SPACE
The James Webb Space Telescope captures a staggering quasar-galaxy merger in the remote universe
An international research group led by the Italian National Institute for Astrophysics (INAF) utilised the the James Webb Space Telescope to witness the dramatic interaction between a quasar and two massive satellite galaxies in the distant universe
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MAP OF THE LINE EMISSION OF HYDROGEN (IN RED AND BLUE) AND OXYGEN (IN GREEN) IN THE PJ308-21 SYSTEM, SHOWN AFTER MASKING THE LIGHT FROM THE CENTRAL QUASAR ("QSO"). THE DIFFERENT COLOURS OF THE QUASAR'S HOST GALAXY AND COMPANION GALAXIES IN THIS MAP REVEAL THE PHYSICAL PROPERTIES OF THE GAS WITHIN THEM.
view moreCREDIT: DECARLI/INAF/A&A 2024
Observations of this quasar (already described by the same authors in another study published last May), one of the first studied with NIRSpec when the universe was less than a billion years old (redshift z = 6.2342), have revealed data of sensational quality: the instrument “captured” the quasar’s spectrum with an uncertainty of less than 1% per pixel. The host galaxy of PJ308–21 shows high metallicity and photoionisation conditions typical of an active galactic nucleus (AGN), whereas one of the satellite galaxies exhibits low metallicity (which refers to the abundance of chemical elements heavier than hydrogen and helium) and photoionisation induced by star formation; a higher metallicity characterises the second satellite galaxy, which is partially photoionised by the quasar.
The discovery has enabled astronomers to determine the mass of the supermassive black hole at the centre of the system (about 2 billion solar masses). It also confirmed that both the quasar and the surrounding galaxies are highly evolved in mass and metal enrichment, and in constant growth. This has profound implications for our understanding of cosmic history and galaxies' chemical evolution, highlighting this research's transformative impact.
Roberto Decarli, a researcher at INAF in Bologna and first author of the article, explains: "Our study reveals that both the black holes at the centre of high-redshift quasars and the galaxies that host them undergo extremely efficient and tumultuous growth already in the first billion years of cosmic history, aided by the rich galactic environment in which these sources form". The data were obtained in September 2022 as part of Program 1554, one of the nine Italian-led projects of the first observation cycle of JWST. Decarli leads this program to observe the merger between the galaxy hosting the quasar (PJ308-21) and two of its satellite galaxies.
The observations were carried out in integral field spectroscopy mode: for each image pixel, the spectrum of the entire optical band (in the source rest frame) can be observed, shifted towards the infrared by the universe’s expansion. This allows for the study of various gas tracers (emission lines) using a 3D approach. Thanks to this technique, the team led by INAF detected spatially extended emissions from different elements, which were used to study the properties of the ionised interstellar medium, including the source and hardness of the photoionising radiation field, metallicity, dust obscuration, electron density and temperature, and star formation rate. Furthermore, the researchers marginally detected the starlight emission associated with companion sources.
Federica Loiacono, astrophysicist, research fellow and postdoc working at INAF, enthusiastically comments on the results: "Thanks to NIRSpec, for the first time we can study in the PJ308-21 system the optical band, rich in precious diagnostic data on properties of the gas near the black hole in the galaxy hosting the quasar and in the surrounding galaxies. We can see, for example, the emission of hydrogen atoms and compare it with the chemical elements produced by the stars to establish how rich the gas in galaxies is in metals. The experience in reducing and calibrating these data, some of the first collected with NIRSpec in integral field spectroscopy mode, has ensured a strategic advantage for the Italian community in managing similar data from other programs". Federica Loiacono is the Italian contact person for NIRSpec data reduction at the INAF JWST Support Center.
She adds: “Thanks to the sensitivity of the James Webb Space Telescope in the near and medium infrared, it was possible to study the spectrum of the quasar and companion galaxies with unprecedented precision in the distant universe. Only the excellent 'view' offered by JWST, with its unparalleled capabilities, can ensure these observations". The work represented a real "emotional rollercoaster", Decarli continues, "with the need to develop innovative solutions to overcome the initial difficulties in data reduction".
This transformative impact of the James Webb Space Telescope's onboard instruments underscores its crucial role in advancing astrophysical research: “Until a couple of years ago, data on the enrichment of metals (essential for understanding the chemical evolution of galaxies) were almost beyond our reach, especially at these distances. Now we can map them in detail with just a few hours of observation, even in galaxies observed when the universe was in its infancy", Decarli concludes.
Related journal article: "A quasar-galaxy merger at z ∼ 6.2: rapid host growth via accretion of two massive satellite galaxies”, by Roberto Decarli, Federica Loiacono, Emanuele Paolo Farina, Massimo Dotti, Alessandro Lupi, Romain A. Meyer, Marco Mignoli, Antonio Pensabene, Michael A. Strauss, Bram Venemans, Jinyi Yang, Fabian Walter, Julien Wolf, Eduardo Bañados, Laura Blecha, Sarah Bosman, Chris L. Carilli, Andrea Comastri, Thomas Connor, Tiago Costa, Anna-Christina Eilers, Xiaohui Fan, Roberto Gilli, Hyunsung D. Jun, Weizhe Liu, Madeline A. Marshall, Chiara Mazzucchelli, Marcel Neeleman, Masafusa Onoue, Roderik Overzier, Maria Anne Pudoka, Dominik A. Riechers, Hans-Walter Rix, Jan-Torge Schindler, Benny Trakhtenbrot, Maxime Trebitsch, Marianne Vestergaard, Marta Volonteri, Feige Wang, Huanian Zhang, Siwei Zou. Forthcoming in: Astronomy & Astrophysics.
METHOD OF RESEARCH
Observational study
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
A quasar-galaxy merger at z~6.2: Rapid host growth via the accretion of two massive satellite galaxies
Fresh wind blows from historical supernova
Elusive temporary star described in historical documents recreated using new computer model, shows it may have recently started generating stellar winds
UNIVERSITY OF TOKYO
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THIS ILLUSTRATION CHARTS THE EVOLUTION OF THE SNR 1181 REMNANT, FROM ITS CREATION WHEN A CARBON-OXYGEN-BASED WHITE DWARF AND OXYGEN-NEON WHITE DWARF MERGED, TO THE FORMATION OF ITS TWO SHOCK REGIONS.
view moreCREDIT: 2024 T. KO
A mysterious remnant from a rare type of supernova recorded in 1181 has been explained for the first time. Two white dwarf stars collided, creating a temporary “guest star,” now labeled supernova (SN) 1181, which was recorded in historical documents in Japan and elsewhere in Asia. However, after the star dimmed, its location and structure remained a mystery until a team pinpointed its location in 2021. Now, through computer modeling and observational analysis, researchers have recreated the structure of the remnant white dwarf, a rare occurrence, explaining its double shock formation. They also discovered that high-speed stellar winds may have started blowing from its surface within just the past 20-30 years. This finding improves our understanding of the diversity of supernova explosions, and highlights the benefits of interdisciplinary research, combining history with modern astronomy to enable new discoveries about our galaxy.
It is the year 1181 and in Japan the Genpei War (1180-85) has recently begun. It will lead to a shift in political power from aristocratic families to the new military-based shogunate, which will establish itself in the coastal city of Kamakura near modern-day Tokyo. A record of this tumultuous period was compiled in a diary format in the Azuma Kagami. It chronicled not only people’s lives and key events (with varying accuracy), but other daily observations, including the appearance of a new star.
“There are many accounts of this temporary guest star in historical records from Japan, China and Korea. At its peak, the star’s brightness was comparable to Saturn’s. It remained visible to the naked eye for about 180 days, until it gradually dimmed out of sight. The remnant of the SN 1181 explosion is now very old, so it is dark and difficult to find,” explained lead author Takatoshi Ko, a doctoral student from the Department of Astronomy at the University of Tokyo.
The remnant of this guest star, labeled supernova remnant (SNR) 1181, was found to have been created when two extremely dense, Earth-sized stars, called white dwarfs, collided. This created a rare type of supernova, called a Type Iax supernova, which left behind a single, bright and fast-rotating white dwarf. Aided by observations on its position noted in the historical document, modern astrophysicists finally pinpointed its location in 2021 in a nebula towards the constellation Cassiopeia.
Due to its rare nature and location within our galaxy, SNR 1181 has been the subject of much observational research. This suggested that SNR 1181 is made up of two shock regions, an outer region and an inner one. In this new study, the research group analyzed the latest X-ray data to construct a theoretical computer model to explain these observations, and which has recreated the previously unexplained structure of this supernova remnant.
The main challenge was that according to conventional understanding, when two white dwarfs collide like this, they should explode and disappear. However, this merger left behind a white dwarf. The spinning white dwarf was expected to create a stellar wind (a fast-flowing stream of particles) immediately after its formation. However, what the researchers found was something else.
“If the wind had started blowing immediately after SNR 1181’s formation, we couldn’t reproduce the observed size of the inner shock region,” said Ko. “However, by treating the wind’s onset time as variable, we succeeded in explaining all of the observed features of SNR 1181 accurately and unraveling the mysterious properties of this high-speed wind. We were also able to simultaneously track the time evolution of each shock region, using numerical calculations.”
The team was very surprised to find that according to their calculations, the wind may have started blowing only very recently, within the past 20-30 years. They suggest this may indicate that the white dwarf has started to burn again, possibly due to some of the matter thrown out by the explosion witnessed in 1181 falling back to its surface, increasing its density and temperature over a threshold to restart burning.
To validate their computer model, the team is now preparing to further observe SNR 1181 using the Very Large Array (VLA) radio telescope based in central New Mexico state in the U.S., and the 8.2 meter-class Subaru Telescope in the U.S. state of Hawaii.
“The ability to determine the age of supernova remnants or the brightness at the time of their explosion through archaeological perspectives is a rare and invaluable asset to modern astronomy,” said Ko. “Such interdisciplinary research is both exciting and highlights the immense potential for combining diverse fields to uncover new dimensions of astronomical phenomena.”
Comparison of X-ray image (left) and new schematic (right)
CAPTION
These images show the two shock regions of the remnant SNR 1181. The bright white at the center is the white dwarf.
CREDIT
2024 T. Ko, H. Suzuki, K. Kashiyama et al./ The Astrophysical Journal
Paper
Takatoshi Ko, Hiromasa Suzuki, Kazumi Kashiyama, Hiroyuki Uchida, Takaaki Tanaka, Daichi Tsuna, Kotaro Fujisawa, Aya Bamba and Toshikazu Shigeyama. A dynamical model for IRAS 00500+6713: the remnant of a type Iax supernova SN 1181 hosting a double degenerate merger product WD J005311. The Astrophysical Journal. 5th July, 2024 DOI: 10.3847/1538-4357/ad4d99
Funding:
This research has made use of data and software provided by the High Energy Astrophysics Science Archive Research Center (HEASARC), which is a service of the Astrophysics Science Division at NASA/GSFC. This work was financially supported by Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research (KAKENHI) Grant Numbers JP24KJ0672(TK), JP21J00031 (HS), JP24K00668 (KK), JP20K04010 (KK), JP20H01904 (KK), JP22H00130 (KK), JP22H01265 (HU), JP19H01936 (TT), JP21H04493 (TT), JP20K14512 (KF), JP23H01211 (AB), JP22K03688 (TS), JP22K03671 (TS), and JP20H05639 (TS). DT is supported by the Sherman Fairchild Postdoctoral Fellowship at the California Institute of Technology. TK is supported by RIKEN Junior Research Associate Program.
Conflicts of interest:
None
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JOURNAL
The Astrophysical Journal
METHOD OF RESEARCH
Computational simulation/modeling
ARTICLE TITLE
A dynamical model for IRAS 00500+6713: the remnant of a type Iax supernova SN 1181 hosting a double degenerate merger product WD J005311
ARTICLE PUBLICATION DATE
5-Jul-2024
"Motion picture" view of warped Milky Way reveals shape of its dark matter halo
CHINESE ACADEMY OF SCIENCES HEADQUARTERS
A research team led by Dr. HUANG Yang from the National Astronomical Observatories of the Chinese Academy of Sciences (NAOC) pioneered the "motion picture" method for measuring the precession rate of the Milky Way's disk warp. This method allows the clear observation of the precession direction and rate of the Milky Way's warp using a sample of Cepheid variable stars of different ages. Based on these measurements, the team revealed that the current dark matter halo of the Milky Way is slightly oblate. The study was published online in Nature Astronomy.
In the nearby universe, nearly one-third of disk galaxies are not perfect disks but exhibit a warped shape resembling a potato chip. Astronomers refer to this phenomenon as a disk warp. The Milky Way, as a typical disk galaxy, also has this warp feature. It is generally believed that the warp originates from the rotational plane of the outer disk stars deviating from the symmetry plane of the surrounding dark matter halo. This tilted, rotating Galactic disk, much like a spinning top, inevitably undergoes precession due to the torque exerted by the surrounding dark matter halo.
However, the measurement of this important dynamic parameter, both in direction and rate, has been widely debated. This is because previous measurements relied on indirect kinematic methods, where the tracers used are subject to dynamical perturbations or heating effects, greatly limiting their accuracy and precision.
This study used 2,600 young classical Cepheid variable stars discovered by Gaia as tracers, along with precise distance and age data from both Gaia and LAMOST. The researchers, using the "motion picture" method, constructed the three-dimensional structure of the Milky Way's disk across populations of various ages but all younger than 250 Myr.
By "seeing" how the disk warp evolves with age, the researchers found that the warp precesses in a retrograde direction at a rate of 2 km/s/kpc (or 0.12 degrees per million years).
Further measurements showed that the warp's precession rate gradually decreases with radius. Regardless of the origin of the warp, its precession rate and direction were jointly determined by the Galactic inner disk and the dark matter halo.
After subtracting the contribution of the Galactic inner disk, the researchers found that the current dark matter halo enveloping the warp exhibits a slightly oblate ellipsoidal shape with a flattening ratio q between 0.84 and 0.96 for the equipotential surfaces. Currently, only this shape can explain the remaining precession rate of the warp.
This study provides a crucial anchor point for studying the evolution of the Milky Way's dark matter halo.
JOURNAL
Nature Astronomy
ARTICLE TITLE
A slightly oblate dark matter halo revealed by a retrograde precessing Galactic disk warp
Searching for dark matter with the coldest quantum detectors in the world
IMAGE:
THE EXPERIMENT IS AT ABOUT A 10000TH OF A DEGREE ABOVE ABSOLUTE ZERO IN A SPECIAL REFRIGERATOR ; DR AUTTI (RIGHT)
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CREDIT: LANCASTER UNIVERSITY
One of the greatest mysteries of science could be one step closer to being solved.
Approximately 80% of the matter in the universe is dark, meaning that it cannot be seen. In fact, dark matter is passing through us constantly – possibly at a rate of trillions of particles per second.
We know it exists because we can see the effects of its gravity, but experiments to date have so far failed to detect it.
Taking advantage of the most advanced quantum technologies, scientists from Lancaster University, the University of Oxford, and Royal Holloway, University of London are building the most sensitive dark matter detectors to date.
Their public exhibit entitled “A Quantum View of the Invisible Universe” is showcased at this year’s Royal Society’s flagship Summer Science Exhibition from 2-7 July 2024.
The researchers include Dr Michael Thompson, Professor Edward Laird, Dr Dmitry Zmeev and Dr Samuli Autti from Lancaster, Professor Jocelyn Monroe from Oxford and Professor Andrew Casey from RHUL.
EPSRC Fellow Dr Autti said: “We are using quantum technologies at ultra-low temperatures to build the most sensitive detectors to date. The goal is to observe this mysterious matter directly in the laboratory and solve one of the greatest enigmas in science.”
There is indirect observational evidence of the typical dark matter density in the galaxy, but the mass of the constituent particles and their possible interactions with ordinary atoms are unknown.
Particle physics theory suggests two likely dark matter candidates: new particles with interactions so weak we haven’t observed them yet, and, very light wave-like particles termed axions. The team are building two experiments, one to search for each.
Of the two candidates, new particles with ultra-weak interactions could be detected through their collisions with ordinary matter. However, whether these collisions can be identified in an experiment depends on the mass of the dark matter being searched for. Most searches so far would be able to detect dark matter particles weighing between five and 1,000 times more than a hydrogen atom, but it is possible that much lighter dark matter candidates may have been missed.
The Quantum Enhanced Superfluid Technologies for Dark Matter and Cosmology (QUEST-DMC) team aims to reach world-leading sensitivity to collisions with dark matter candidates with mass between 0.01 to a few hydrogen atoms. To achieve this, the detector is made of superfluid helium-3, cooled into a macroscopic quantum state and instrumented with superconducting quantum amplifiers. Combining these two quantum technologies creates the sensitivity to measure extremely weak signatures of dark matter collisions.
By contrast, if dark matter is made from axions, they will be extremely light – more than a billion times lighter than a hydrogen atom – but correspondingly more abundant. Scientists would not be able to detect collisions with axions, but they can search instead for another signature - an electrical signal that results when axions decay in a magnetic field. This effect can only be measured using an exquisitely sensitive amplifier that works at the highest precision allowed by quantum mechanics. The Quantum Sensors for the Hidden Sector (QSHS) team is therefore developing a new class of quantum amplifier that is perfectly suited to search for an axion signal.
The stand at this year’s exhibition will enable visitors to observe the unseeable with imaginative hands-on exhibits for all ages.
Demonstrating how we infer dark matter from observing galaxies, there will be a gyroscope-in-a-box that moves in surprising ways due to the unseen angular momentum. There will also be glass marbles that are transparent in liquid, showing how invisible masses may be observed using clever experimentation.
A light-up dilution refrigerator will demonstrate how the team achieve ultra-low temperatures, and a model dark matter particle collision detector will show how our Universe would behave if dark matter behaved like normal matter.
Visitors can then search for dark matter with a model axion detector by scanning the frequency of a radio receiver, and they can also create their own parametric amplifier using a pendulum.
Cosmologist Carlos Frenk, Fellow of the Royal Society and Chair of the Public Engagement Committee, said: “Science is vital in helping us understand the world we live in – past, present and future. I urge visitors of all ages to come along with an open mind, curiosity and enthusiasm and celebrate incredible scientific achievements that are benefiting us all.”
The research in this exhibit is supported by the UKRI Quantum Technologies for Fundamental Physics programme.
