the study, accepted for publication in Monthly Notices of the Royal Astronomical Society, astronomers found REBELS-25 to be the most distant strongly rotating disc galaxy ever discovered. The light reaching us from this galaxy was emitted when the Universe was only 700 million years old — a mere five percent of its current age (13.8 billion) — making REBELS-25’s orderly rotation unexpected. “Seeing a galaxy with such similarities to our own Milky Way, that is strongly rotation-dominated, challenges our understanding of how quickly galaxies in the early Universe evolve into the orderly galaxies of today's cosmos,” says Lucie Rowland, a doctoral student at Leiden University and first author of the study.

REBELS-25 was initially detected in previous observations by the same team, also conducted with ALMA, which is located in Chile’s Atacama Desert. At the time, it was an exciting discovery, showing hints of rotation, but the resolution of the data was not fine enough to be sure. To properly discern the structure and motion of the galaxy, the team performed follow-up observations with ALMA at a higher resolution, which confirmed its record-breaking nature. “ALMA is the only telescope in existence with the sensitivity and resolution to achieve this,” says Renske Smit, a researcher at Liverpool John Moores University in the UK and also a co-author of the study.

Surprisingly, the data also hinted at more developed features similar to those of the Milky Way, like a central elongated bar, and even spiral arms, although more observations will be needed to confirm this. “Finding further evidence of more evolved structures would be an exciting discovery, as it would be the most distant galaxy with such structures observed to date,” says Rowland.

These future observations of REBELS-25, alongside other discoveries of early rotating galaxies, will potentially transform our understanding of early galaxy formation, and the evolution of the Universe as a whole.

Source: ESO/News

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More information

This research is presented in a paper entitled “REBELS-25: Discovery of a dynamically cold disc galaxy at z=7.31” to appear in Monthly Notices of the Royal Astronomical Society.

The observations were conducted as part of the ALMA Large Program REBELS: Reionization Era Bright Emission Lines Survey.

The team is composed of L. E. Rowland (Leiden Observatory, Leiden University, the Netherlands [Leiden]), J. Hodge (Leiden), R. Bouwens (Leiden), P. M. Piña (Leiden), A. Hygate (Leiden), H. Algera (Astrophysical Science Center, Hiroshima University, Japan [HASC]; National Astronomical Observatory of Japan, Japan), M. Aravena (Núcleo de Astronomía, Facultad de Ingeniería y Ciencias, Universidad Diego Portales, Chile), R. Bowler (Jodrell Bank Centre for Astrophysics, University of Manchester, UK), E. da Cunha (International Centre for Radio Astronomy Research, University of Western Australia, Australia; ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions), P. Dayal (Kapteyn Astronomical Institute, University of Groningen, the Netherlands), A. Ferrara (Scuola Normale Superiore, Italy [SNS]), T. Herard-Demanche (Leiden), H. Inami (HASC), I. van Leeuwen (Leiden), I. de Looze (Sterrenkundig Observatorium, Ghent University, Belgium), P. Oesch (Department of Astronomy, University of Geneva, Switzerland; Cosmic Dawn Center, Denmark), A. Pallottini (SNS), S. Phillips (Astrophysics Research Institute, Liverpool John Moores University, UK [LJMU]), M. Rybak (Faculty of Electrical Engineering, Delft University of Technology, the Netherlands; Leiden; Netherlands Institute for Space Research, the Netherlands), S. Schouws (Leiden), R. Smit (LJMU), L. Sommovigo (Center for Computational Astrophysics, Flatiron Institute, USA), M. Stefanon (Departament d’Astronomia i Astrofísica, Universitat de València, Spain; Grupo de Astrofísica Extragaláctica y Cosmología, Universitat de València, Spain), P. van der Werf (Leiden).

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of ESO, the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science and Technology Council (NSTC) in Taiwan and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI). ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

The European Southern Observatory (ESO) enables scientists worldwide to discover the secrets of the Universe for the benefit of all. We design, build and operate world-class observatories on the ground — which astronomers use to tackle exciting questions and spread the fascination of astronomy — and promote international collaboration for astronomy. Established as an intergovernmental organisation in 1962, today ESO is supported by 16 Member States (Austria, Belgium, Czechia, Denmark, France, Finland, Germany, Ireland, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom), along with the host state of Chile and with Australia as a Strategic Partner. ESO’s headquarters and its visitor centre and planetarium, the ESO Supernova, are located close to Munich in Germany, while the Chilean Atacama Desert, a marvellous place with unique conditions to observe the sky, hosts our telescopes. ESO operates three observing sites: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope and its Very Large Telescope Interferometer, as well as survey telescopes such as VISTA. Also at Paranal ESO will host and operate the Cherenkov Telescope Array South, the world’s largest and most sensitive gamma-ray observatory. Together with international partners, ESO operates ALMA on Chajnantor, a facility that observes the skies in the millimetre and submillimetre range. At Cerro Armazones, near Paranal, we are building “the world’s biggest eye on the sky” — ESO’s Extremely Large Telescope. From our offices in Santiago, Chile we support our operations in the country and engage with Chilean partners and society.

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Links

• Research paper
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• For scientists: got a story? Pitch your research

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Contacts

Lucie Rowland
Leiden Observatory, University of Leiden
Leiden, The Netherlands
Tel: +31 71 527 2727
Email: lrowland@strw.leidenuniv.nl

Jacqueline Hodge
Leiden Observatory, University of Leiden
Leiden, The Netherlands
Tel: +31 71 527 8450
Email: hodge@strw.leidenuniv.nl

Renske Smit
Astrophysics Research Institute, Liverpool John Moores University
Liverpool, UK
Tel: +44-151-231-2922
Email: R.Smit@ljmu.ac.uk

Bárbara Ferreira
ESO Media Manager
Garching bei München, Germany
Tel: +49 89 3200 6670
Cell: +49 151 241 664 00
Email: press@eso.org

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Little Red Dots and Big Black Holes

Images of six "little red dot" galaxies from JWST.
Credit: NASA/ESA/CSA/I. Labbe

Title: A Census of Photometrically Selected Little Red Dots at 4 < z < 9 in JWST Blank Fields
Authors: Vasily Kokorev et al.
First Author’s Institution: Kapteyn Astronomical Institute
Status: Accepted to ApJ

Imagine you peek into a kindergarten class and, to your shock, you see that all the children are well over 6 feet tall. That is precisely how astronomers felt when data from JWST showed galaxies with massive black holes just a few hundred million years after the birth of the universe. Some of these black holes have been measured to be a million times more massive than the mass of our Sun, and astronomers are puzzled as to how they could have gained so much mass in such a short time.

The earliest galaxies likely to host these black holes show up as little red dots in the images JWST took of the early universe (as seen in the long exposure images; see the bottom image in Figure 1). They are believed to be compact (with a small radius) galaxies with a Type I active galactic nucleus and obscured (covered by dust), which accounts for their red color and why they are easily observed in the infrared. The spectrum of the galaxy has a “V” shape, a blue continuum from the unobscured part of the active galactic nucleus in the galaxy, and a red continuum from the obscured part (see Figure 1). These little red dots have appeared in several images taken by JWST, hinting that plenty of massive black holes are lurking in the early universe.

Figure 1: The characteristic spectrum of little red dots (on the left), with the compact source contributing to the dust-free blue color in the continuum (top right) and the dust-reddened part (bottom right). Adapted from Kokorev et al. 2024

Where You Look Matters!

It is vital to systematically look at these little red dot galaxies to understand how many massive black holes were in the early universe. Two factors can introduce biases in the counting of these galaxies. One is the phenomenon of cosmic variance: is JWST just preferentially looking in a direction with many little red dots, or should we expect the same number even when it looks at different parts of the universe? The other is how crowded it is in the direction in which you are observing: if you have a lot of stars in the direction you are looking, they could be misclassified as little red dots or vice versa. If you happen to have plenty of massive galaxy clusters in the direction you are looking, they may create an illusion that more of these little red dots exist than their true numbers (a phenomenon known as gravitational lensing).

To minimize the errors caused by these effects in determining the number of little red dots in the early universe, the authors of today’s research article specifically look at large areas (640 arcminutes2) of the sky by combining JWST data from various programs. This would minimize the effects of cosmic variance as you can measure the numbers over a bigger area of the sky. They also look specifically at data in blank fields (defined here as areas on the sky without galaxy clusters), which helps them determine the accurate number of objects per unit volume. All these galaxies are photometrically selected (i.e., chosen only from looking at images rather than spectra), meaning there is limited spectroscopic data to help confirm what kind of objects they are. Galaxies are determined to be little red dots based on their red colors and how compact they are in the images. Using the obtained fluxes, the authors then construct spectral energy distributions to determine the redshifts (z) of the sample. Limiting the sample to z > 4 (for the early universe), the authors end up with 260 little red dot galaxies.

Do Not Judge a Galaxy by Its Size (in Your JWST Image!)

On calculating the total luminosity of the little red dots and comparing it to their redshifts, the authors find a large number of bright little red dots at redshift of z = 5 (around a billion years after the beginning of the universe). The number of little red dots is almost 100 times more than the number of ultraviolet-selected quasars, which are active galactic nuclei identified using another method. They also find that computer models are unable to reproduce the high fraction of the bright galaxies they uncover at high redshifts (left side of Figure 2). The authors derive the mass of the black holes at redshifts of z = 4.5–6.5 to be around 106–108 solar masses, indicating that these black holes were already massive a few hundred million years after the Big Bang. They find deviations from the predicted number densities of massive black holes at these redshifts from galaxy simulations. This is likely because the galaxies that host more gigantic black holes are very dusty, and thus, their spectra do not have any blue continuum. They may then be missed from selections of little red dots as one of the factors it depends on is the characteristic “V”-shaped spectrum, which would need a contribution from the blue continuum (right side of Figure 2).

Figure 2: Left: The number density of the little red dots as a function of luminosity at 6.5 < z < 8.5 with the predicted values from simulations indicated by the blue solid line. Right: The number density as a function of black hole mass at 4.5 < z < 6.5. The observed number density of more massive black holes is lower than the values predicted by simulations. Adapted from Kokorev et al. 2024

While spectroscopy is a more reliable method to identify massive black holes, many galaxies that host black holes can still be picked out using near-infrared colors and photometry, which is a much less expensive technique. The challenge lies in ensuring that the photometrically selected sources are reliable, and the authors of today’s article made great use of this technique. Follow-up spectroscopic studies of these photometrically selected samples can help us further understand the exact nature of the black holes. Such studies are already underway, and we can look forward to finally making sense of how these black holes became so massive in such a short time after the formation of the universe!

Original astrobite edited by Delaney Dunne.

Source: American Astronomical Society/AASNova

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About the author, Archana Aravindan:

I am a PhD candidate at the University of California, Riverside, where I study black hole activity in small galaxies. When I am not looking through some incredible telescopes, you can usually find me reading, thinking about policy, or learning a cool language!

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Editor’s Note: Astrobites is a graduate-student-run organization that digests astrophysical literature for undergraduate students. As part of the partnership between the AAS and astrobites, we occasionally repost astrobites content here at AAS Nova. We hope you enjoy this post from astrobites; the original can be viewed at astrobites.org.

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Brightest and fastest-growing: astronomers identify record-breaking quasar

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Artist’s impression of the record-breaking quasar J0529-4351

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Wide-field of the region around the quasar J0529-4351

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Videos

 

PR Video eso2402a
Astronomers identify record-breaking quasar | ESOcast Light

 

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Artist’s impression of the record-breaking quasar J0529-4351

 

PR Video eso2402c
Zooming in on the record-breaking quasar J0529-4351

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Using the European Southern Observatory’s (ESO) Very Large Telescope (VLT), astronomers have characterised a bright quasar, finding it to be not only the brightest of its kind, but also the most luminous object ever observed. Quasars are the bright cores of distant galaxies and they are powered by supermassive black holes. The black hole in this record-breaking quasar is growing in mass by the equivalent of one Sun per day, making it the fastest-growing black hole to date.

The black holes powering quasars collect matter from their surroundings in a process so energetic that it emits vast amounts of light. So much so that quasars are some of the brightest objects in our sky, meaning even distant ones are visible from Earth. As a general rule, the most luminous quasars indicate the fastest-growing supermassive black holes.

“We have discovered the fastest-growing black hole known to date. It has a mass of 17 billion Suns, and eats just over a Sun per day. This makes it the most luminous object in the known Universe,” says Christian Wolf, an astronomer at the Australian National University (ANU) and lead author of the study published today in Nature Astronomy. The quasar, called J0529-4351, is so far away from Earth that its light took over 12 billion years to reach us.

The matter being pulled in toward this black hole, in the form of a disc, emits so much energy that J0529-4351 is over 500 trillion times more luminous than the Sun [1]. “All this light comes from a hot accretion disc that measures seven light-years in diameter — this must be the largest accretion disc in the Universe," says ANU PhD student and co-author Samuel Lai. Seven light-years is about 15 000 times the distance from the Sun to the orbit of Neptune.

And, remarkably, this record-breaking quasar was hiding in plain sight. “It is a surprise that it has remained unknown until today, when we already know about a million less impressive quasars. It has literally been staring us in the face until now,” says co-author Christopher Onken, an astronomer at ANU. He added that this object showed up in images from the ESO Schmidt Southern Sky Survey dating back to 1980, but it was not recognised as a quasar until decades later.

Finding quasars requires precise observational data from large areas of the sky. The resulting datasets are so large, researchers often use machine-learning models to analyse them and tell quasars apart from other celestial objects. However, these models are trained on existing data, which limits the potential candidates to objects similar to those already known. If a new quasar is more luminous than any other previously observed, the programme might reject it and classify it instead as a star not too distant from Earth.

An automated analysis of data from the European Space Agency’s Gaia satellite passed over J0529-4351 for being too bright to be a quasar, suggesting it to be a star instead. The researchers identified it as a distant quasar last year using observations from the ANU 2.3-metre telescope at the Siding Spring Observatory in Australia. Discovering that it was the most luminous quasar ever observed, however, required a larger telescope and measurements from a more precise instrument. The X-shooter spectrograph on ESO’s VLT in the Chilean Atacama Desert provided the crucial data.

The fastest-growing black hole ever observed will also be a perfect target for the GRAVITY+ upgrade on ESO’s VLT Interferometer (VLTI), which is designed to accurately measure the mass of black holes, including those far away from Earth. Additionally, ESO’s Extremely Large Telescope (ELT), a 39-metre telescope under construction in the Chilean Atacama Desert, will make identifying and characterising such elusive objects even more feasible.

Finding and studying distant supermassive black holes could shed light on some of the mysteries of the early Universe, including how they and their host galaxies formed and evolved. But that’s not the only reason why Wolf searches for them. “Personally, I simply like the chase,” he says. “For a few minutes a day, I get to feel like a child again, playing treasure hunt, and now I bring everything to the table that I have learned since.”

Source: ESO/News

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Notes

[1] A few years ago, NASA and the European Space Agency reported that the Hubble Space Telescope had discovered a quasar, J043947.08+163415.7, as bright as 600 trillion Suns. However, that quasar’s brightness was magnified by a ‘lensing’ galaxy, located between us and the distant quasar. The actual luminosity of J043947.08+163415.7 is estimated to be equivalent to about 11 trillion Suns (1 trillion is a million million: 1 000 000 000 000 or 10¹²).

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More information

This research was presented in a paper titled “The accretion of a solar mass per day by a 17-billion solar mass black hole” to appear in Nature Astronomy (doi:10.1038/s41550-024-02195-x).

The team is composed of Christian Wolf (Research School of Astronomy and Astrophysics, Australian National University, Australia [ANU] and Centre for Gravitational Astrophysics, Australian National University, Australia [CGA]), Samuel Lai (ANU), Christopher A. Onken (ANU), Neelesh Amrutha (ANU), Fuyan Bian (European Southern Observatory, Chile), Wei Jeat Hon (School of Physics, University of Melbourne, Australia [Melbourne]), Patrick Tisserand (Sorbonne Universités, CNRS, UMR 7095, Institut d’Astrophysique de Paris, France), and Rachel L. Webster (Melbourne).

The European Southern Observatory (ESO) enables scientists worldwide to discover the secrets of the Universe for the benefit of all. We design, build and operate world-class observatories on the ground — which astronomers use to tackle exciting questions and spread the fascination of astronomy — and promote international collaboration for astronomy. Established as an intergovernmental organisation in 1962, today ESO is supported by 16 Member States (Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Ireland, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom), along with the host state of Chile and with Australia as a Strategic Partner. ESO’s headquarters and its visitor centre and planetarium, the ESO Supernova, are located close to Munich in Germany, while the Chilean Atacama Desert, a marvellous place with unique conditions to observe the sky, hosts our telescopes. ESO operates three observing sites: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope and its Very Large Telescope Interferometer, as well as survey telescopes such as VISTA. Also at Paranal ESO will host and operate the Cherenkov Telescope Array South, the world’s largest and most sensitive gamma-ray observatory. Together with international partners, ESO operates ALMA on Chajnantor, a facility that observes the skies in the millimetre and submillimetre range. At Cerro Armazones, near Paranal, we are building “the world’s biggest eye on the sky” — ESO’s Extremely Large Telescope. From our offices in Santiago, Chile we support our operations in the country and engage with Chilean partners and society.

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Links

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Contacts

Christian Wolf
Australian National University
Canberra, Australia
Tel: +61(02)-61256373
Cell: +61(0)415330371
Email: christian.wolf@anu.edu.au

Samuel Lai
Australian National University
Canberra, Australia
Cell: +61 (0) 493418898
Email: samuel.lai@anu.edu.au

Christopher Onken
Australian National University
Canberra, Australia
Tel: +61(0) 26125 8039
Email: christopher.onken@anu.edu.au

Rachel L. Webster (study co-author)
University of Melbourne
Melbourne, Australia
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Email: r.webster@unimelb.edu.au

Bárbara Ferreira
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Rapid Increase in Oxygen in Early Universe

JWST infrared images of 6 galaxies from 500-700 million years after the birth of the Universe. All 6 have low oxygen abundances compared to modern galaxies. (Credit: NASA, ESA, CSA, K. Nakajima et al.) Download image (671KB)

Using new data from the James Webb Space Telescope, astronomers have measured the abundance of oxygen in the early Universe. The findings show that the amount of oxygen in galaxies increased rapidly within 500-700 million years after the birth of the Universe, and has remained as abundant as observed in modern galaxies since then. This early appearance of oxygen indicates that the elements necessary for life were present earlier than expected.

In the early Universe, shortly after the Big Bang, only light elements such as hydrogen, helium, and lithium existed. Heavier elements like oxygen were subsequently formed through nuclear fusion reactions within stars and dispersed into galaxies, primarily through events like supernova explosions. This ongoing process of element synthesis, unfolding over the vast expanse of cosmic history, created the diverse elements that constitute the world and living organisms around us.

A research team led by Kimihiko Nakajima at the National Astronomical Observatory of Japan used data from the James Webb Space Telescope (JWST) to measure the oxygen in 138 galaxies that existed in the first 2 billion years of the Universe. The team found that most of the galaxies had oxygen abundances similar to modern galaxies. But out of the 7 earliest galaxies in the sample, those that existed when the Universe was only 500-700 million years old, 6 of them had roughly half the predicted oxygen content.

This rapid increase in oxygen content occurred earlier than astronomers were expecting. This opens the possibility that with the necessary ingredients, like oxygen, already readily available in the early Universe that life may have appeared sooner than previously thought.

Source: National Radio Astronomy Observatory (NRAO)/News

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Detailed Article(s)

Rapid Increase in Oxygen in Early Universe

ICRR

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Release Information

Researcher(s) Involved in this Release

Kimihiko Nakajima (Project Assistant Professor @ National Astronomical Observatory of Japan)

Masami Ouchi (Professor @ National Astronomical Observatory of Japan, Professor @ Institute for Cosmic Ray Research, The University of Tokyo)

Yuichi Harikane (Assistant Professor @ Institute for Cosmic Ray Research, The University of Tokyo)
Yoshiaki Ono (Assistant Professor @ Institute for Cosmic Ray Research, The University of Tokyo)
Yuki Isobe (Doctoral Student @ Graduate School of Science, Tohoku University)
Hiroya Umeda (Doctoral Student @ Graduate School of Science, Tohoku University)
Masamune Oguri (Professor @ Center for Frontier Science, Chiba University)
Yechi Zhang (JSPS Postdoctoral Fellow @ National Astronomical Observatory of Japan)

Coordinated Release Organization(s)

National Astronomical Observatory of Japan
The University of Tokyo

Paper(s)

Kimihiko Nakajima et al. “JWST Census for the Mass-Metallicity Star Formation Relations at z = 4-10 with Self-consistent Flux Calibration and Proper Metallicity Calibrators”, in The Astrophysical Journal Supplement Series, DOI: 10.3847/1538-4365/acd556

Related Link(s)

• Rapid Increase in Oxygen in Early Universe (Division of Science)

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SPICE connects stellar feedback in the first galaxies and cosmic reionisation

These images show the four most massive galaxies from each of the three simulation models. The top two rows show "bursty" feedback, the middle two rows show "smooth" feedback, and the bottom two rows show a mixture of the two, where each galaxy is shown both face-on (top) and edge-on (bottom). The galaxies in each column occupy the exact same environment in every simulation. The effect of different stellar feedback models is evident as the bursty feedback model produces elliptical-like galaxies whereas the smooth and intermediate models predominantly produce spiral-like galaxies. © MPA

The first billion years saw the transformation of a cold neutral Universe to a hot and ionised one. This Epoch of Reionisation is thought to come about from stellar radiation from the first galaxies. Understanding the nature of the galaxies that drove reionisation remains a key question. Scientists at MPA have designed a novel suite of simulations to systematically understand how different modes of energy and mass injection from stars affect the first galaxies. According to these new models, subtle differences in the behaviour of stellar feedback drive profound differences in the morphologies of galaxies and the speed at which they ionise the universe. Combining these findings with the latest observations will help constrain feedback models in the first billion years of the Universe.

Some 300,000 years after the Big Bang, for the first time, protons and free electrons formed hydrogen and helium atoms – the Universe was mostly neutral. In the following billion years, however, the vast majority of hydrogen became ionised. This transition from a neutral to an ionised state is known as the "epoch of reionisation". For this to happen, ionising photons had to escape from galaxies. Massive stars emit ionising radiation and at the end of their lives, they die in supernova explosions, releasing mass and energy into gas around them. These processes are termed "stellar feedback", and change the physical structure of the so-called interstellar medium. How this stellar feedback changes the properties of the first galaxies and in particular the gas within these galaxies is poorly understood, but it is key to interpret the recent flood of observations of the early Universe from the James Webb Space telescope.

In the last decade, advancements in high performance computing and theoretical models have allowed scientists to reproduce observations of the first billion years of the Universe. Even though these sophisticated simulations were able to combine radiation and hydrodynamics, due to the computational costs, they typically explore only one of the many possible models of stellar feedback. A team of researchers at MPA led by Aniket Bhagwat, therefore, developed a new suite of simulations called SPICE to systematically test different models and, in particular, to look at connections between stellar feedback and the properties of galaxies that drive reionisation, which could be tested through observations.

The SPICE simulations follow the hydrodynamical evolution of gas, including key processes like star formation and supernova explosions, while tracking the propagation of radiation emitted by those stars. In particular, they include three different modes of stellar feedback: "bursty", where supernovae explode in clustered bursts; "smooth", where supernova explosions are spread out in time; or a mix of the two. And indeed, the simulations show that differences in the strength and behaviour of feedback can have dramatic effects on the morphology of the galaxies. Bursty feedback preferentially produces red and passive galaxies (elliptical-like), whereas smooth feedback produces mostly galaxies that are blue and star forming (spiral-like).

Evolution of ionized hydrogen

The animations show the process of reionisation in SPICE for the three different feedback models over the first billion years of the universe (from redshift ~24 to 5). The stars emit energetic photons that first ionize their surroundings in the form of bubbles. As more photons escape, these ionised bubbles expand to eventually coalesce and complete the process of reionisation. This process is much faster for the bursty feedback model.

What implications does this have for the process of reionisation? The researchers connected the morphologies of the galaxies to the fraction of ionising photons that manage to leave the galaxy; this quantity is called the “escape fraction”. They find that elliptical-like galaxies show a much higher escape fraction than spiral-like ones (by a factor of 20-50). Why does this happen? The bursts of energy due to the combined supernova explosions are able to substantially disturb the gas and punch low-density holes in the interstellar medium, through which the ionising photons can escape easily. Without bursts, the feedback is unable to disturb the gas enough to allow photons to escape en masse. Therefore, bursty feedback models allow for faster reionisation.

Overall, the new SPICE simulations demonstrate for the first time how sensitive cosmic reionisation and galaxy morphologies are to the mode of stellar feedback, marking a step forward in our understanding of the first billion years of the Universe.

Temperature evolution of the simulations

These animations show how the temperature changes in the simulations. Bright red bubbles show hot gas ejected from supernova explosions. Bright white bubbles show regions where ionising photons escape galaxies and ionise their surroundings. The different stellar feedback models produce widely different final states of the simulated universes.

Simulations and data analysis were carried out on the RAVEN and COBRA supercomputers at MPCDF.

Source: Max Planck Institute for Astrophysics/News

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Author:

Aniket Bhagwat
PhD student
2270
mrmgehlm@mpa-garching.mpg.de

For all authors: Aniket Bhagwat, Tiago Costa, Benedetta Ciardi, Ruediger Pakmor, Enrico Garaldi

Original publication:

Aniket Bhagwat, Tiago Costa, Benedetta Ciardi, Ruediger Pakmor, Enrico Garaldi
SPICE: the connection between cosmic reionisation and stellar feedback in the first galaxies.

To be submitted to MNRAS

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ALMA Unveils Cosmic Nursery and Stellar Graveyard in Most Remote Galaxy Ever Observed

The ALMA image of the galaxy MACS0416_Y1 located 13.2 billion light-years away, harboring the farthest ever dark nebula. The image spans approximately 15,000 light-years on each side. (Left) Radio images captured by ALMA depicting the dark nebula (emitting radio waves from dust, shown in red) and the emission nebula (emitting radio waves from oxygen, green), along with the image of stars captured by the Hubble Space Telescope (blue). Credit: ALMA (ESO/NAOJ/NRAO), Y. Tamura et al., NASA/ESA Hubble Space Telescope. (Right) Image captured by ALMA, only showing the radio waves emitted by the dust within the dark nebula. A vertically elongated elliptical cavity, a candidate for a superbubble, is visible in the central region." Credit: ALMA (ESO/NAOJ/NRAO), Y. Tamura et al.

The ALMA image of the galaxy MACS0416_Y1 located 13.2 billion light-years away, harboring the farthest ever dark nebula. The image spans approximately 15,000 light-years on each side. Radio images captured by ALMA depicting the dark nebula (emitting radio waves from dust, shown in red) and the emission nebula (emitting radio waves from oxygen, green), along with the image of stars captured by the Hubble Space Telescope (blue). Credit: ALMA (ESO/NAOJ/NRAO), Y. Tamura et al., NASA/ESA Hubble Space Telescope. Credit: ALMA (ESO/NAOJ/NRAO), Y. Tamura et al.

The ALMA image of the galaxy MACS0416_Y1 located 13.2 billion light-years away, harboring the farthest ever dark nebula. The image spans approximately 15,000 light-years on each side. Image captured by ALMA, only showing the radio waves emitted by the dust within the dark nebula. A vertically elongated elliptical cavity, a candidate for a superbubble, is visible in the central region." Credit: ALMA (ESO/NAOJ/NRAO), Y. Tamura et al.

Scientific Paper

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Astronomers glean vital insights into the birth and death of stars through unprecedented high-resolution imaging of an ancient galaxy.

An international team of astronomers, spearheaded by Professor Yoichi Tamura of Nagoya University, has achieved an astronomical tour de force by capturing high-resolution images of a fledgling galaxy that existed a mere 600 million years after the Big Bang. These groundbreaking images, obtained with the Atacama Large Millimeter/submillimeter Array (ALMA), have shed light on previously unseen structures formed through the interplay of dark and emission nebulae.

The ALMA radio images paint a captivating tapestry where these nebulae coalesce to form a gargantuan cavity reminiscent of a ‘superbubble’. This superbubble is believed to have been formed by the birth of vibrant stars and the subsequent shockwaves created by supernova explosions. These revelations are paramount for understanding the enigmatic processes associated with the formation of galaxies and the cycles of stellar birth and death.

The team commenced its pioneering exploration into ultra-distant galaxies with ALMA in 2012 and achieved a major breakthrough in 2016 by detecting radio waves from oxygen in a record-setting distant galaxy. They continued to push the envelope, identifying the most distant galaxy ever known by detecting radio waves emitted by oxygen 13.28 billion light-years away in 2018.

In 2019, the researchers further refined their discoveries by detecting radio waves emitted by both oxygen and dust in another galaxy called MACS0416_Y1, located 13.2 billion light-years away. The detection of dust in the early Universe, where the cycle of the reincarnation of stars had not yet repeated extensively, was a remarkable finding that marked a milestone in our understanding of the Universe.

One of the remarkable findings from these observations is the presence of dark nebulae in the early universe. Dark nebulae are dense clouds of cold dust and gas that obscure starlight and are known to be the crucibles where stars are born. The team’s intricate observations reveal the life cycle within these dark nebulae; stars are born, they live, and they die, giving rise to new stars.

In their most recent endeavor, the research team achieved unparalleled high-resolution images of MACS0416_Y1. By configuring ALMA’s antennas akin to a zoom lens and employing a 28-hour-long exposure, they were able to discern the origins of radio waves emitted by dust and oxygen, depicting how emission and dark nebulae are closely intertwined, each carving out its own space. This delicate dance is indicative of a process where new stars born within the dark nebulae ionize the surrounding gas.

Moreover, the images reveal a colossal cavity, spanning approximately 1,000 light-years, at the center of the galaxy, which is possibly a superbubble. Prior studies indicated that MACS0416_Y1 was producing stars at an astonishing rate, about 100 times higher than that of the Milky Way. This frenzied pace of star formation likely led to the creation of this superbubble through consecutive supernova explosions.

The team was also able to analyze the motion of gas within the nebulae, finding it to be in a turbulent state, with speeds reaching up to an astounding 200,000 kilometers per hour. “Under such turbulent conditions, it is suggested that stars may form as massive clusters,” remarks Professor Tamura. He further noted that these massive star clusters are characteristic of galaxies in the early Universe. Dr. Takuya Hashimoto from the University of Tsukuba lauded ALMA’s performance, stating, “It corresponds to capturing the extremely weak light emitted by two fireflies located 3 centimeters apart on the summit of Mount Fuji as seen from Tokyo, and being able to distinguish between those two fireflies. The significance of this study lies in bringing out the ultimate performance of ALMA, leading to an understanding of the formation of early galaxies, the life and death of stars, and the ecocycle of matter in the Universe.”

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Additional Information

These observation results were published as Yoichi Tamura et al. "The 300-parsec resolution imaging of a z = 8.31 galaxy: Turbulent ionized gas and potential stellar feedback 600 million years after the Big Bang" in the Astrophysical Journal on July 13, 2023 (DOI: 10.3847/1538-4357/acd637).

This work is supported by a Grant-in-Aid from the Japan Society for the Promotion of Science (17H06130, 19H01931, 20H01951, 20H05861, 20K22358, 21H01128, 21H04496, 22J21948, 22H01258, 22H04939), NAOJ ALMA Scientific Research Grant (2018-09B, 2020-16B), and Leading Initiative for Excellent Young Researchers, MEXT, Japan (HJH02007).

This Press Releases is adapted from the original text released by the National Astronomical Observatory of Japan, an ALMA partner on behalf of East Asia.

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Organization for Astronomical Research in the Southern Hemisphere (ESO), the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science and Technology Council (NSTC) in Taiwan and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).

ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

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Contacts:

Valeria Foncea
Education and Public Outreach Manager
Joint ALMA Observatory Santiago - Chile
Phone: +56 2 2467 6258
Cel: +56 9 7587 1963
Email: valeria.foncea@alma.cl

Naoko Inoue
EPO officer, ALMA Project
National Astronomical Observatory of Japan (NAOJ)
Email: naoko.inoue@nao.ac.jp

Source: Alma Observatory/Press Release

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Signature of Very Massive First Stars Recorded in a Milky Way Star

Figure 1: Artist's rendition of massive, luminous first-generation stars in the Universe which would form a cluster. The most massive ones should have exploded and ejected material providing heavy elements in the surrounding gas clouds. A high resolution image is here (2.6 MB). (Credit: NAOC)

Astronomers have discovered a star on the outskirts of the Milky Way Galaxy with a chemical composition unlike anything they have ever seen. It matches theoretical expectations for the chemical footprint left behind by very massive, very early stars. This is the clearest evidence yet that the first stars included very massive star.

What is the nature of the first stars formed in the Universe? This is one of the most important questions in understanding how stars, galaxies, and the large-scale structures of the Universe formed after the Big Bang (Note 1). The first stars were born from gas clouds containing only hydrogen and helium, and nuclear fusion inside stars and supernova explosions have created new elements, the first steps in the formation of a diverse world of matter.

Theories predict that the first stars may have included many very massive stars that are rarely seen in the current Universe. Stars exceeding 140 times the mass of the Sun may have changed the environment of the Universe with intense ultraviolet radiation, and may have had a significant impact on the formation of the next generation of stars by very energetic supernovae (Pair-Instability Supernovae: PISNe) (Note 2).

However, there is a lack of clear observational evidence for the existence of such supernovae caused by very massive stars. Great efforts have been made to observe very old stars in the Milky Way Galaxy, along with observations of distant galaxies and intergalactic matter. Some of the old stars were born from gas clouds that captured elements ejected by the first stars, and their chemical compositions record the material produced by the first supernovae. Since PISNe caused by very massive stars produce chemical compositions that are very different from those of ordinary core-collapse supernovae, we can expect to identify the signature of very massive stars among old stars (Note 3).

A team of astronomers from the National Astronomical Observatory of Japan (NAOJ), the National Astronomical Observatories of China (NAOC), and other institutes have conducted studies using the Chinese survey telescope LAMOST to identify early generation stars in the Milky Way Galaxy and measured their detailed chemical compositions using the Subaru Telescope (Note 4). Among them, they have discovered LAMOST J101051.9+235850.2 (hereafter J1010+2358) with characteristic chemical compositions produced by a pair-instability supernova (Figures 2 and 3). This is the clearest trace of such supernovae found to date, and strongly supports the theory that stars that have masses more than 140 times larger than the mass of the Sun certainly formed in the early Universe.

Figure 2: An optical image of LAMOST J101051.9+235850.2 taken from SDSS. This star exists in the direction of the constellation Leo with a distance of 3000 light-years. This is a main-sequence star with a mass slightly smaller than the mass of the Sun. (Credit: SDSS/NAOJ)

Figure 3: Elemental abundances of LAMOST J101051.9+235850.2 (red circles) and predictions from supernova models (lines). The upper panel shows a comparison with the supernova model for a progenitor with 10 solar masses, which does not explain the observation. The middle shows a comparison with a 85 solar mass model, which is still insufficient to explain elements like Na, Mg, Mn and Co. The bottom shows a comparison with the pair-instability model for a very massive star with 260 solar masses, which best explains the observation. (Credit: NAOC)

"The peculiar odd-even variance, along with deficiencies of sodium and α-elements in this star, are consistent with the prediction of primordial PISN from first-generation stars with 260 solar masses," says Dr. XING Qianfan, first author of the study.

The discovery of J1010+2358 is direct evidence of the hydrodynamical instability due to electron–positron pair production in the theory of very massive star evolution. The creation of electron–positron pairs reduces thermal pressure inside the core of a very massive star and leads to a partial collapse.

"It provides an essential clue to constraining the initial mass function in the early universe," says Prof. ZHAO Gang, corresponding author of the study. "Before this study, no evidence of supernovae from such massive stars has been found in the metal-poor stars."

Professor AOKI Wako of the National Astronomical Observatory of Japan, who has been leading the observing programs with the Subaru Telescope in the collaboration, says, "Our team has been working for nearly 10 years to study stars found by LAMOST in detail using the Subaru Telescope. Searching for evidence of the existence of very massive stars, which is thought to be unique to first stars, has been a challenge we have been working on for many years. We have achieved this major goal by this study."

What percentage of the first stars were very massive? This is the next big question that needs to be answered, and to do so, we need to explore many more stars and measure their chemical compositions.

Movie: Message from Professor AOKI Wako of the National Astronomical Observatory of Japan, who has been leading the observing programs with the Subaru Telescope in the collaboration. (Credit: NAOJ)

These results appeared as Xing et al. "A metal-poor star with abundances from a pair instability supernova" in Nature on June 7, 2023.

Notes:

(Note 1) Starting from initial non-uniform distributions (i.e., inhomogeneities) in the dark matter density that existed in the Universe after the Big Bang, matter increasingly gathers in areas of high density due to the effect of gravitational forces. The first stars would have formed in regions with the highest density of matter.

(Note 2) Previous observations with the Subaru Telescope have also found stars with peculiar compositions that cannot be explained by ordinary core collapse supernovae (Note 3), suggesting the existence of very massive stars, but there were still problems that could not be explained by theoretical models of supernovae. (Subaru Telescope August 21, 2014 Press Release)

(Note 3) At the end of their evolution, massive stars with masses dozens of times greater than the mass of the Sun undergo a supernova explosion with the collapse of the central part to form a black hole or neutron star (core collapse supernova). They eject a wide variety of elements ranging from carbon to iron. On the other hand, massive stars with masses 140 times greater than the mass of the Sun become so hot at their centers that they collapse to form electron-positron pairs, which explode in runaway nuclear fusion (pair-instability supernovae). Furthermore, when the mass of a star exceeds 300 times the mass of the Sun, even runaway nuclear fusion cannot stop the star’s gravitational collapse, and it is believed that the star becomes a black hole without an explosion.

(Note 4) The team searched for low metal stars using the survey telescope. LAMOST J101051.9+235850.2 is one of the stars that had been suggested to have a unique composition during the LAMOST search. The detailed chemical composition was successfully determined from the high-resolution spectrum obtained with HDS on the Subaru Telescope.

Relevant Links

• NAOJ June 7, 2023 Press Release
• NAOC June 7, 2023 Press Release

Source: Subaru Telescope

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