SPACE/COSMOS
Astronomers detect ancient lonely quasars with murky origins
The quasars appear to have few cosmic neighbors, raising questions about how they first emerged more than 13 billion years ago.
Massachusetts Institute of Technology
image:
This image, taken by NASA’s James Webb Space Telescope, shows an ancient quasar (circled in red) with fewer than expected neighboring galaxies (bright blobs), challenging physicists’ understanding of how the first quasars and supermassive black holes formed.
view moreCredit: Christina Eilers/EIGER team
A quasar is the extremely bright core of a galaxy that hosts an active supermassive black hole at its center. As the black hole draws in surrounding gas and dust, it blasts out an enormous amount of energy, making quasars some of the brightest objects in the universe. Quasars have been observed as early as a few hundred million years after the Big Bang, and it’s been a mystery as to how these objects could have grown so bright and massive in such a short amount of cosmic time.
Scientists have proposed that the earliest quasars sprang from overly dense regions of primordial matter, which would also have produced many smaller galaxies in the quasars’ environment. But in a new MIT-led study, astronomers observed some ancient quasars that appear to be surprisingly alone in the early universe.
The astronomers used NASA’s James Webb Space Telescope (JWST) to peer back in time, more than 13 billion years, to study the cosmic surroundings of five known ancient quasars. They found a surprising variety in their neighborhoods, or “quasar fields.” While some quasars reside in very crowded fields with more than 50 neighboring galaxies, as all models predict, the remaining quasars appear to drift in voids, with only a few stray galaxies in their vicinity.
These lonely quasars are challenging physicists’ understanding of how such luminous objects could have formed so early on in the universe, without a significant source of surrounding matter to fuel their black hole growth.
“Contrary to previous belief, we find on average, these quasars are not necessarily in those highest-density regions of the early universe. Some of them seem to be sitting in the middle of nowhere,” says Anna-Christina Eilers, assistant professor of physics at MIT. “It’s difficult to explain how these quasars could have grown so big if they appear to have nothing to feed from.”
There is a possibility that these quasars may not be as solitary as they appear, but are instead surrounded by galaxies that are heavily shrouded in dust and therefore hidden from view. Eilers and her colleagues hope to tune their observations to try and see through any such cosmic dust, in order to understand how quasars grew so big, so fast, in the early universe.
Eilers and her colleagues report their findings in a paper appearing today in the Astrophysical Journal. The MIT co-authors include postdocs Rohan Naidu and Minghao Yue; Robert Simcoe, the Francis Friedman Professor of Physics and director of MIT’s Kavli Institute for Astrophysics and Space Research; and collaborators from institutions including Leiden University, the University of California at Santa Barbara, ETH Zurich, and elsewhere.
Galactic neighbors
The five newly observed quasars are among the oldest quasars observed to date. More than 13 billion years old, the objects are thought to have formed between 600 to 700 million years after the Big Bang. The supermassive black holes powering the quasars are a billion times more massive than the sun, and more than a trillion times brighter. Due to their extreme luminosity, the light from each quasar is able to travel over the age of the universe, far enough to reach JWST’s highly sensitive detectors today.
“It’s just phenomenal that we now have a telescope that can capture light from 13 billion years ago in so much detail,” Eilers says. “For the first time, JWST enabled us to look at the environment of these quasars, where they grew up, and what their neighborhood was like.”
The team analyzed images of the five ancient quasars taken by JWST between August 2022 and June 2023. The observations of each quasar comprised multiple “mosaic” images, or partial views of the quasar’s field, which the team effectively stitched together to produce a complete picture of each quasar’s surrounding neighborhood.
The telescope also took measurements of light in multiple wavelengths across each quasar’s field, which the team then processed to determine whether a given object in the field was light from a neighboring galaxy, and how far a galaxy is from the much more luminous central quasar.
“We found that the only difference between these five quasars is that their environments look so different,” Eilers says. “For instance, one quasar has almost 50 galaxies around it, while another has just two. And both quasars are within the same size, volume, brightness, and time of the universe. That was really surprising to see.”
Growth spurts
The disparity in quasar fields introduces a kink in the standard picture of black hole growth and galaxy formation. According to physicists’ best understanding of how the first objects in the universe emerged, a cosmic web of dark matter should have set the course. Dark matter is an as-yet unknown form of matter that has no other interactions with its surroundings other than through gravity.
Shortly after the Big Bang, the early universe is thought to have formed filaments of dark matter that acted as a sort of gravitational road, attracting gas and dust along its tendrils. In overly dense regions of this web, matter would have accumulated to form more massive objects. And the brightest, most massive early objects, such as quasars, would have formed in the web’s highest-density regions, which would have also churned out many more, smaller galaxies.
“The cosmic web of dark matter is a solid prediction of our cosmological model of the Universe, and it can be described in detail using numerical simulations,” says co-author says Elia Pizzati, a graduate student at Leiden University. “By comparing our observations to these simulations, we can determine where in the cosmic web quasars are located.”
Scientists estimate that quasars would have had to grow continuously with very high accretion rates in order to reach the extreme mass and luminosities at the times that astronomers have observed them, fewer than 1 billion years after the Big Bang.
“The main question we’re trying to answer is, how do these billion-solar-mass black holes form at a time when the universe is still really, really young? It’s still in its infancy,” Eilers says.
The team’s findings may raise more questions than answers. The “lonely” quasars appear to live in relatively empty regions of space. If physicists’ cosmological models are correct, these barren regions signify very little dark matter, or starting material for brewing up stars and galaxies. How, then, did extremely bright and massive quasars come to be?
“Our results show that there’s still a significant piece of the puzzle missing of how these supermassive black holes grow,” Eilers says. “If there’s not enough material around for some quasars to be able to grow continuously, that means there must be some other way that they can grow, that we have yet to figure out.”
This research was supported, in part, by the European Research Council.
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Written by Jennifer Chu, MIT News
Paper: “EIGER VI. The Correlation Function, Host Halo Mass and Duty Cycle of Luminous Quasars at z & 6”
https://iopscience.iop.org/article/10.3847/1538-4357/ad778b
Article Title
“EIGER VI. The Correlation Function, Host Halo Mass and Duty Cycle of Luminous Quasars at z & 6”
Near-earth microquasar a source of powerful radiation
The Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences
image:
Sources of high-energy cosmic rays in the vicinity of the microquasar V4641 Sag, on the left with energies above a teraelectronvolt, on the right – hundreds of teraelectronvolts. The location of the microquasar is marked with a yellow dot.
view moreCredit: IFJ PAN / HAWC
Cracow, 17 October 2024 - Modern astronomy has clung to the belief that the relativistic outflows or jets responsible for the existence of electromagnetic radiation of particularly high energies are located in the nuclei of active galaxies distant from Earth. However, a different picture of reality is emerging from the latest data from the HAWC observatory: also jets launched in astrophysical sources from our own intra-galactic ‘backyard’ turn out to be sources of gamma photons of extremely high energy.
Electromagnetic radiation of extremely high energies is produced not only in the jets launched in active nuclei of distant galaxies, but also in jet-launching objects lying within the Milky Way, called microquasars. This latest finding by scientists from the international High-Altitude Water Cherenkov Gamma-Ray Observatory (HAWC) radically changes the previous understanding of the mechanisms responsible for the formation of ultra-high-energy cosmic radiation and in practice marks a revolution in its further study.
Since the discovery of cosmic radiation by Victor Hess in 1912, astronomers have believed that the celestial bodies responsible in our galaxy for the acceleration of these particles up to the highest energies are the remains of gigantic supernova explosions, called supernova remnants. However, a different picture is emerging from the latest data from the HAWC observatory: the sources of radiation of extremely high energies turn out to be microquasars. Astrophysicists from the Institute of Nuclear Physics of the Polish Academy of Sciences (IFJ PAN) in Cracow, co-financed by a grant from the National Science Centre, played a key role in the discovery.
The HAWC observatory was erected on the slope of the Sierra Negra volcano in Mexico with the aim of recording incoming particles and photons from space at particularly high energies. The facility consists of 300 steel water tanks equipped with photomultipliers sensitive to fleeting flashes of light, known as Cherenkov radiation. This appears in the tank when a particle travelling faster than the speed of light in water falls into it. Typically, the HAWC captures gamma photons with energies ranging from hundreds of gigaelectronvolts to hundreds of teraelectronvolts. These are energies up to a trillion times greater than the energy of visible light photons and over a dozen times greater than the energy of protons accelerated at the Large Hadronic Collider (LHC) accelerator.
The supermassive black holes within quasars, i.e. the active nuclei of some galaxies (objects with enormous masses, numbering in the hundreds of millions of solar masses) accelerate and absorb matter from the accretion disk that surrounds them. During this process, very narrow and very long streams of matter, called jets, are shot out from near the poles of the black hole, in both directions along its rotation axis. These move at velocities often close to the speed of light, resulting in shock waves – and it is there that photons of extremely high energies, reaching up to hundreds of teraelectronvolts, are produced.
Located in the nuclei of other galaxies, quasars are among objects that are very distant from us: the nearest (Markarian 231) is 600 million light years away from Earth. This is not the case for microquasars. These are compact binary systems, made up of a massive star and its matter-absorbing black hole, which emit jets with lengths of hundreds of light years. Several tens of such objects have so far been discovered in our galaxy alone.
“Photons detected from microquasars have usually much lower energies than those from the quasars. Usually, we are talking about values of the order of tens of gigaelectronvolts. Meanwhile, we have observed something quite incredible in the data recorded by the detectors of the HAWC observatory: photons coming from a microquasar lying in our galaxy and yet carrying energies tens of thousands of times higher than typical!” says Dr. Sabrina Casanova (IFJ PAN), who, together with Dr. Xiaojie Wang from Michigan Tech University and Dr. Dezhi Huang from University of Maryland were the first to observe the anomaly.
The source of photons with energies of up to 200 teraelectronvolts has been found to be the microquasar V4641 Sagittarii (V4641 Sgr). It lies in the background of the Sagittarius constellation, at a distance of about 20,000 light years from Earth. The main role here is played by a black hole with a mass of about six solar masses, pulling in matter from the stellar giant with a mass three times that of the Sun. The objects orbit around a common centre of mass, circling each other once in just under three days. Interestingly, the jet emitted by the V4641 Sgr system is directed towards the Solar System. In this configuration, an Earth-based observer has a relativistically distorted perception of the time of the matter at the beginning and end of the jet: its front begins to appear younger than it actually is. As a result, the jet seems to propagate through space at superluminal velocity, in the present case as much as nine times the speed of light.
“Significantly, the V4641 Sgr microquasar turns out not to be unique. Extremely energetic photons are meanwhile detected not only from this but also from other microquasars, detected by the LHAASO observatory. It therefore seems likely that microquasars significantly contribute to the cosmic ray radiation at the highest energies in our galaxy,” adds Dr. Casanova.
The latest discovery is of interest not only to cosmic ray scientists. It proves that at a relatively small distance from Earth, mechanisms of jet formation and production of ultra-energetic photons must be at work analogous to those in the nuclei of active, distant galaxies, scaled appropriately to the mass of the black hole. These processes in microquasars occur on a much more human-friendly timescale – over days, not hundreds of thousands or millions of years. Moreover, the photons emitted by microquasars do not have to make their way through the millions of light-years of the cosmic vacuum, where they can be scattered or absorbed during interactions with photons of the ubiquitous cosmic background radiation. All this means that astrophysicists have, for the first time, gained the ability to make comprehensive and virtually undisturbed observations of processes crucial to the evolution of galaxies.
The Henryk Niewodniczański Institute of Nuclear Physics (IFJ PAN) is currently one of the largest research institutes of the Polish Academy of Sciences. A wide range of research carried out at IFJ PAN covers basic and applied studies, from particle physics and astrophysics, through hadron physics, high-, medium-, and low-energy nuclear physics, condensed matter physics (including materials engineering), to various applications of nuclear physics in interdisciplinary research, covering medical physics, dosimetry, radiation and environmental biology, environmental protection, and other related disciplines. The average yearly publication output of IFJ PAN includes over 600 scientific papers in high-impact international journals. Each year the Institute hosts about 20 international and national scientific conferences. One of the most important facilities of the Institute is the Cyclotron Centre Bronowice (CCB), which is an infrastructure unique in Central Europe, serving as a clinical and research centre in the field of medical and nuclear physics. In addition, IFJ PAN runs four accredited research and measurement laboratories. IFJ PAN is a member of the Marian Smoluchowski Kraków Research Consortium: “Matter-Energy-Future”, which in the years 2012-2017 enjoyed the status of the Leading National Research Centre (KNOW) in physics. In 2017, the European Commission granted the Institute the HR Excellence in Research award. As a result of the categorization of the Ministry of Education and Science, the Institute has been classified into the A+ category (the highest scientific category in Poland) in the field of physical sciences.
CONTACTS:
Dr. Sabrina Casanova
Institute of Nuclear Physics, Polish Academy of Sciences
tel.: +48 12 6628274
email: sabrina.casanova@ifj.edu.pl
SCIENTIFIC PUBLICATIONS:
“Ultra-high-energy gamma-ray bubble around microquasar V4641 Sgr”
HAWC Collaboration
Nature 2024, 634, 557-560
DOI: 10.1038/s41586-024-07995-9
LINKS:
The website of the Institute of Nuclear Physics, Polish Academy of Sciences.
Press releases of the Institute of Nuclear Physics, Polish Academy of Sciences.
IMAGES:
IFJ241017b_fot01s.jpg
HR: http://press.ifj.edu.pl/news/2024/10/17/IFJ241017b_fot01.jpg
Sources of high-energy cosmic rays in the vicinity of the microquasar V4641 Sag, on the left with energies above a teraelectronvolt, on the right – hundreds of teraelectronvolts. The location of the microquasar is marked with a yellow dot. (Source: IFJ PAN / HAWC)
Journal
Nature
Article Title
Ultra-high-energy gamma-ray bubble around microquasar V4641 Sgr
Article Publication Date
16-Oct-2024
Astrobiology: Potential microbial habitats in Martian ice
Springer
Dusty ice exposed at the surface of Mars could provide the conditions necessary for the presence of photosynthetic life, according to a modelling study. The findings, published in Communications Earth & Environment, suggest that ice deposits located in the planet’s mid-latitudes should be a key location in any search for life on Mars.
High levels of harmful ultraviolet radiation from the Sun make current life on the surface of Mars almost certainly impossible. However, a sufficiently thick layer of ice can absorb this radiation and could protect cells living below its surface. Any life in these conditions would need to be in a so-called radiative habitable zone — shallow enough to receive enough visible light for photosynthesis, but deep enough to be protected from the ultraviolet radiation.
Aditya Khuller and colleagues calculated whether such a radiative habitable zone could exist in ice with the dust content level and structure of the ice observed on Mars. They found that very dusty ice would block too much sunlight, but that in ice containing 0.01–0.1% dust, a habitable region could potentially exist at depths between 5 and 38 centimetres (depending on the size and purity of the ice crystals). In cleaner ice, a larger habitable zone could exist between 2.15 and 3.10 metres deep. The authors explain that dust particles within the ice could cause occasional localised melting at depths of up to approximately 1.5 metres, providing the liquid water necessary for any photosynthetic life to survive. They suggest that the polar regions on Mars would be too cold for this process, but that subsurface melting could occur in mid-latitude areas (between approximately 30 and 50 degrees latitude).
The authors caution that the potential existence of theoretically habitable zones does not mean that photosynthetic life is, or has ever been, present on Mars. However, it does suggest that the few instances of exposed ice in the Martian mid-latitudes could be key areas for future searches for life to focus on.
Journal
Communications Earth & Environment
Method of Research
Computational simulation/modeling
Subject of Research
Not applicable
Article Title
Potential for photosynthesis on Mars within snow and ice
Article Publication Date
17-Oct-2024
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