An international team of paleontologists from Romania, Hungary and Italy has identified a new genus and species of herbivorous, duck-billed dinosaur from an incomplete skeleton unearthed in the Hațeg Basin, a bowl-shaped depression in the Carpathians of present-day Romania.
The post New Duck-Billed Dinosaur Unearthed in Romania appeared first on Sci.News: Breaking Science News.
In the complex landscape of brain development, the formation of the brain’s protective barriers—the blood-brain barrier (BBB) and the blood-cerebrospinal fluid (CSF) barrier—has long fascinated neuroscientists. These barriers are composed of highly specialized cells that serve a critical function: permitting necessary nutrients to enter the brain while preventing harmful substances, pathogens, and toxins circulating in the bloodstream from crossing into the delicate neural environment. Despite a deep understanding of their function, the cellular mechanisms orchestrating their assembly during embryogenesis have remained elusive. A groundbreaking study led by researchers at the University of California San Diego, recently published in Cell, unveils a surprising and paradigm-shifting contributor to brain barrier development: cellular senescence.
Cellular senescence is traditionally characterized as a permanent cessation of cell division, commonly associated with aging and pathology. These so-called “zombie” cells, which remain metabolically active but fail to proliferate, accumulate in aging tissues, contributing to chronic inflammation, tissue dysfunction, and cognitive decline. As a consequence, senescent cells have become key targets in developing therapeutic strategies to mitigate age-related diseases. However, recent evidence challenges the simplistic association of senescence solely with aging and damage. Instead, senescence appears highly context-dependent, playing complex and sometimes beneficial roles in development and healing.
Emerging studies have revealed transient senescent cell populations in mouse embryos during the formation of limbs and kidneys, as well as in wound healing contexts, where senescence promotes tissue repair. These discoveries suggest that senescence may be an evolutionarily conserved mechanism to guide tissue remodeling and regeneration when temporally controlled. The UC San Diego research team, led by Assistant Professor Hiruy Meharena, has extended this concept into the realm of brain development, uncovering diverse senescence-associated cell states that actively contribute to constructing the brain’s vital protective barriers.
Through a multifaceted approach combining single-cell RNA sequencing, advanced imaging, and precise genetic lineage tracing in developing mouse brains, the investigators identified three distinct cell types that transiently or persistently enter senescence during the formation of the BBB and blood-CSF barrier. These cell types include vascular endothelial cells, brain-resident macrophages, and choroid plexus epithelial cells, each exhibiting unique senescence profiles and functional roles in the brain’s developmental timeline.
Vascular endothelial cells, which line the embryonic blood vessels, and brain-resident macrophages engage senescence transiently during critical windows of brain vascular remodeling and patterning. These senescent states appear to fine-tune the formation of the intricate vascular network essential for establishing the highly selective BBB, coordinating cellular interactions and molecular signaling pathways that regulate tight junction formation and barrier integrity. This temporary senescent phase helps orchestrate the vascular architecture that prevents harmful molecules in the blood from infiltrating brain tissue.
In contrast, choroid plexus epithelial cells—responsible for generating cerebrospinal fluid and forming the blood-CSF barrier—exhibit a persistent senescence-like state that endures beyond embryonic development into adulthood. This finding defies the prevailing dogma that developmental senescence is exclusively transient and suggests a novel dimension of senescence’s role in maintaining barrier function over the lifespan. The sustained senescent phenotype in these epithelial cells likely supports the continuous protective and homeostatic functions of the blood-CSF barrier, which plays a critical role in brain fluid regulation and immune surveillance.
One of the study’s most unexpected revelations emerged when the researchers experimentally ablated senescent cells during embryogenesis. The resulting mice exhibited marked abnormalities in the structural and functional development of both brain barriers, accompanied by disrupted fluid balance within the central nervous system. These defects underscore the indispensability of senescent cells in normal brain barrier formation and highlight the complex interplay between senescence and tissue morphogenesis.
This nuanced view of senescence challenges the traditional perception of a monolithic, detrimental “senescence program,” revealing instead a spectrum of senescence-associated cell states tailored to specific developmental contexts and cell types. Senescence acts not as a simple arrest signal but as a dynamic, multifaceted process facilitating intercellular cooperation during neurovascular development. It integrates molecular cues that modulate cell behavior, extracellular matrix remodeling, and immune cell function to sculpt the brain’s defensive frontiers.
The implications of these findings extend beyond developmental biology into the pathophysiology of brain disorders. Since the integrity of the BBB and blood-CSF barrier is compromised in neurodegenerative diseases, stroke, and neuroinflammation, understanding the diverse roles of senescent cells in barrier biology may herald new therapeutic avenues for restoring barrier function and mitigating neurological deficits. The UC San Diego team is now probing how senescence-related mechanisms unfold in disease contexts, aiming to decipher whether modulating senescent cell populations can ameliorate or prevent barrier dysfunction.
Moreover, the identification of persistent senescence in adult choroid plexus cells prompts intriguing questions about the balance between beneficial senescence and potential chronic senescent cell accumulation contributing to pathology. Future research will explore how this persistent senescence is regulated and whether it participates in age-related changes in brain fluid dynamics or susceptibility to CNS infections.
This research challenges the classical narrative that equates senescence with detrimental aging by elucidating its fundamental, constructive roles in brain development. It elevates the concept of senescence from a pathological endpoint to an essential, adaptive cellular state finely tuned in time and space. By redefining senescence as a developmental and homeostatic facilitator, the study sets a new trajectory for investigating cellular aging, brain barrier biology, and neurovascular health.
As neuroscience embraces the complexity of cellular states within the brain’s microenvironment, these insights offer a richer, more integrative framework. The study’s comprehensive use of cutting-edge genomic, imaging, and genetic tools exemplifies the power of modern neurobiology to unravel the elusive choreography underlying brain structure and function. Continued exploration of developmental senescence promises to deepen our understanding of brain physiology and opens transformative possibilities for innovative treatments targeting the blood-brain and blood-CSF barriers across the lifespan.
Subject of Research: Animals
Article Title: Persistent and transient senescent cells contribute to brain barrier development
News Publication Date: 10-Jun-2026
Web References: https://www.cell.com/cell/fulltext/S0092-8674(26)00581-7
References: DOI 10.1016/j.cell.2026.05.022
Image Credits: Ella Maru Studio, conceptualized by Ashley Watson and Hiruy Meharena
Keywords: Cellular neuroscience, cellular senescence, developmental neuroscience, molecular neuroscience, cellular physiology, cell development, cellular processes
In the quest to unlock new frontiers in chemical synthesis, researchers are persistently searching for innovative methods that allow the formation and manipulation of molecular bonds in unprecedented ways. A remarkable breakthrough has emerged from the laboratory of Professor Yang Yang at the University of California, Santa Barbara, where his team has pioneered a novel class of biocatalytic reactions that blend the power of enzymatic catalysis with advances in photochemistry. This groundbreaking research, recently published in the prestigious journal Nature Catalysis, reveals a previously unknown mechanism for carbon-carbon bond formation via metal-carbene chemistry, fundamentally expanding the toolkit available to chemists for building complex molecules.
Transition metal carbene chemistry has been a vibrant area of study for decades, owing to the unique reactivity of metal-carbene intermediates—transient species in which a metal center is bound to a divalent carbon atom. These metal-carbenes act as powerful but fleeting intermediates, able to forge key carbon-carbon bonds essential for constructing the diverse frameworks found in pharmaceuticals, agrochemicals, and advanced materials. Despite their importance, the mechanistic landscape of metal-carbene chemistry remained relatively constrained, with well-established pathways that have been refined but seldom revolutionized—until now.
Professor Yang’s innovative approach combines two distinct catalytic cycles working in synergy: a light-driven photoredox cycle and an enzymatic metalloenzyme catalytic cycle. This integration ushers in a new paradigm where photochemically generated radical intermediates are directly coupled with enzymatically created iron-carbenoid intermediates. This union facilitates an intermolecular carbon-carbon bond-forming reaction that exploits radical intermediates in a controlled enzymatic environment—an achievement that not only challenges existing dogmas but also heralds unprecedented control over reaction selectivity and efficiency.
Central to this discovery is the use of directed evolution to engineer a metalloprotein catalyst capable of hosting iron ions within its active site. This finely tuned protein environment not only produces the iron-carbenoid intermediate but also exercises exquisite control over the highly reactive iron-radical intermediates generated during the photochemical step. The enzyme facilitates the crucial proton transfer step, a fundamental transformation in organic synthesis, with a precision that synthetic catalysts have struggled to match. Without this engineered metalloenzyme, the researchers believe this distinctive chemistry would have likely remained undisclosed.
The cooperation between photoredox catalysis and metalloenzyme activity effectively pushes the boundaries of transition metal carbene chemistry, offering a synthetic strategy with considerable generality. The dual catalytic system provides a versatile platform for carbon-carbon bond formation, accommodating a broad range of substrates and enabling the construction of molecules featuring multiple stereogenic centers. Such stereochemical complexity is vital for function in biologically active compounds, underscoring the potential impact on drug discovery and the design of agrochemical agents.
Photoredox catalysis has garnered significant attention in recent years for its ability to harness visible light energy to access radical intermediates under mild conditions. By integrating this with a metalloenzyme cycle, Yang’s team has pioneered a cooperative catalytic process that allows controlled radical coupling in a biological setting, effectively marrying the finesse of enzymatic catalysis with the versatility of photochemistry. This represents a new frontier in synthetic methodology, where light-powered biocatalysts can orchestrate complex chemical transformations with enhanced selectivity and sustainability.
The intricate mechanistic interplay revealed through this work demonstrates how radicals—often regarded as indiscriminate and challenging to control—can be tamed within an enzymatic pocket. The iron center in the metalloenzyme acts as a conductor, directing the radical pathway toward selective bond formation, while the protein scaffold stabilizes ephemeral intermediates. This fine balance of reactivity and control is unprecedented in the realm of metallocarbene chemistry and exemplifies the power of directed evolution in tailoring enzyme function for synthetic purposes.
Beyond method development, the researchers anticipate a wide spectrum of applications that could flow from this approach. The ability to generate complex, chiral molecules with high precision opens doors for the synthesis of fine chemicals and bioactive compounds that were previously difficult or impractical to obtain. Moreover, the modularity of this dual catalytic platform suggests that it could be expanded to include other metal centers and reaction types, fostering a versatile toolkit adaptable to diverse chemical challenges.
The collaborative nature of this research, involving experts from UCSB, the University of Pittsburgh, and Florida State University, highlights the interdisciplinary effort required to unravel such complex chemistry. Combining expertise in enzymology, photoredox catalysis, organometallic chemistry, and computational modeling was crucial in elucidating the mechanism and optimizing the catalytic system. This synergy underlines the importance of collaborative approaches in pushing the boundaries of contemporary chemical science.
Moving forward, the team plans to generalize this transformative methodology to broaden its applicability. By exploring additional substrates and refining the biocatalyst through further rounds of directed evolution, they aim to generate a diverse array of synthetically valuable molecules. This work not only deepens fundamental mechanistic understanding but also provides a roadmap for integrating photochemical activation with biocatalysis, opening avenues for green and sustainable synthesis.
In summary, the discovery of this new metal-carbene chemistry mechanism represents a significant leap in transition metal catalysis. It leverages the specificity and tunability of metalloenzymes engineered by directed evolution, combined with the power of photochemistry, to orchestrate complex carbon-carbon bond-forming reactions with unprecedented control. This advancement is poised to transform the synthesis of stereochemically rich molecules critical to pharmaceuticals and agrochemicals, catalyzing further innovation in both academic and industrial chemistry.
Subject of Research: Novel metal-carbene biocatalytic reactions enabling carbon-carbon bond formation through integrated photoredox and metalloenzyme catalysis.
Article Title: (Information not provided)
News Publication Date: (Information not provided)
Web References:
References: Research by Yang’s lab including Huanan Wang, Chongtao Li, Xiao-Wang Chen at UCSB; Peng Liu and Binh Khanh Mai at the University of Pittsburgh; Rachel Weiss and Bryan Kudisch at Florida State University.
Image Credits: (Information not provided)
Physical sciences, Chemistry, Chemical reactions, Organic chemistry, Organometallic chemistry, Stereochemistry
In a groundbreaking study poised to reshape our understanding of Earth’s deep interior dynamics, researchers have unveiled a comprehensive model elucidating the genesis of the extensive large igneous provinces (LIPs) in the Pacific Ocean during the Early Cretaceous period. These massive volcanic events, which left a profound imprint on the planet’s geological record, had long been attributed to various causes including isolated mantle plumes, tectonic slab return flows, or complex plume–ridge interactions. This latest research integrates geophysical modeling with paleogeographic data to reveal a multifaceted interplay between mantle convection processes, subducting tectonic plates, and migrating mid-ocean ridges that collectively controlled the timing, location, and intensity of LIP formation.
The Pacific Ocean’s Early Cretaceous LIPs, encompassing some of the largest volcanic eruptions in Earth’s recent history, had puzzled researchers due to their sporadic yet intense episodes of basaltic outpourings. Historically, hypotheses have swung between attributing these vast eruptions to the arrival of deep superplumes—a concept suggesting stable, buoyant columns of hot mantle material rising from the core-mantle boundary—to mechanisms involving return flows of cold slabs being subducted beneath the Pacific basin. Adding complexity, the interaction between these mantle upwellings with tectonic spreading ridges has also been proposed as a trigger for massive melt generation. Yet, until now, a unified mechanistic explanation that could integrate these disparate phenomena remained elusive.
The pivotal insight of the new study comes from advanced mantle flow simulations constrained by precise paleogeographic reconstructions of Early Cretaceous plate configurations. By projecting plate motions and subduction geometries back in time, the researchers were able to create dynamic models of mantle convection patterns beneath the Pacific basin. These simulations revealed a stable pattern of thermally buoyant mantle upwellings, or plumes, persisting between approximately 165 million and 80 million years ago. Intriguingly, these upwellings were not isolated features but were rooted above enduring lower mantle thermal anomalies, suggesting the importance of inherited mantle structure in shaping convective behavior.
A particularly striking finding emerged around 130 to 125 million years ago, when the intensity of mantle upwelling reached its zenith. This peak activity appears fundamentally linked to an increase in slab flux beneath the Pacific realm, where enhanced subduction rates delivered cold tectonic plates deeply into the mantle, inducing a return flow that effectively strengthened the buoyant upwellings. This coupling indicates that rather than being independent processes, subduction dynamics and preexisting mantle heterogeneities synergistically elevate mantle temperatures and buoyancy, fostering conditions ripe for extensive melting and volcanic activity.
The study highlights the critical role of mantle-ridge interaction in modulating LIP genesis. Around 145 to 120 million years ago, migrating spreading ridges—regions where tectonic plates diverge, allowing mantle material to rise and solidify as new crust—passed over these vigorous upwellings. The models suggest that when spreading ridges intersected with zones of intense heat advection from the underlying mantle plumes, the accompanying thermal anomaly slowed ridge propagation. This transient deceleration enhanced the efficiency of mantle melting, channeling voluminous magma to Earth’s surface and triggering the prolific LIP eruptions witnessed in the geological record.
However, subsequent to this period of intense volcanic activity, the simulations indicate a pronounced decline in LIP eruption frequency and magnitude. This downturn corresponds to a combination of factors: a weakening of mantle upwelling intensity as slab flux diminishes, and the accelerated migration of spreading ridges away from the central Pacific mantle plumes. Such dynamic decoupling reduces the capacity for significant mantle melting beneath the ridges, thereby suppressing the generation of large-scale igneous provinces.
The revelations of this study carry profound implications for our grasp of Earth’s mantle convection and its surface expressions. The joint control of radial heat advection by slab flux and inherited lower-mantle structures innovatively bridges the gap between mantle plume theory and plate tectonic processes. It underscores the necessity of considering the deep Earth’s thermal architecture not as static but as an evolving, inherited template that interacts intricately with episodic tectonic phenomena to produce massive surface volcanism.
Moreover, the research offers a nuanced perspective on the temporal and spatial variability of LIP occurrences. The inferred stability of the central Pacific mantle upwellings over tens of millions of years challenges the traditional view that mantle plumes are transient or short-lived. Instead, the presence of deep-rooted thermal anomalies suggests longevity that serves as a backdrop for dynamic tectonic events, providing fertile mantle heat reservoirs that can be tapped repeatedly under favorable conditions.
The evidence for spreading ridges acting as crucial melting amplifiers rather than mere passive features reshapes existing paradigms around mid-ocean ridge evolution. The transient slowing of ridge migration due to underlying thermal anomalies offers a novel mechanism explaining how mantle melting can be efficiently modulated over geological timescales. This insight emphasizes the interconnectedness of deep mantle processes and plate boundary dynamics, illuminating a feedback system where surface plate motions influence, and are influenced by, mantle convection.
Such a feedback mechanism further accounts for the spatial clustering and episodic nature of LIP eruptions in the Pacific basin. As spreading ridges move relative to mantle plumes, the precise location and intensity of melting episodes shift, giving rise to spatially focused volcanic provinces at certain intervals. This dynamic explains observed geological distributions that earlier models struggled to fully capture, providing a cohesive narrative linking mantle physics, tectonic processes, and surface volcanism.
In addition to unraveling long-standing geological puzzles, this study also enhances predictive frameworks that may be vital for understanding the Earth’s future geodynamic behavior. The coupling between slab dynamics, mantle structure, and ridge migration suggests that monitoring contemporary subduction zones and spreading ridges could illuminate potential sites of enhanced mantle melting, which could, in extreme cases, relate to future volcanic hazards or crustal growth episodes.
The sophisticated modeling approaches employed further demonstrate the power of integrating multi-disciplinary datasets in geosciences. The confluence of plate reconstructions, mantle convection simulations, and thermal structure analyses exemplifies a holistic methodology transcending traditional disciplinary boundaries. This approach not only advances fundamental scientific knowledge but also opens avenues for exploration into Earth’s deep processes that underpin surface phenomena critical to the planet’s evolution.
While the findings present a compelling mechanism for Early Cretaceous LIP activity in the Pacific, the study also raises exciting questions about the potential for analogous mantle-plume and ridge interactions in other oceanic basins and geological epochs. Could similar dynamics explain volcanic provinces elsewhere, or are these processes unique to the Pacific’s mantle and tectonic configuration during that period? Future research targeted at extending these models globally and temporally promises to deepen our understanding of Earth’s geodynamic engine.
In conclusion, the fusion of mantle convection modeling with tectonic and paleogeographic data in this research provides a transformative lens on one of Earth’s most dramatic volcanic phenomena. The identification of vigorous mantle convection driven by tiered slab flux and legacy mantle structures, alongside nuanced ridge-upwelling interactions, charts a paradigm shift in interpreting large igneous province formation. These revelations not only solve longstanding enigmas of the Cretaceous Pacific LIPs but also refine the broader framework within which mantle dynamics and surface tectonics coalesce to sculpt our planet’s geological evolution.
As our planet continues to evolve, studies like this reaffirm the deep interconnectivity of processes spanning from Earth’s core to its crust, reminding us of the subtly intertwined forces shaping the planet on scales across both space and time. Through sophisticated simulations and integrative science, the tantalizing mysteries of Earth’s volcanic past inch closer to clarity, offering unprecedented glimpses into the fiery heart of our dynamic planet.
Subject of Research: Mantle convection dynamics and formation of large igneous provinces during the Early Cretaceous period in the Pacific Ocean.
Article Title: Vigorous mantle convection triggered the Cretaceous Pacific large igneous provinces.
Article References:
Deng, D., Li, S., Cao, X. et al. Vigorous mantle convection triggered the Cretaceous Pacific large igneous provinces. Nat. Geosci. (2026). https://doi.org/10.1038/s41561-026-02016-y
Image Credits: AI Generated
Millions of homes are at risk from climate change, the British Geological Survey has claimed in a new report – but it relies on the IPCC's discredited RCP8.5 modelling, says Paul Homewood.
The post Millions of Homes at Risk from Climate Change, Claims British Geological Survey in New Report Relying on Discredited Modelling appeared first on The Daily Sceptic.
The James Webb Space Telescope (JWST) has revealed a cosmic catastrophe, as winds extinguished a star-forming galaxy in the early universe, offering new insight into earlier strange observations.
Cosmic winds may destroy entire galaxies, according to new JWST research exploring the lingering mystery of why certain parts of the universe are unexpectedly devoid of growth.
The findings were published in a recent paper in the Monthly Notices of the Royal Astronomical Society, revealing galactic-scale death in a universe just one billion years old, and potentially answering questions about previous troubling JWST observations.
Observations made by the JWST revealed cold gas, an essential star-forming material, blowing out of the CRISTAL-2 galaxy in a massive plume, severely degrading its ability to produce new stars. According to the researchers, it would take less than 50 million years for the galaxy to be completely dead if this activity keeps up, a mere blink in the scheme of a 13.8 billion-year-old universe.
Astronomers consider galaxies to be “dead” if they are no longer capable of producing fresh stars. Traditionally, astronomers expected that it would take billions of years for an old galaxy to slowly run out of fuel and burn out. However, JWST observations have continually captured events in the early universe that were not expected to occur until much later.
One of these was finding a host of dead galaxies in the early universe shortly after it first became operational in 2022. How galaxies could die so close to the beginning of the universe, without sufficient time to burn through their cold gas supplies, has long perplexed scientists.
As researchers began considering various explanations for the phenomenon, they initially settled on dark energy, essentially explaining one unknown with another. Dark energy is a theoretical substance that scientists believe drives the expansion of the universe and was once a stronger force than it is now. While the Dark Energy Spectroscopic Instrument survey revealed last year that dark energy appears to be weakening over time, an exotic galaxy-killer is not required, according to this latest research.
Instead, researchers offer a much simpler explanation of powerful cosmic winds in the remote past. Conventional thinking has it that such powerful winds could only be generated by a supermassive black hole, yet these new observations challenge that assumption.
CRISTAL-02 is a galaxy still in the making, composed of several smaller galaxies in the final stages of merging into a single system. Because the early universe was far denser than it is today, such collisions were much more common. During these mergers, gravitational forces funnel vast amounts of gas toward the galactic centers, triggering intense bursts of star formation.
Observations of CRISTAL-02 by the James Webb Space Telescope and the Atacama Large Millimeter/submillimeter Array (ALMA) revealed a star formation rate roughly twice that of similar galaxies. Ironically, this extraordinary burst of stellar activity is also generating a powerful cosmic wind that is stripping away the very gas needed to form new stars.
Compounding the effect, many of the newly formed stars rapidly exhaust their fuel and end their lives as supernovae, producing additional outflows that further deplete the galaxy’s star-forming material.
Together, these processes appear capable of shutting down star formation far more quickly than astronomers previously believed possible. Going forward, ongoing JWST observations are likely to continue challenging astronomers’ assumptions, as more evidence indicates that nearly half of the early universe’s massive galaxies were interacting—a finding which also suggests early “galactic deaths” like these may not be all that rare, after all.
The paper, “Multiphase Images of a Powerful Supernova-Driven Wind in the Early Universe,” appeared in Monthly Notices of the Royal Astronomical Society on June 10, 2026.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.
A 12 year-old girl dubbed 'Sophie of Dundee' who was arrested after police initially believed a Bulgarian man's claims that she had called him a "f**ing migrant" has been vindicated after he was found guilty of assault.
The post 12 Year-Old ‘Sophie of Dundee’ Who Was Vilified and Arrested on Word of Bulgarian Man is Vindicated as He is Found Guilty of Assault appeared first on The Daily Sceptic.
Paleontologists have identified a new species of meiolaniform turtle from northern Patagonia, Argentina, that lived during the Maastrichtian age, just before the asteroid-triggered mass extinction that wiped out all non-avian dinosaurs.
The post Fossil Discovery in Patagonia Reveals New Species of Horned Turtle appeared first on Sci.News: Breaking Science News.
Google held at least 34 meetings with top German government officials – including the Chancellor – to discuss suppressing "hate speech" and "disinformation" online, reveals John Rosenthal.
The post Google Met Top German Government Officials Dozens of Times to Discuss Online “Hate Speech” and “Disinformation” appeared first on The Daily Sceptic.
Each Jupiter-size planet in the galaxy falls into one of three distinct categories: hot, warm, or cold. A new study suggests that despite the apparent differences between these populations, they may have all formed from the same underlying dynamical process: a game of pool played at planetary scales.
Though our solar system has only one Jupiter-size planet, elsewhere in the galaxy we have found three different species of these massive gas giants. Cold Jupiters closely resemble their namesake and orbit far from their host stars; hot Jupiters are the opposite and are found whipping around their stars on extremely close-in orbits. In between these are the warm Jupiters, which tend to orbit in the intermediate space between 0.1 and 1.0 au.
An artist’s depiction of a hot Jupiter. These planets orbit extremely close to their host stars, but likely got to their locations by scattering inward from more distant orbits. [NASA/JPL-Caltech]
Given these differences, it’s often thought that each of these populations arrived at its current location through different dynamical processes and that the history of the warm Jupiters is likely quite different from the history of the hot Jupiters. However, a new study led by Julia Esposito (Georgia Institute of Technology) has proposed an alternative view. Maybe these populations, though they appear different now, were all created by the same process: planet–planet scattering.
A schematic showing where different planets ended up as a function of where they scattered from during their evolution. Click to enlarge. [Esposito et al. 2026]
At the end of the simulation, the team surveyed the digital carnage. Almost every virtual system ended with only two planets after either ejecting one away from the star or having two planets collide. But, remarkably, the remaining two-planet systems looked tantalizingly similar to what we actually observe, with a mix of hot, warm, and cold Jupiters. Even more exciting, the end populations were highly correlated to where the violent scattering event took place.
For example, the warm Jupiters were almost all produced by “warm scattering” simulations, where the scattering took place between 0.1 and 1.0 au. The planets that survived the simulations and ended up as warm Jupiters matched all of the properties of the real warm Jupiter population: they had nearby companions, were moderately eccentric, and were mostly aligned with their stars. The hot Jupiters, meanwhile, were almost all produced by “cold scattering” events where the flybys happened far from the star and resulted in one planet hurtling inwards. These also matched all of the observed properties of real hot Jupiters.
The researchers concluded that planet–planet scattering can produce both the warm and hot Jupiter populations so long as you let the planets scatter from a variety of different distances. This exciting theoretical insight, if correct, would mean that astronomers could stop searching for different pathways to create each population. Happily, this model also provides testable predictions, and the authors lay out how the theory could be supported or disproven with additional data. Through virtual experiments like these, astronomers continue to build up an understanding of how the wide range of planetary architectures observed across the galaxy came to be.
“Unified Formation Channel of Hot and Warm Jupiters via Planet–Planet Scattering,” Julia Esposito et al 2026 ApJL 1003 L3. doi:10.3847/2041-8213/ae61b0
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How do massive galaxies form and evolve? A recent study traces the stellar and dust distributions across evolutionary phases of massive galaxies to better understand how massive dusty star-forming galaxies fit into the picture.
Massive galaxies, like the Milky Way or even larger, undergo phases of active star formation and quiescent phases of inactivity, but exactly how these galaxies evolve through these stages is not yet fully understood. Dusty star-forming galaxies, which are undergoing a period of intense star formation and shrouded in dust, might be the missing evolutionary step between star-forming and quiescent phases of massive galaxy evolution.
Currently, the leading explanation for massive galaxy formation and evolution is inside-out growth — star formation and quenching start in the inner regions of a galaxy and progress outward. However, it’s not clear whether dusty star-forming galaxies also follow the favored inside-out pathway, or if they instead proceed outside-in, first growing their disks and then assembling a central bulge.
Example of JWST NIRCam images with ALMA contour lines overlaid for select dusty star-forming galaxies in the sample. [Modified from Bodansky et al 2026]
To directly compare the star and dust morphologies across massive galaxies, Sarah Bodansky (University of Massachusetts, Amherst) and collaborators selected a sample of 33 dusty star-forming galaxies from the GOODS-ALMA 2.0 survey that searched the sky for 1.1-mm dust emission as well as star-forming and quiescent comparison samples drawn from JWST observations. Combining the ALMA survey data with JWST imaging, the authors studied the rest-frame optical (stars) and rest-frame near-infrared (dust) morphologies of dusty, star-forming, and quiescent galaxies at redshifts around cosmic noon (a few billion years after the Big Bang).
When comparing optical morphologies, the authors found that dusty star-forming galaxies and typical star-forming galaxies had similar distributions, but their near-infrared morphologies showed clear differences. Dusty galaxies tended to show more compact near-infrared emission, with dust tracing their stellar populations and more concentrated in the galaxies’ central regions. Though clearly different from star-forming galaxies, the authors noted striking similarities between the near-infrared morphologies of the dusty star-forming and quiescent galaxies, especially within their centers.
Average surface brightness profiles for the rest-optical (left) and rest-near-infrared (right) for the dusty (black), star-forming (blue), and quiescent (red) galaxies. In the near-infrared, the dusty star-forming galaxy profile appears very similar to the quiescent galaxy profile. [Bodansky et al 2026]
“JWST+ALMA Reveal the Buildup of Stellar Mass in the Cores of Dusty Star-forming Galaxies at Cosmic Noon,” Sarah Bodansky et al 2026 ApJ 1001 235. doi:10.3847/1538-4357/ae4f64
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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.
Title: Metal-Poor Star-Forming Clumps in Cosmic Noon Galaxies: Evidence for Gas Inflow and Chemical Dilution Using JWST NIRISS
Authors: Vicente Estrada-Carpenter et al.
First Author’s Institution: Arizona State University
Status: Published in ApJ
If you want to reconstruct a galaxy’s life story, one of the best “fossil records” is its metallicity. In astronomy this refers to the abundance of elements heavier than helium, which are made in stars and returned to a galaxy’s gas through winds and supernovae. Over time, more star formation usually means more metals mixed into the gas.
Now zoom to Cosmic Noon (roughly when the universe was most actively forming stars). Many galaxies in this epoch look “clumpy”; their star formation is concentrated in several bright knots scattered across the disk. The big question is where those clumps come from. Do they form from the galaxy’s own gas via internal disk instabilities, or do they light up when fresh, metal-poor gas flows in and both fuels star formation and dilutes the local metallicity?
The authors try to answer that question with JWST by measuring the metallicity of each clump relative to its immediate surroundings, rather than comparing clumps to a single galaxy-wide number (which can be misleading if the galaxy has a metallicity gradient).
They use JWST/Near Infrared Imager and Slitless Spectrograph (NIRISS) slitless grism spectroscopy from the CAnadian NIRISS Unbiased Cluster Survey (CANUCS) to study 20 lensed galaxies at redshift 0.6 < z < 1.35. (Lensing effectively acts like a zoom lens, helping to resolve smaller structures.) They focus on emission lines that trace star-forming gas, especially Hα (a star formation tracer) and sulfur lines [SII] and [SIII] (needed for their metallicity method).
Slitless spectra come with a headache: because there is no slit, different parts of a galaxy can overlap in the dispersed image. To make reliable emission-line maps from slitless data, the authors use a forward-modeling code called Sleuth, which allows the continuum to vary across the galaxy.
The authors identify clumps using the Hα map together with rest-frame ultraviolet imaging because these tracers are sensitive to star formation on different timescales: Hα highlights gas ionized by the youngest massive stars, while ultraviolet light traces young stellar light over longer periods. As a result a clump can be bright in one and not the other, especially if dust is involved.
To estimate gas-phase metallicity, they use the “strong-line” method, which infers metallicity from ratios of bright emission lines calibrated using models and empirical samples. Their main diagnostic is S23 = ([SIII] + [SII]) / Hα. Because some line ratios also depend on the ionization state (how strongly the gas is being ionized by young stars), they also use the sulfur ratio S32 = [SIII]/[SII] as a check and iterate to a self-consistent solution.
For each clump, the authors measure the metallicity inside the clump and compare it to an annulus just outside the clump (masking neighboring clumps to avoid mixing). When they plot “clump metallicity” versus “local disk metallicity,” most points fall below the 1-to-1 line, meaning the clumps are more metal poor than their surroundings (Figure 1). The mean offset is about 0.1 dex, which corresponds to roughly 20% dilution in the clump gas.
Figure 1: Each point compares a star-forming clump’s gas-phase metallicity to the metallicity of the nearby disk region immediately surrounding it. If clumps and disks had the same metallicity, they would lie on the dashed 1-to-1 line. Instead, most clumps sit below it, showing a typical ∼0.1 dex metallicity deficit, consistent with local chemical dilution. (The solid red line shows a best-fit linear trend to the clump measurement.) [Adapted from Estrada-Carpenter et al. 2025]
If inflow is really the driver, you should expect a link: the more strongly a clump is forming stars relative to its surroundings, the more diluted its metallicity should be. That is exactly what the authors find. The clumps that are most boosted in star formation are also the most metal diluted.
The article also emphasizes that clumps are not chemically uniform blobs. In at least one detailed example, the peaks in Hα (highest star formation) coincide with local minima in metallicity along a cut through the galaxy (Figure 2), suggesting internal star formation rate and metallicity gradients that reinforce the same story, intense star formation goes hand in hand with lower metallicity in the clump regions.
Figure 2: Example galaxy from this study illustrating the clump-scale link between star formation and metallicity. The color image shows the galaxy with a rectangular strip marking the region used for a 1D cut. In the bottom panel, the turquoise line shows the Hα flux (a tracer of recent star formation), while the white line shows the metallicity along the same cut. Peaks in Hα flux line up with local dips in metallicity, showing that the brightest star-forming clumps are also the most chemically diluted compared to nearby regions. [Adapted from Estrada-Carpenter et al. 2025]
A reasonable alternative is that some clumps are actually small companion galaxies projected onto the disk. These could also look metal poor, because low-mass galaxies tend to be low metallicity. The authors look for evidence using face-on systems and find that more massive clumps tend to sit closer to galaxy centers, which is consistent with in-situ clumps that form in the disk and migrate inward, though it does not rule out satellites. They argue that kinematics from JWST/NIRSpec IFU will be needed for a definitive separation.
Gas inflow, star formation, and feedback, together known as the baryon cycle, are key drivers of how galaxies grow. What this article adds is a spatially resolved view that compares each clump to its local environment, showing that regions of elevated star formation also tend to be locally metal poor. That pairing is hard to explain as a simple metallicity gradient or a galaxy-wide averaging effect, and it is exactly what you would expect if at least some clumps are being fueled by relatively metal-poor inflows. In short, these clumps may be snapshots of galaxies refueling in real time.
Original astrobite edited by Ryan White.
About the author, Niloofar Sharei:
I’m an astronomy PhD candidate at UC Riverside studying how galaxies grow through star-forming clumps. I track how these clumps emerge, evolve, and sometimes survive long enough to reshape their galaxies. When I’m not thinking about cosmic blobs, I’m reading, hiking, or listening to Bach.
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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.
Title: Searching Within Galaxies for the Earliest Signs of Quenching With Spatially Resolved Star Formation Histories in UVCANDELS
Authors: Charlotte Olsen et al.
First Author’s Institution: New York City College of Technology
Status: Published in ApJ
Galaxies serve as important laboratories for many subfields of astrophysics. As such, astrophysicists are interested in the full galactic life cycle, from how galaxies are born to the end of their formation. Whereas young galaxies in the distant universe are actively forming stars, many nearby galaxies are much quieter, with little or no ongoing star formation. Astronomers like to describe these galaxies as “red and dead” because their stars are older and therefore appear redder in color. The process by which galaxies shut down their star formation is known as quenching, and it causes galaxies to become quiescent. Understanding the origin of quiescent galaxies is a fundamental question in galaxy evolution. Studying this process is challenging, however, because star formation is intertwined with many other factors that shape galaxies, including their environments and supermassive black holes.
Star formation occurs on scales that are much smaller and over timescales much shorter than the global properties and overall lifetime of a galaxy. By observing star formation on these smaller scales over time, astronomers can gain a clearer picture of how star formation ceases in a galaxy, and they can determine whether this process is driven from the inside out — starting with the supermassive black hole in the galactic center — or from the outside in, influenced by environmental effects. In today’s article, the authors use the Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey with high-resolution ultraviolet coverage (UVCANDELS) to examine eight “golden” galaxies, shown in Figure 1. They then reconstruct the star formation histories within small regions of each galaxy to detect the “earliest signs of quenching.”
Figure 1: Images of the eight galaxies in the “Golden Sample” of galaxies studied in this work (right). These galaxies were chosen because of their clear detection, and they show a range of edge-on to face-on views as well as shapes. The authors divided each galaxy into small, resolved regions in which they measured the star formation (example shown on left). [Adapted from Olsen et al. 2026]
To trace a galaxy’s star formation over cosmic time, today’s authors model its integrated light — which encodes the many episodes of past star formation — using spectral energy distribution (SED) fitting. By comparing a galaxy’s light across many wavelengths to computer models, SED fitting can estimate the ages of its stars and when they formed. This approach allows astronomers to study how a galaxy’s star formation rate evolves as a function of its stellar mass, known as the SFR – Mstellar relation. Note that the article considers the star formation rate and stellar mass in individual regions of each galaxy, so it analyzes these properties as surface densities, ΣSFR and ΣMstellar, instead of the total values.
Using SED fitting, the authors determine the expected star formation rate and stellar mass of the regions from 250 million to 1 billion years before the time of observation. Figure 2 shows the line of best fit for the SFR – Mstellar relation of the regions for each galaxy, before and at the time of observation. The SFR – Mstellar relations are very similar across the sample 1 billion years before the observations; however, by the time of observation, the overall star formation rates have decreased slightly, indicating that the galaxies are beginning to quench. They also exhibit increased variation suggesting that each galaxy is quenching in a different way.
Figure 2: The best-fit SFR – Mstellar relation of the regions for each galaxy, represented by the different colored lines, 1 billion years (1 Gyr) before and at the time of observation (left and right panels, respectively). At 1 billion years before the observation, the galaxies appear to have the same relation, but their variation at the time of observation suggests that the galaxies have begun quenching in different ways. [Olsen et al. 2026]
Figure 3: The specific star formation rate of the regions as a function of their distance from the center for three of the galaxies in the sample. Overall, the star formation rate decreases from 1 billion years before the observation (red) to the time of observation (blue). However, the regions where the star formation decreases most significantly (indicated with the yellow boxes) vary from galaxy to galaxy. [Olsen et al. 2026]
It should be noted that all of the galaxies in this study are still forming stars. However, they are on the verge of having their star formation suppressed, offering valuable insight into how quenching begins and how diverse the process can be. New telescopes are pushing the boundaries of what we can observe. On one hand, JWST can capture galaxies at exceptionally high resolution; on the other, the Vera C. Rubin Observatory and the Nancy Grace Roman Space Telescope will deliver vast datasets containing billions of galaxies. Future investigations leveraging these facilities could reveal more about the physical processes that quench galaxies on small scales, shedding light on the mechanisms that drive galaxy evolution.
Original astrobite edited by Catherine Slaughter.
About the author, Shalini Kurinchi-Vendhan:
After studying astrophysics and literature at Caltech, I moved onto a Fulbright Fellowship in Heidelberg, Germany. I’m passionate about using computer simulations to explore supermassive black holes and galaxy evolution — but I also love poetry and traveling.
The post Observing the End of Star Formation in Galaxies appeared first on AAS Nova.
The full view of the study region, showing the NIRCam and MIRI footprints. [Yoo et al. 2026]
“A JWST NIRCam/MIRI View of the W51A High-Mass Star-Forming Region,” Taehwa Yoo et al 2026 AJ 171 208. doi:10.3847/1538-3881/ae40b7
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One of the most luminous supergiant stars in the Andromeda Galaxy, M31-2014-DS1, has disappeared, potentially leaving behind a black hole shrouded in dusty gas. What do new infrared and X-ray observations tell us about this event?
This image from Gemini North shows the supernova SN 2023ixf along one of the spiral arms of Messier 101. Though less showy than core-collapse supernovae, “failed” supernovae may be another way to form stellar-mass black holes. [International Gemini Observatory/NOIRLab/NSF/AURA; CC BY 4.0]
But a splashy supernova explosion may not be the only way for a massive star to go out. As observations have begun to suggest, some massive stars may — for reasons not yet fully understood — quietly collapse in upon themselves, going out with a whimper rather than a bang. Though less spectacular and far harder to spot, these “failed” supernovae highlight a possible pathway for the formation of stellar-mass black holes.
Just last month, researchers reported their discovery of a potential failed supernova. The supergiant M31-2014-DS1 suddenly brightened in 2014 before fading to obscurity, leading researchers to suspect that the star had experienced a failed supernova and created a black hole. The event shared similarities with another failed supernova candidate, NGC6946-BH1.
Left: A JWST image of M31-2014-DS 1. Right: Spectral energy distributions of the progenitor star/the remnant using data from 2005 to 2012 (empty circles), 2022 to 2023 (filled circles), and 2024 (colored lines). Click to enlarge. [De et al. 2026]
Together, these observations support a model in which the collapsing star ejected its outer layers in a relatively low-energy event (somewhere in the broad ballpark of one hundred-millionth to one ten-thousandth the energy of a typical core-collapse supernova) and formed a black hole. Some of the ejected material fell backward and fed the newborn black hole, while the remainder created a dense blanket that blocked the light from the accreting black hole from view.
Cartoon showing the authors’ model and the model parameters inferred from the observations. Click to enlarge. [De et al. 2026]
Thanks to its location in a neighboring galaxy, M31-2014-DS1 has granted astronomers a front-row seat to a poorly understood pathway for black hole formation. Going forward, we can expect further insights into M31-2014-DS1 and, hopefully, the discovery of many more sources like it.
“Fading into Darkness: A Weak Mass Ejection and Low-Efficiency Fallback Accompanying Black Hole Formation in M31-2014-DS1,” Kishalay De et al 2026 ApJL 999 L25. doi:10.3847/2041-8213/ae468d
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Giant low-surface-brightness galaxies are rare and unusual members of the galactic menagerie. They host the largest galactic disks currently known, have baryonic masses of order 100 billion solar masses, and sport narrow, tightly wound spiral structures. The origins of these vast galaxies — they can be up to 10 times larger than the Milky Way — are unknown, though various theories involving mergers, accretion, and strange dark matter halos exist. Research also suggests that there may be a connection between these galaxies and compact ellipticals, which are small, dense, and contain old stars. In a recent article, a team led by Anna Saburova (Sternberg Astronomical Institute) investigated two giant low-surface-brightness galaxies with compact elliptical companions. In the image above, the colored circles represent the oxygen abundance at each location in AGC 192040 (left) and UGC 1382 (right). The red arrows point to the compact elliptical companions. Using the chemical abundance information to investigate possible formation mechanisms, Saburova and collaborators found that the two galaxies likely formed in different ways. UGC 1382 appears to be the result of multiple mergers, while AGC 192040 may have accreted gas from its halo or a galactic filament before undergoing a merger of its own. To learn more about this study of two rare galaxies, be sure to check out the full research article linked below!
“MUSE Study of Two Giant Low-Surface-Brightness Galaxies with Compact Satellites,” Anna S. Saburova et al 2026 ApJ 998 19. doi:10.3847/1538-4357/ae3139
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Editor’s Note: For the remainder of 2025, we’ll be looking at a few selections that we haven’t yet discussed on AAS Nova from among the most-downloaded articles published in AAS journals this year. The usual posting schedule will resume January 2nd.
A team led by Zoie Telkamp (University of Virginia) used the Stratospheric Observatory for Infrared Astronomy, SOFIA, to study massive protostars and test theories of high-mass star formation. Contrary to the predictions of some star-formation models, the team found no evidence that massive protostars require a certain surface mass density to form. Formation in a cluster environment, however, may limit the formation of the most massive protostars.
Massive stars are rare, short-lived, and luminous. They influence their environments across a vast range of spatial and temporal scales, from advancing the epoch of reionization in the early universe to impacting the formation of individual planetary systems in the present-day universe. The fundamental question of how high-mass stars form is still unsettled. Theories of high-mass star formation range from scaled-up versions of low-mass star formation to scenarios involving collisions between protostars.
SOFIA FORCAST and Herschel Space Observatory images of protostars in the G18.67+0.03 star-forming region. Click to enlarge. [Telkamp et al. 2025]
Zoie Telkamp et al 2025 ApJ 986 15. doi:10.3847/1538-4357/adcd79
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What if there was one process capable of creating every type of detectable stellar-mass black hole system? Recent research suggests there might be, and that it involves a triple-star system.
Stellar-mass black holes, or black holes that are at most a few hundred times the mass of the Sun, pop up in a number of different environments in the Milky Way. Astronomers have known since the 1960s that these black holes are the engines behind accreting low-mass X-ray binaries; more recently, researchers at gravitational wave observatories such as LIGO have found pairs of black holes orbiting each other just prior to merging; and, in just the past few years, scientists using the Gaia spacecraft have found black holes on wide, prowling orbits around still-burning stars.
An illustration of the first black hole discovered with a star on a wide orbit. The black hole moves along the smaller inner ellipse, while its companion star orbits along the wider outer one. [ESA/Gaia/DPAC]
Recent research led by Smadar Naoz (University of California, Los Angeles) offers a potential answer to this question of relatedness — that each of these situations forms through the same underlying process.
A schematic illustration of how triple-star systems can produce all three types of observable stellar-mass black hole systems. Click to enlarge. [Naoz et al. 2025]
What happens next depends on the geometry of the system and the direction of the kick. If the remnant black hole gets shot away from the third star, it might just drift off on its own and leave the star behind. If the kick isn’t too strong, the remnant will remain gravitationally bound to that third star, and the system will eventually look like the star–black hole pairs observed by Gaia. Finally, if the kick sends the remnant toward the third star, some dramatic outcomes become possible: either the black hole starts nibbling on the star and the system becomes a low-mass X-ray binary, or the black hole simply smashes into the star, destroying it completely in a large, flashy explosion paired with a gravitational wave signal.
The authors stress that this mechanism is almost certainly not the only way that these three stellar-mass black hole systems form. However, it is exciting to consider a common thread underlying such seemingly different scenarios, and with upgrades coming to gravitational wave observatories, we can hope for tests of its feasibility in the near future.
“Triples as Links Between Binary Black Hole Mergers, Their Electromagnetic Counterparts, and Galactic Black Holes,” Smadar Naoz et al 2025 ApJL 992 L12. doi:10.3847/2041-8213/ae0a20
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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.
Title: Massive Black Hole Seed Formation in Strong X-Ray Environments at High Redshift
Authors: Kazutaka Kimura, Kohei Inayoshi, and Kazuyuki Omukai
First Author’s Institution: Tohoku University
Status: Published in ApJ
Astronomers have found that nearly every observable galaxy hosts a central supermassive black hole (SMBH) — a black hole more than a million times more massive than the Sun. Using JWST, they have peered back into the early universe to observe some of the earliest galaxies, and these early galaxies also contain SMBHs. In fact, many of these galaxies seem to contain SMBHs that are more massive than we expected them to be this early in the universe.
We believe that most black holes form at the ends of the lives of massive stars, which collapse under their own gravity when they run out of fuel. We expect that this happened to the first stars too, forming “light” (as in “lightweight”) seeds of SMBHs with masses up to about 100 solar masses. Astronomers also think that the right conditions in the early universe could lead to the formation of a “heavy” seed with a mass on the order of 104 solar masses or more; this kind of black hole is called a direct-collapse black hole (DCBH).
In order to form a DCBH, a gas cloud needs to collapse without fragmenting to form star clusters and stars — if stars form, there won’t be enough mass funneled to the center of the cloud to form the DCBH. One important criterion for this to happen is the absence of coolants, like metals and molecular hydrogen (H2), which cause fragmentation. One way to eliminate H2 is with a particular type of ultraviolet light called Lyman-Werner radiation, which can destroy H2 molecules. However, recent results from the Hydrogen Epoch of Reionization Array (HERA) suggest that early galaxies emitted more X-rays than expected, which would increase the amount of H2 and make it less likely for DCBHs to occur. Today’s authors investigate the feasibility of forming DCBHs in these X-ray-bright environments.
Today’s authors model the collapse of gas in dark-matter halos that have a nearby neighboring halo. This neighboring halo emits radiation like ultraviolet light and X-rays that impact the formation of molecules like H2, which affects the gas chemistry. This radiation is typically emitted by hot gas in star-forming regions. The authors also track quantities like the gas density and temperature as the gas collapses. Once the gas collapses enough, a star forms at the center and continues to accrete surrounding material. Once this star evolves and reaches the end of its life, it becomes a black hole.
The authors considered different intensities of X-ray radiation relative to a critical value of Lyman-Werner radiation believed to destroy enough H2 to form a DCBH, which is called J21. They explore values of the X-ray intensity Jx relative to J21, considering ratios of 0, 10-6, 10-5, and 10-4.
Another important consideration was the baryonic streaming velocity. This is the relative bulk velocity between baryonic (i.e., “normal”) matter and dark matter in the early universe. Higher streaming velocities can delay the collapse of gas in dark-matter halos, which affect gas properties like density, temperature, and chemistry. The streaming velocity depends on the redshift, z, which is given by σbsm = 30 km/s (1+z)/(1+z0), where z0 = 1,100. This “standard” relationship has been calibrated with measurements from observations. The authors consider two cases for the streaming velocity: vbsm = 0 and vbsm = 1σbsm, which are denoted in the figures below.
The first main results are shown in Figure 1. The authors find that a large number of intermediate-mass seeds form from H2 cooling, shown in blue, regardless of the X-ray intensity. A smaller number of higher-mass seeds form from H–H2 and H–H cooling, but these cooling processes become suppressed as the X-ray intensity increases. This is because the increased X-ray intensity converts more H to H2. Interestingly, accounting for the streaming velocity all but wipes out black hole formation via H2 cooling except at very high X-ray intensities.
Figure 1: Mass distributions of seed black holes. The top row uses a baryonic streaming velocity of 0 and the bottom row uses the standard streaming velocity. Columns represent increasing X-ray intensities (left to right). Colors represent the dominant cooling mechanisms: H2 (blue), atomic hydrogen H transitioning to H2 (orange), and solely H (green). [Kimura et al. 2025]
Figure 2: Seed black hole mass functions for low and high X-ray intensities (left and right columns, respectively). Rows are the same as in Figure 1. [Kimura et al. 2025]
Original astrobite edited by Sparrow Roch.
About the author, Brandon Pries:
I am a graduate student in physics at Georgia Institute of Technology (Georgia Tech). I do research in computational astrophysics with John Wise, using machine learning to study the formation and evolution of supermassive black holes in the early universe. I’ve also done extensive research with the IceCube Collaboration as an undergraduate at Michigan State University, studying applications of neural networks to event reconstructions and searching for signals of neutrinos from dark matter annihilation.
The post Do X-Rays Help or Hurt Massive Black Hole Formation? appeared first on AAS Nova.
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