A fresh look at a classic deep field

An area of deep space with thousands of galaxies in various shapes and sizes on a black background. Most are circles or ovals, with a few spirals. More distant galaxies are smaller, down to being mere dots, while closer galaxies are larger and some appear to be glowing. Red and orange galaxies contain more dust or more stellar activity. Credit: ESA/Webb, NASA & CSA, G. Östlin, P. G. Perez-Gonzalez, J. Melinder, the JADES Collaboration, the MIDIS collaboration, M. Zamani (ESA/Webb)

This image from the NASA/ESA/CSA James Webb Space Telescope revisits one of the most iconic regions of the sky, the Hubble Ultra Deep Field, through the eyes of two of Webb’s instruments. The result is a detailed view that reveals thousands of distant galaxies, some dating back to the earliest periods of cosmic history.

The field shown here, known as the MIRI Deep Imaging Survey (MIDIS) region, was observed with the three shortest-wavelength filters of Webb’s Mid-Infrared Instrument (MIRI) for nearly 100 hours in total. This included Webb's longest observation of an extragalactic field in one filter so far, producing one of the deepest views ever obtained of the Universe. Combined with data from Webb’s Near-Infrared Camera (NIRCam), this image allows astronomers to explore how galaxies formed and evolved over billions of years.

These deep observations have revealed more than 2500 sources in this tiny patch of sky. Among them are hundreds of extremely red galaxies — some of which are likely massive, dust-obscured systems or evolved galaxies with mature stars that formed early in the Universe’s history. Thanks to Webb’s sharp resolution, even at mid-infrared wavelengths, researchers can resolve the structures of many of these galaxies and study how their light is distributed, shedding light on their growth and evolution.

In this image, the colours that have been assigned to different kinds of infrared light highlight the fine distinctions astronomers can make with this deep data. Orange and red represent the longest mid-infrared wavelengths. The galaxies in these colours have extra features — such as high concentrations of dust, copious star formation, or an active galactic nucleus (AGN) at their centre — which emit more of this farther infrared light. Small, greenish-white galaxies are particularly distant, with high redshift. This shifts their light spectrum into the peak mid-infrared wavelengths of the data, which are depicted in white and green. Most of the galaxies in this image lack any such mid-infrared boosting features, leaving them most bright at shorter near-infrared wavelengths, which are depicted with blue and cyan colours.

By returning to this legacy field first made famous by the NASA/ESA Hubble Space Telescope, Webb is continuing and expanding the deep field tradition — revealing new details, uncovering previously hidden galaxies, and offering fresh insights into the formation of the first cosmic structures.

The MIRI observations were taken as part of the Webb programmes #1283 and #6511 (PI: G. Östlin).

Source: ESA/Webb/potm

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Link

• Science paper (G. Östlin et al.)
• Slider Tool
• Pan Video
• Transition video (with Hubble Ultra Deep Field)

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NSF NRAO Achieves First Successful Observations with New NSF VLBA Digital Architecture

Artist interpretation of VNDA First Fringe Result
Credit: M. Weiss U.S. National Science Foundation/NSF National Radio Astronomy Observatory

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The U.S. National Science Foundation National Radio Astronomy Observatory (NSF NRAO) has successfully completed initial observations using its newly upgraded NSF Very Long Baseline Array (NSF VLBA) digital systems, marking a significant milestone in radio astronomy instrumentation. The new NSF VLBA New Digital Architecture (VNDA) produced its first fringes and subsequent images in January 2025, demonstrating the successful implementation of next-generation technology that will enhance the NSF VLBA’s scientific capabilities for years to come.

The NSF VLBA, comprising ten radio antennas spanning from Hawaii to the U.S. Virgin Islands, has received a critical upgrade to replace its aging Roach Digital Back Ends (RDBEs). These digital backends are essential components that convert analog signals from each antenna into digital data for correlation and processing. The obsolete systems faced severe parts shortages, prompting the development of the new VNDA system.

“This upgrade represents a crucial obsolescence mitigation effort that ensures the VLBA will continue to serve both scientific and national interests with enhanced capabilities,” said Walter Brisken of the NSF NRAO, the VLBA Development lead.

The new system has been successfully installed at the Owens Valley and Pie Town NSF VLBA stations, with monitor and control systems functioning as expected. The upgrade includes three primary components:

• New digital radiometer systems (samplers)
• 100 Gbps network switch
• Advanced channelizer system for signal processing

First Light Achievements

The images and data provided in the announcement show the first successful fringes obtained between the Los Alamos station and both Owens Valley and Pie Town stations on January 30, 2025. Fringes—the interference patterns produced when signals from different antennas are combined—confirm that the system is working properly and that precise timing synchronization has been achieved.

Following these initial tests, the team produced high-quality radio images of what appears to be the quasar 3C345, a powerful active galactic nucleus approximately 7.8 billion light-years from Earth. The image clearly shows the bright central core and extended structure of this cosmic radio source.

The VNDA upgrade provides several significant improvements over the previous system:

• Higher sampling rates with more than 8 bits per sample for greater sensitivity
• Improved delay stability through elimination of sampler resets
• Flexible tuning capabilities within frequency bands
• Backward compatibility with existing systems
• Support for user-provided guest equipment such as spectrometers, pulsar backends, and transient detectors

“The VLBA’s incredible resolution—equivalent to standing in New York and reading a newspaper in Los Angeles—depends on precise digital processing of signals from widely separated antennas,” explained Lucas Hunt from the NSF NRAO. “This upgrade ensures we maintain and enhance this capability for the next generation of radio astronomers.”

The successful implementation at two NSF VLBA stations paves the way for upgrading all ten stations in the array. The VNDA project represents a significant investment in the future of very long baseline interferometry in the United States, ensuring this world-class instrument remains at the forefront of radio astronomy research.

The NSF VLBA will continue its scientific mission of studying everything from nearby stars to distant galaxies with unprecedented detail, contributing to our understanding of cosmic phenomena including black holes, stellar evolution, galaxy formation, and the expansion of the universe.

Source: National Radio Astronomy Observatory (NRAO)/News

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About NRAO:

3C345The National Radio Astronomy Observatory is a facility of the U.S. National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

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A New Way to Measure Black Hole Spin

A Hubble Space Telescope image of the relativistic jet emerging from the active supermassive black hole at the heart of the massive elliptical galaxy Messier 87. Credit: NASA, ESA and the Hubble Heritage Team (STScI/AURA); Acknowledgment: P. Cote (Herzberg Institute of Astrophysics) and E. Baltz (Stanford University)

Closeup of Messier 87’s relativistic jet.
Credit: NASA and the Hubble Heritage Team (STScI/AURA)

Upgraded interferometers will give researchers a never-before-seen view of the jets of active supermassive black holes. By modeling what might be seen when these instruments come online, researchers have discovered a new way to measure black hole spin.

Black Holes and Relativistic Jets

Galaxies across the universe harbor supermassive black holes. Determining the properties of these black holes — their masses and spins — is key to understanding the formation and evolution of supermassive black holes and how they shape the evolution of their host galaxies.

Some supermassive black holes produce relativistic particle jets that are thought to be powered by the black hole’s spin. This means that precise observations of black hole jets could provide a potential way to measure the spin of a black hole.

Planned and proposed interferometers will stretch observing baselines to great distances — even into space — to attain the high resolution necessary for this sensitive measurement. Building on the successes of the Event Horizon Telescope, a planet-spanning interferometer that has revealed images of the supermassive black holes at the center of the giant elliptical galaxy Messier 87 and the Milky Way, observatories like the Next-Generation Event Horizon Telescope and the Black Hole Explorer will advance our understanding of supermassive black holes and relativistic jets.

Ray-traced polarized image of a collimated black hole jet. The white bars show the direction of polarization, while the color scale shows the normalized intensity. Several abrupt changes in the polarization direction as a function of radius are visible. Credit: Adapted from Gelles et al. 2025

Tracing Rays from Modeled Jets

To learn what might be gleaned from future images of black holes and black hole jets, Zachary Gelles (Princeton University) and collaborators developed a model of a nearly face-on relativistic black hole jet, much like the jet from Messier 87’s black hole. The team’s model incorporates both general relativistic magnetohydrodynamics, which describes a magnetized fluid subjected to the rules of Einstein’s General Theory of Relativity, and force-free electrodynamics, which focuses on the dynamics of the system’s electromagnetic fields.

With this model in hand, the team used ray tracing — following the paths that photons would take through the modeled jet — to predict how the jet would appear in polarized light. Examining the results for jets with varying degrees of narrowness, or collimation, the team noted that the polarization of the most collimated jet behaved strangely, with the polarization angle changing dramatically with position.

Gelles and coauthors demonstrated that one of these sudden polarization changes happens at the black hole’s light cylinder, or the radius at which the jet becomes relativistic and the magnetic field switches from being mostly poloidal to mostly azimuthal. Because the position of the light cylinder is dependent upon the spin of the black hole, measuring the location of this polarization swing allows for a measurement of the black hole’s spin.

Polarization direction as a function of impact parameter, showing the locations and causes of the abrupt changes in polarization angle.  Credit: Gelles et al. 2025

The Promise of Polarization

This method has several potential advantages over other methods. Unlike the current leading method for measuring black hole spin, X-ray spectroscopy, this method applies to low-luminosity active black holes, which are thought to be common throughout the universe. And while the model includes a number of simplifications, the team asserts that incorporating features of more realistic jets, such as asymmetry, is unlikely to change the outcome.

Gelles’s team also showed that the location of the polarization flip for slowly spinning black holes is 10 times farther out than it is for rapidly spinning black holes. What this means in practice is that determining whether a black hole is slowly or rapidly spinning doesn’t require extraordinarily high resolution, just a general sense of where the flip happens.

Looking forward, Gelles’s team plans to continue their simulations, shoring up their predictions until they can be tested when future interferometers come online.

By Kerry Hensley

Source: American Astronomical Society/AAS-Nova

Citation

“Signatures of Black Hole Spin and Plasma Acceleration in Jet Polarimetry,” Z. Gelles et al 2025 ApJ 981 204. doi:10.3847/1538-4357/adb1aa

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DESI Uncovers 300 New Intermediate-Mass Black Holes Plus 2500 New Active Black Holes in Dwarf Galaxies

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Artist’s illustration of dwarf galaxy with active galactic nucleus

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Dwarf Galaxy AGN Candidates

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Intermediate Black Hole Candidates

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Dwarf AGN Candidates Scatter Plot

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Videos


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Cosmoview Episode 94: DESI Uncovers 300 New Intermediate-Mass Black Holes Plus 2500 New Active Black Holes in Dwarf Galaxies

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Cosmoview Episodio 94: DESI descubre un tesoro de 300 nuevos agujeros negros de masa intermedia y 2.500 agujeros negros activos en galaxias enanasin English only

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Pan across dwarf AGN illustration


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Pan across Dwarf AGN candidates


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Pan across IMBH candidates

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The Dark Energy Spectroscopic Instrument discovers a treasure trove of active black holes in dwarf galaxies and reveals that surprisingly few are of intermediate mass

Within the Dark Energy Spectroscopic Instrument’s early data, scientists have uncovered the largest samples ever of intermediate-mass black holes and dwarf galaxies hosting an active black hole, more than tripling the existing census of both. These large statistical samples will allow for more in-depth studies of the dynamics between dwarf galaxy evolution and black hole growth, and open up vast discovery potential surrounding the evolution of the Universe’s earliest black holes.

Using early data from the Dark Energy Spectroscopic Instrument (DESI), a team of scientists have compiled the largest sample ever of dwarf galaxies that host an actively feeding black hole, as well as the most extensive collection of intermediate-mass black hole candidates to date. This dual achievement not only expands scientists’ understanding of the black hole population in the Universe, but also sets the stage for further explorations regarding the formation of the first black holes to form in the Universe and their role in galaxy evolution.

DESI is a state-of-the-art instrument that can capture light from 5000 galaxies simultaneously. It was constructed, and is operated, with funding from the Department of Energy (DOE) Office of Science. DESI is mounted on the U.S. National Science Foundation (NSF) Nicholas U. Mayall 4-meter Telescope at the NSF Kitt Peak National Observatory, a Program of NSF NOIRLab. The program is now in its fourth of five years surveying the sky and is set to observe roughly 40 million galaxies and quasars by the time the project ends.

The DESI project is an international collaboration of more than 900 researchers from over 70 institutions around the world and is managed by DOE’s Lawrence Berkeley National Laboratory (Berkeley Lab).

With DESI’s early data [1], which include survey validation and 20% of the first year of operations, the team, led by University of Utah postdoctoral researcher Ragadeepika Pucha, was able to obtain an unprecedented dataset that includes the spectra of 410,000 galaxies [2], including roughly 115,000 dwarf galaxies — small, diffuse galaxies containing thousands to several billions of stars and very little gas. This extensive set would allow Pucha and her team to explore the complex interplay between black hole evolution and dwarf galaxy evolution.

While astrophysicists are fairly confident that all massive galaxies, like our Milky Way, host black holes at their centers, the picture becomes unclear as you move toward the low-mass end of the spectrum. Finding black holes is a challenge in itself, but identifying them in dwarf galaxies is even more difficult, owing to their small sizes and the limited ability of our current instruments to resolve the regions close to these objects. An actively feeding black hole, however, is easier to spot.

“When a black hole at the center of a galaxy starts feeding, it unleashes a tremendous amount of energy into its surroundings, transforming into what we call an active galactic nucleus,” says Pucha. “This dramatic activity serves as a beacon, allowing us to identify hidden black holes in these small galaxies.”

From their search the team identified an astonishing 2500 candidate dwarf galaxies hosting an active galactic nucleus (AGN) — the largest sample ever discovered. The significantly higher fraction of dwarf galaxies hosting an AGN (2%) relative to previous studies (about 0.5%) is an exciting result and suggests scientists have been missing a substantial number of low-mass, undiscovered black holes.

In a separate search through the DESI data, the team identified 300 intermediate-mass black hole candidates — the most extensive collection to date. Most black holes are either lightweight (less than 100 times the mass of our Sun) or supermassive (more than one million times the mass of our Sun). The black holes in between the two extremes are poorly understood, but are theorized to be the relics of the very first black holes formed in the early Universe, and the seeds of the supermassive black holes that lie at the center of large galaxies today. Yet they remain elusive, with only around 100–150 intermediate-mass black hole candidates known until now. With the large population discovered by DESI, scientists now have a powerful new dataset to use to study these cosmic enigmas.

“The technological design of DESI was important for this project, particularly its small fiber size, which allowed us to better zoom in on the center of galaxies and identify the subtle signatures of active black holes,” says Stephanie Juneau, associate astronomer at NSF NOIRLab and co-author of the paper. “With other fiber spectrographs with larger fibers, more starlight from the galaxy's outskirts comes in and dilutes the signals we’re searching for. This explains why we managed to find a higher fraction of active black holes in this work relative to previous efforts.”

Typically, black holes found in dwarf galaxies are expected to be within the intermediate-mass regime. But intriguingly, only 70 of the newly discovered intermediate-mass black hole candidates overlap with dwarf AGN candidates. This adds another layer of excitement to the findings and raises questions about black hole formation and evolution within galaxies.

“For example, is there any relationship between the mechanisms of black hole formation and the types of galaxies they inhabit?” Pucha said. “Our wealth of new candidates will help us delve deeper into these mysteries, enriching our understanding of black holes and their pivotal role in galaxy evolution.

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

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Notes

[1] DESI early data is available as files via the DESI collaboration and as searchable databases of catalogs and spectra via the Astro Data Lab and SPARCL at the Community Science and Data Center, a Program of NSF NOIRLab.

[2] DESI's early data contain nearly 3.5 million unique galaxy spectra. The sample used in this work was selected based on redshift (distance) and accurate detection of emission lines.

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More information

This research was presented in a paper titled “Tripling the Census of Dwarf AGN Candidates Using DESI Early Data” to appear in The Astrophysical Journal. DOI: 10.3847/1538-4357/adb1dd. The study can be found ahead of publication here.

The team is composed of Ragadeepika Pucha (University of Utah, University of Arizona), S. Juneau (NSF NOIRLab), Arjun Dey (NSF NOIRLab), M. Siudek (Institute of Space Sciences (ICE-CSIC), Instituto de Astrof´ısica de Canarias), M. Mezcua (ICE-CSIC, Institut d’Estudis Espacials de Catalunya (IEEC)), J. Moustakas (Siena College), S. BenZvi (University of Rochester), K. Hailine (University of Arizona), R. Hviding (Max Planck Institute for Astronomy, University of Arizona), Yao-Yuan Mao (University of Utah), D. M. Alexander (Durham University), R. Alfarsy (University of Portsmouth), C. Circosta (European Space Agency (ESA), University College London), Wei-Jian Guo (National Astronomical Observatories, Chinese Academy of Sciences), V. Manwadkar (Stanford University, SLAC National Accelerator Laboratory), P. Martini (The Ohio State University), B. A. Weaver (NSF NOIRLab), J. Aguilar (Lawrence Berkeley National Laboratory), S. Ahlen (Boston University), D. Bianchi (Università degli Studi di Milano), D. Brooks (University College London), R. Canning (University of Portsmouth), T. Claybaugh (Lawrence Berkeley National Laboratory) K. Dawson (University of Utah), A. de la Macorra (Universidad Nacional Autónoma de México), Biprateep Dey (University of Toronto, University of Pittsburgh), P. Doel (University College London), A. Font-Ribera (University College London, The Barcelona Institute of Science and Technology), J. E. Forero-Romero (Universidad de los Andes), E. Gaztañaga (IEEC, University of Portsmouth, ICE-CSIC), S. Gontcho A Gontcho (Lawrence Berkeley National Laboratory), G. Gutierrez (Fermi National Accelerator Laboratory), K. Honscheid (The Ohio State University), R. Kehoe (Southern Methodist University), S. E. Koposov (University of Edinburgh, University of Cambridge), A. Lambert (Lawrence Berkeley National Laboratory), M. Landriau (Lawrence Berkeley National Laboratory), L. Le Guillou (Sorbonne Université, CNRS/IN2P3), A. Meisner (NSF NOIRLab), R. Miquel (Institució Catalana de Recerca i Estudis Avançats, The Barcelona Institute of Science and Technology), F. Prada (Instituto de Astrofísica de Andalucía (CSIC)), G. Rossi (Sejong University), E. Sanchez (CIEMAT), D. Schlegel (Lawrence Berkeley National Laboratory) M. Schubnell (University of Michigan), H. Seo (Ohio University), D. Sprayberry (NSF NOIRLab), G. Tarlé (University of Michigan), and H. Zou (National Astronomical Observatories, Chinese Academy of Sciences).

This research is supported by the Director, Office of Science, Office of High Energy Physics of the U.S. Department of Energy, and by the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility; additional support for DESI is provided by the U.S. National Science Foundation, Division of Astronomical Sciences; the Science and Technology Facilities Council of the United Kingdom; the Gordon and Betty Moore Foundation; the Heising-Simons Foundation; the French Alternative Energies and Atomic Energy Commission (CEA); the National Council of Humanities, Science and Technology of Mexico (CONAHCYT); the Ministry of Science, Innovation and Universities of Spain (MICIU/AEI/10.13039/501100011033), and by the DESI Member Institutions. The authors are honored to be permitted to conduct scientific research on I’oligam Du’ag (Kitt Peak), a mountain with particular significance to the Tohono O’odham Nation.

Current DESI Member Institutions include: Aix-Marseille University; Argonne National Laboratory; Barcelona-Madrid Regional Participation Group; Brookhaven National Laboratory; Boston University; Brazil Regional Participation Group; Carnegie Mellon University; CEA-IRFU, Saclay; China Participation Group; Cornell University; Durham University; École Polytechnique Fédérale de Lausanne; Eidgenössische Technische Hochschule, Zürich; Fermi National Accelerator Laboratory; Granada-Madrid-Tenerife Regional Participation Group; Harvard University; Kansas State University; Korea Astronomy and Space Science Institute; Korea Institute for Advanced Study; Lawrence Berkeley National Laboratory; Laboratoire de Physique Nucléaire et de Hautes Energies; Ludwig Maximilians University; Max Planck Institute; Mexico Regional Participation Group; National Taiwan University; New York University; NSF’s National Optical-Infrared Astronomy Research Laboratory; Ohio University; Perimeter Institute; Shanghai Jiao Tong University; Siena College; SLAC National Accelerator Laboratory; Southern Methodist University; Swinburne University; The Ohio State University; Universidad de los Andes; University of Arizona; University of Barcelona; University of California, Berkeley; University of California, Irvine; University of California, Santa Cruz; University College London; University of Florida; University of Michigan at Ann Arbor; University of Pennsylvania; University of Pittsburgh; University of Portsmouth; University of Queensland; University of Rochester; University of Toronto; University of Utah; University of Waterloo; University of Wyoming; University of Zurich; UK Regional Participation Group; Yale University. For more information, visit desi.lbl.gov.

Lawrence Berkeley National Laboratory addresses the world’s most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab’s scientific expertise has been recognized with 13 Nobel prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy’s Office of Science. For more, visit http://www.lbl.gov.

DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

NSF NOIRLab, the U.S. National Science Foundation center for ground-based optical-infrared astronomy, operates the International Gemini Observatory (a facility of NSF, NRC–Canada, ANID–Chile, MCTIC–Brazil, MINCyT–Argentina, and KASI–Republic of Korea), NSF Kitt Peak National Observatory (KPNO), NSF Cerro Tololo Inter-American Observatory (CTIO), the Community Science and Data Center (CSDC), and NSF–DOE Vera C. Rubin Observatory (in cooperation with DOE’s SLAC National Accelerator Laboratory). It is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with NSF and is headquartered in Tucson, Arizona.

The scientific community is honored to have the opportunity to conduct astronomical research on I’oligam Du’ag (Kitt Peak) in Arizona, on Maunakea in Hawai‘i, and on Cerro Tololo and Cerro Pachón in Chile. We recognize and acknowledge the very significant cultural role and reverence of I’oligam Du’ag (Kitt Peak) to the Tohono O’odham Nation, and Maunakea to the Kanaka Maoli (Native Hawaiians) community.

The National Science Foundation (NSF) is an independent federal agency created by Congress in 1950 to promote the progress of science. NSF supports basic research and people to create knowledge that transforms the future. Please refer to www.nsf.gov.

Established in 2007 by Mark Heising and Elizabeth Simons, the Heising-Simons Foundation (www.heisingsimons.org) is dedicated to advancing sustainable solutions in the environment, supporting groundbreaking research in science, and enhancing the education of children.

The Gordon and Betty Moore Foundation, established in 2000, seeks to advance environmental conservation, patient care and scientific research. The Foundation’s Science Program aims to make a significant impact on the development of provocative, transformative scientific research, and increase knowledge in emerging fields. For more information, visit www.moore.org.

The Science and Technology Facilities Council (STFC) of the United Kingdom coordinates research on some of the most significant challenges facing society, such as future energy needs, monitoring and understanding climate change, and global security. It offers grants and support in particle physics, astronomy and nuclear physics, visit www.stfc.ac.uk.

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Links

• Read the paper: Tripling the Census of Dwarf AGN Candidates Using DESI Early Data
• Press release by University of Utah
• Press release by University of Portsmouth
• Press release by ICE-CSIC
• Interview with Ragadeepika Pucha on DESI Blog
• Visit the Dark Energy Spectroscopic Instrument webpage
• Images of DESI
• Videos of DESI
• Images of Nicholas U. Mayall 4-meter telescope
• Videos of Nicholas U. Mayall 4-meter telescope
• Check out other NOIRLab Science Releases

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Contacts

Ragadeepika Pucha
University of Utah
Postdoctoral Researcher
Email: dr.raga.pucha@gmail.com

Stephanie Juneau
Associate Astronomer
NSF NOIRLab
Email: stephanie.juneau@noirlab.edu

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

NSF VLA Contributes Crucial Puzzle Piece to ‘Peculiar’ High Energy Transient

Illustration of a tidal disruption event
Credit: ESA/C. Carreau
Hi-Res File

An artist's concept of the Einstein probe
Credit: NSF/AUI/NSF NRAO/J.Hellerman
Hi-Res File

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Non-detection at radio wavelengths may prove to be the critical clue toward categorizing EP240408a as an entirely new phenomenon

High-energy transient signals are most often determined to be gamma-ray burst events, but the recently-launched Einstein Probe has expanded astronomers’ ability to quickly respond to similar signals occurring at X-ray wavelengths. Now, a multi-wavelength study of EP240408a concludes that while many of the signal’s characteristics might lead to the conclusion that it is a gamma-ray burst, the non-detection at radio wavelengths precludes that possibility. Instead, the international team of astronomers suggest that EP240408a is either a rare jetted tidal disruption event or, perhaps, an entirely new type of astronomical phenomenon. This was discovered in only the first two months of the commissioning phase.

Tidal disruption events (TDEs) occur when a star is shredded by a nearby black hole; these events are themselves rare, with fewer than 100 discovered so far. In even more rare cases, the black hole’s powerful tidal forces propel some of the shredded stellar material outward in high-velocity jets, which then interact with nearby clouds of dust and gas and shine brightly in X-ray and radio. Thus far, only four TDEs are known to have relativistic-velocity jets associated with them

An international team of astronomers led by Brendan O’Connor, an astronomer at Carnegie Mellon University, analyzed the signal from EP240408a across the span of wavelengths from radio to X-ray and concluded that this X-ray transient is—thus far—unique. “It ticks the boxes for a bunch of different kinds of phenomena, but it doesn’t tick all of the boxes for anything,” O’Connor summarizes. “And I think the radio non-detection is a massive box that we don’t know how to not tick.”

The team’s expansive follow-up campaign further characterized the X-ray emissions from EP240408a and identified a potential host galaxy in optical wavelengths. Crucially, however, O’Connor notes the non-detection in radio wavelengths as potentially the deciding factor in fully categorizing the source. Observations from the U.S. National Science Foundation Very Large Array (NSF VLA), operated by the U.S. National Science Foundation National Radio Astronomy Observatory (NSF NRAO), at 11 days, 158 days, and 258 days after EP240408a’s initial discovery indicated no radio emission from the source.

“I think where radio really fits in is that when we see something this bright, for this long, in X-rays, it usually has an extremely luminous radio counterpart. And here we see nothing, which is extremely peculiar,” O’Connor says.

After methodically eliminating a number of potential explanations including active galactic nuclei, fast blue optical transients, fast X-ray transients, and other variations of previously-characterized phenomena, O’Connor and his co-authors conclude that EP240408a is extragalactic in origin and is most likely a relativistically-jetted Tidal Disruption Event.

“Because of this new wide field view of the X-ray universe, there’s a diverse range of phenomena we can see that weren’t possible before. And it looks like this transient, EP 240408a, is new. It’s something that we don’t think we’ve seen before,” O’Connor says. “It’s falling in a range of energy, of wavelengths, that it can be detected at, and the time scales are so short, that it’s probably something that we’ve just missed before now.”

O’Connor emphasizes that the current lack of radio emissions is pivotal, but that follow-up observations in radio wavelengths will hopefully yield future detections as the material within the jets slows down to energies corresponding to radio—a process expected to occur on timescales of roughly 1000 days. Thus, follow-up radio observations with the NRAO VLA will be imperative.

Thus, EP240408a appears to be giving astronomers an in-between glimpse of a high-energy transient’s signal after its initial X-ray outburst but before its relativistic-speed jet flares in radio. “It seems to me that this is the most likely explanation for why we aren’t seeing radio emission. Hopefully, eventually, we will see a jet at radio wavelengths, either with the current setup of the VLA or the Next Generation VLA, and we can monitor it for years to come in order to learn even more about this explosion,” O’Connor muses;

“These results highlight the importance of multiwavelength observations in fully understanding the astronomical object,” says Joe Pesce, NSF Program Director for the NRAO. “The complete picture of what’s really happening requires a holistic study.”

An international team of astronomers were involved in the study, including Dheeraj Pasham at MIT, Igor Andreoni at the University of North Carolina Chapel Hill, Jeremy Hare at the Catholic University of America, Paz Beniamini at the Open University of Israel, and Eleonora Troja at the University of Rome Tor Vergata, among others. You can read the full scientific paper here.

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

Source: National Radio Astronomy Observatory (NRAO)/News

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Zooming in on a supermassive black hole in action

An image of the spiral galaxy NGC 1068 (Messier 77) obtained by the European Southern Observatory’s (ESO) Very Large Telescope (VLT). The galaxy has a distance of 14.4 Mpc (47 million light-years) and is one of the nearest galaxies with an active galactic nucleus. © ESO

A new type of observation reveals what makes the cores of active galaxies glow

Using the Large Binocular Telescope Interferometer, a team of astronomers led by scientists from the Max Planck Institute for Astronomy (MPIA) and the University of Arizona (UofA) has disentangled the sources of infrared radiation near the supermassive black hole at the centre of the galaxy NGC 1068. They discovered that the surrounding dusty wind is heated by the hot central accretion disk and shocks generated by a collimated gas jet. These findings and additional features support the unified model of active galactic nuclei, which explains their varying appearances.

Active galactic nuclei (AGN) are supermassive black holes at the centre of certain galaxies. When these black holes attract matter, a quickly rotating disk of hot gas forms, releasing enormous amounts of energy before plunging into the black hole. Such AGN belong to the most energetic phenomena observed in space. As a result, they also influence processes occurring in their host galaxies. The details are a field of ongoing research.

A team around former MPIA student Jacob Isbell, now a postdoc at the Steward Observatory of the University of Arizona, aimed the Large Binocular Telescope (LBT) at the galaxy NGC 1068, also known as Messier 77, to study the minute details in its centre at thermal infrared wavelengths. This galaxy is one of the nearest with an AGN. The observations had the proper spatial resolution to focus on the components emitting this kind of radiation. The results are now published in Nature Astronomy.

An optical image of the spiral galaxy NGC 1068 (Messier 77) overlaid with an insert with the image obtained by the Large Binocular Telescope Interferometer (LBTI) at thermal infrared wavelengths (8.7 micrometres). The false-colour image depicts the brightness variation of mostly warm dust surrounding the supermassive black hole in the centre of that galaxy. By comparing the image with previous observations at various wavelengths, the researchers identified the hot and bright disk of gas and dust and the collimated gas jet as their heat sources. The components identified in the image confirm the unified model of active galactic nuclei. © ESO / J. Isbell (UofA, MPIA) / MPIA

Disentangling the AGN components

The bright, hot disk surrounding the supermassive black hole emits an enormous amount of light that drives the dust apart as if the individual grains were tiny sails – a phenomenon known as radiation pressure. The images revealed the glowing dust, a warm, outflowing wind caused by that mechanism, which was heated by the hot central disk.

Simultaneously, farther out, much material is way brighter than it should have been if it was illuminated only by the bright accretion disk. By comparing the new images to past observations at various wavelengths, the researchers tied this finding to a collimated jet of hot gas emanating from the disk centre. While blasting through the galaxy, it hits and heats clouds of molecular gas and dust, leading to the unexpected bright infrared signal. Such jets are particularly bright at radio wavelengths when interacting with gas and particles in the environment around the supermassive black holes.

Altogether, the result confirms the so-called unified model of AGN. It promotes a configuration of a supermassive black hole in the centre of a galaxy, which attracts and collects gas and dust from the surrounding host galaxy, accumulating in an inner bright and hot disk. In addition, an outer, larger structure of cooler, outflowing material obstructs the view. Finally, a powerful gas jet is ejected from the centre. Different components are exposed to the observer, depending on the viewing angle. Although the observed features vary significantly between objects, the unified model proposes that those variations derive from intrinsically similar configurations of structures around the supermassive black hole, powering the AGN phenomenon.

View from the dome of the Large Binocular Telescope (LBT) through the open dome doors. In the foreground are the two large primary mirrors with the support structure for the secondary mirrors. © Marc-André Besel & Wiphu Rujopakarn

LBT – A precursor of future segmented-mirror telescopes

The LBT is located on Mount Graham, northeast of Tucson, USA, and operates its two 8.4-metre mirrors independently of each other, essentially functioning like two separate telescopes mounted side by side and aligned in parallel. MPIA is a member of the LBT Corporation via the LBT-Beteiligungsgesellschaft (holding company), which supplies 25% of all operations funding.

Combining the light from both mirrors, the LBT becomes an imaging interferometer (LBTI), allowing for approximately three times higher resolution observations than would be possible with each mirror on its own. To stabilize this high-resolution imaging machine, LBTI regularly deploys the OVMS+ vibration control system developed under MPIA leadership by MPIA’s Jörg-Uwe Pott to enable these challenging observations of distant galaxies. This imaging technique has been successfully employed to study volcanoes on the surface of Jupiter’s moon Io. The Jupiter results encouraged the researchers to use the interferometer to look now at an AGN.

“The AGN within the galaxy NGC 1068 is especially bright, so it was the perfect opportunity to test this method,” Isbell said. “These are the highest resolution direct images of an AGN taken so far.” In this context, direct images mean, they contain all faint and diffuse radiation from the structures observed. In contrast, images from other interferometers, such as the Very Large Telescope Interferometer (VLTI), are reconstructed from computations interpolating the missing imaging information.

Combining both mirrors produces images directly on the detector, very much like telescopes with segmented mirrors do, such as the James Webb Space Telescope, as well as the future 25-metre Giant Magellan Telescope (GMT) and the upcoming 39-metre Extremely Large Telescope (ELT), both being built in Chile. This way, Isbell and his collaborators produced the first ELT-like images of an AGN. As a result, the LBTI observations resolved individual features of up to 20 light-years at a distance of 47 million light-years. Previously, the various processes were blended due to low resolution, but now it is possible to view their individual impact.

A test for future observations

The study shows that the environments of AGN can be complex. The new findings help us understand the intricate ways in which AGN interact with their host galaxies. By probing distant galaxies in the early universe, when the galaxies were still young, we cannot achieve the same level of detail. Therefore, these results are like a local analogue.

“This type of imaging can be used on any astronomical object,” Isbell said. “We’ve already started looking at disks around stars and very large, evolved stars, which have dusty envelopes around them.”

Additional information

The MPIA team involved in this study comprised Jacob W. Isbell (now Steward Observatory, The University of Arizona, Tucson, USA) and Jörg-Uwe Pott.

Other researchers included Steve Ertel (Steward Observatory and Large Binocular Telescope Observatory, The University of Arizona, Tucson, USA), Gerd Weigelt (Max Planck Institute for Radio Astronomy, Bonn, Germany), and Marko Stalevski (Astronomical Observatory, Belgrade, Serbia and Sterrenkundig Observatorium, Universiteit Gent, Belgium).

This press release is based on the one published by the University of Arizona.

Source: Max Planck Institute for Astronomy/Press Releases

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Contacts:

Dr. Markus Nielbock
Press and outreach officer
+49 6221 528-134
pr@mpia.de
MPIA press department
Max Planck Institute for Astronomy, Heidelberg, Germany

Dr. Jacob W. Isbell
jwisbell@arizona.edu
Jacob Isbell / UofA
Steward Observatory, The University of Arizona, Tucson, AZ, USA

Dr. Jörg-Uwe Pott
+49 6221 528-202
jpott@mpia.de
Jörg-Uwe Pott / MPIA
Max Planck Institute for Astronomy, Heidelberg, Germany

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Original publication

Jacob W. Isbell, S. Ertel, J.-U. Pott et al.
Direct imaging of active galactic nucleus outflows and their origin with the 23 m Large Binocular Telescope
Nature Astronomy (2025)

Source | DOI

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Video

The Unified Model of active galactic nuclei
Credit: ESO/L. Calçada and M. Kornmesser

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Links

Nature Astronomy embargo policy
Ring of cosmic dust hides a supermassive black hole in Active Galactic Nucleus

February 16, 2022
Image of warm dust emission from the heart of an active galactic nucleus shows a ring-like structure that obscures the black hole

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Newfound Galaxy Class May Indicate Early Black Hole Growth, Webb Finds

Little Red Dots (NIRCam Image)
Credits/Image: NASA, ESA, CSA, STScI, Dale Kocevski (Colby College)

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In December 2022, less than six months after commencing science operations, NASA’s James Webb Space Telescope revealed something never seen before: numerous red objects that appear small on the sky, which scientists soon called “little red dots” (LRDs). Though these dots are quite abundant, researchers are perplexed by their nature, the reason for their unique colors, and what they convey about the early universe.

A team of astronomers recently compiled one of the largest samples of LRDs to date, nearly all of which existed during the first 1.5 billion years after the big bang. They found that a large fraction of the LRDs in their sample showed signs of containing growing supermassive black holes.

“We’re confounded by this new population of objects that Webb has found. We don’t see analogs of them at lower redshifts, which is why we haven’t seen them prior to Webb,” said Dale Kocevski of Colby College in Waterville, Maine, and lead author of the study. “There's a substantial amount of work being done to try to determine the nature of these little red dots and whether their light is dominated by accreting black holes.”

A Potential Peek Into Early Black Hole Growth

A significant contributing factor to the team’s large sample size of LRDs was their use of publicly available Webb data. To start, the team searched for these red sources in the Cosmic Evolution Early Release Science (CEERS) survey before widening their scope to other extragalactic legacy fields, including the JWST Advanced Deep Extragalactic Survey (JADES) and the Next Generation Deep Extragalactic Exploratory Public (NGDEEP) survey.

The methodology used to identify these objects also differed from previous studies, resulting in the census spanning a wide redshift range. The distribution they discovered is intriguing: LRDs emerge in large numbers around 600 million years after the big bang and undergo a rapid decline in quantity around 1.5 billion years after the big bang.

The team looked toward the Red Unknowns: Bright Infrared Extragalactic Survey (RUBIES) for spectroscopic data on some of the LRDs in their sample. They found that about 70 percent of the targets showed evidence for gas rapidly orbiting 2 million miles per hour (1,000 kilometers per second) – a sign of an accretion disk around a supermassive black hole. This suggests that many LRDs are accreting black holes, also known as active galactic nuclei (AGN).

“The most exciting thing for me is the redshift distributions. These really red, high-redshift sources basically stop existing at a certain point after the big bang,” said Steven Finkelstein, a co-author of the study at the University of Texas at Austin. “If they are growing black holes, and we think at least 70 percent of them are, this hints at an era of obscured black hole growth in the early universe.”

Contrary to Headlines, Cosmology Isn’t Broken

When LRDs were first discovered, some suggested that cosmology was “broken.” If all of the light coming from these objects was from stars, it implied that some galaxies had grown so big, so fast, that theories could not account for them.

The team’s research supports the argument that much of the light coming from these objects is from accreting black holes and not from stars. Fewer stars means smaller, more lightweight galaxies that can be understood by existing theories.

“This is how you solve the universe-breaking problem,” said Anthony Taylor, a co-author of the study at the University of Texas at Austin.

Curiouser and Curiouser

There is still a lot up for debate as LRDs seem to evoke even more questions. For example, it is still an open question as to why LRDs do not appear at lower redshifts. One possible answer is inside-out growth: As star formation within a galaxy expands outward from the nucleus, less gas is being deposited by supernovas near the accreting black hole, and it becomes less obscured. In this case, the black hole sheds its gas cocoon, becomes bluer and less red, and loses its LRD status.

Additionally, LRDs are not bright in X-ray light, which contrasts with most black holes at lower redshifts. However, astronomers know that at certain gas densities, X-ray photons can become trapped, reducing the amount of X-ray emission. Therefore, this quality of LRDs could support the theory that these are heavily obscured black holes.

The team is taking multiple approaches to understand the nature of LRDs, including examining the mid-infrared properties of their sample, and looking broadly for accreting black holes to see how many fit LRD criteria. Obtaining deeper spectroscopy and select follow-up observations will also be beneficial for solving this currently “open case” about LRDs.

“There’s always two or more potential ways to explain the confounding properties of little red dots,” said Kocevski. “It’s a continuous exchange between models and observations, finding a balance between what aligns well between the two and what conflicts.”

These results were presented in a press conference at the 245th meeting of the American Astronomical Society in National Harbor, Maryland, and have been accepted for publication in The Astrophysical Journal.

The James Webb Space Telescope is the world’s premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency).

Source: NASA's James Webb Space Telescope/News

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About This Release

Credits:

Media Contact:

Abigail Major
Space Telescope Science Institute, Baltimore, Maryland

Christine Pulliam
Space Telescope Science Institute, Baltimore, Maryland

Science: Dale Kocevski (Colby College)

Permissions: Content Use Policy

Contact Us: Direct inquiries to the News Team.

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Seeing an Active Galactic Nucleus with 20/20 X-Ray Vision with XRISM

This multiwavelength image shows X-rays (blue), optical light (yellow), and radio waves (red) from the galaxy NGC 4151, which hosts an active galactic nucleus. Credit: X-ray: NASA/CXC/CfA/J.Wang et al.; Optical: Isaac Newton Group of Telescopes, La Palma/Jacobus Kapteyn Telescope, Radio: NSF/NRAO/VLA

Title: XRISM Spectroscopy of the Fe Kα Emission Line in the Seyfert Active Galactic Nucleus NGC 4151 Reveals the Disk, Broad-line Region, and Torus
Authors: XRISM Collaboration
Status: Published in ApJL

Today we’re going to be taking a high-resolution look at X-rays from close to a supermassive black hole! But before we get into the astrophysics of today’s article, we first need to discuss the instruments that were built to do this science. More than 50 years ago now, charge-coupled devices (CCDs) began revolutionizing astronomy, and they continue to be one of the most commonly used detectors on telescopes. CCDs rely on the photoelectric effect, through which an incoming photon can liberate electrons in some material (semiconductors in the case of CCDs). These electrons are trapped by strong potential wells and electric charge can be applied to move the charge along and read this signal (check out this Astrobite for more details). CCDs are particularly powerful in the X-ray band, where the number of electrons trapped in each pixel scales roughly with the photon energy. This means that you get energy information (i.e., a spectrum) for free with CCDs! However, CCDs have limited spectral resolution, meaning they can’t determine this energy very precisely and therefore cannot resolve and unlock the power of narrow emission and absorption lines.

Figure 1: Schematic showing how a microcalorimeter works. An X-ray photon with energy E will produce a spike in the temperature of the absorber of E/C, where C is the heat capacity of the absorber. The thermometer is extremely sensitive to small changes in temperature, which means that we can get very accurate energies for each of the incoming X-ray photons. Therefore, a microcalorimeter can produce an X-ray spectrum with the best energy resolution of any current instrumentation. Credit: NASA

X-Ray Microcalorimetry and 20/20 Vision

There are other ways to get better spectral resolution in the X-ray, including using gratings that will disperse your spectrum, as is commonly done with optical spectroscopy. However, even these techniques can’t reach the high spectral resolution needed; instead, new technology called a microcalorimeter has been engineered to solve this long-standing issue. As the name suggests, this instrument detects incoming photons by measuring tiny (micro) changes to the temperature (calorimetry) of the detector. Figure 1 shows the basic set-up of a microcalorimeter and how the energy of the photon is encoded in the strength of the resulting temperature fluctuation. In order to detect tiny changes to the temperature, microcalorimeters need to be extremely cold, 50 millikelvin to be precise! This is a huge engineering feat, but one that has recently been achieved by the X-ray Imaging and Spectroscopy Mission (XRISM)! XRISM is a JAXA/NASA collaborative mission, and it has two instruments on board: a CCD camera called Xtend and a microcalorimeter called Resolve. It was launched in September 2023, and its first science results are just starting to roll in!

Now, XRISM isn’t actually the first X-ray microcalorimeter to fly, but it’s the first to live through its commissioning phase! Although the X-ray microcalorimeter has been in the works since the 1990s, previous X-ray microcalorimeters have been cut from missions, lost to launch failures, and left unable to operate due to loss of coolant for the detector. In 2016, JAXA successfully launched and operated the first X-ray microcalorimeter on the Hitomi Satellite. However, unfortunately, shortly after taking a beautiful spectrum of the Perseus Cluster, one of the best-studied galaxy clusters in the local universe, communication was lost with the satellite and never recovered. XRISM’s Resolve instrument has been the most successful X-ray microcalorimeter so far, and it has allowed us to start looking at the universe with 20/20 X-ray vision!

Figure 2: XRISM Resolve spectra of NGC 4151. The left panels show the spectrum in the 5.8-7.2 keV range from two separate observations, with the data in black and the best fit total model in red. The right panels show a zoom in on the iron Kα 6.4 keV line with the three different components for the line also shown. The magenta model corresponds to the widest line, arising potentially from a warped disk, the dark blue model corresponds to the intermediate width line coming from the inner edge of the broad line region (BLR), and the cyan model corresponds to the most narrow line that arises from the inner edge of the dusty torus. Credit: XRISM Collaboration et al. 2024 universe with 20/20 X-ray vision!

Supermassive Science with XRISM

Today we’re going to put on our high-resolution X-ray spectroscopy glasses to look at one of the first XRISM targets: NGC 4151, one of the most well-known active galactic nuclei in the local universe. An active galactic nucleus consists of a supermassive black hole that is gobbling down gas from its surroundings through a process known as accretion. While we’ve known about active galactic nuclei for more than 50 years now, we still don’t really understand how they are fueled and what the structure is around them. XRISM can unlock this information indirectly by resolving some of the key X-ray emission and absorption lines. In particular, the most prominent emission line in the X-ray spectrum of an active galactic nucleus is a neutral iron Kα line at 6.4 kiloelectronvolts (keV), which arises from material around the supermassive black hole being illuminated by the light from the accretion process. This line holds the keys to probing the structure of the surrounding gas, as its dynamics can tell us about the structure of the accretion disk and trace gas in the torus that is thought to connect the local host galaxy to the accretion flow.

Figure 2 shows the XRISM Resolve spectrum of NGC 4151 from two separate observations. The spectrum shows a prominent 6.4 keV line that is resolved, meaning that the measured width of the line is greater than the instrument’s resolution limit. Additionally, the line cannot be fit with a single emission line and instead requires multiple lines, signaling multiple physical scales contributing to this emission line. The right panels of this figure highlight that there are three distinct components to this emission line with broad (magenta), intermediate (dark blue), and narrow (cyan) widths. Since gas that is closer to the black hole will be moving faster than more distant gas, the authors can use these line widths to estimate where this gas is located. They find that these three lines range from about 100 gravitational radii (about 100 times the size of the black hole) to about 10,000 gravitational radii. Determining the multi-scale nature of this line has been extraordinarily difficult to detect with other instruments due to their limited energy resolution!

Together these three components to the iron Kα line provide a compelling picture for the nuclear structure, which is shown in Figure 3. There are some additional pieces of evidence from the data that support this model as well. For example, the broadest line (magenta) shows variability on timescales of less than a day. This timescale corresponds roughly to the distance light could travel before reaching the magenta part of this figure, supporting the idea that there is a broad component associated with the disk. In addition to the location of the emitting gas, the dynamics and density can be constrained using the energy and shape of the line, respectively. In this source, the line is at the rest-frame energy and the shape is relatively symmetric, which together suggest that the emission comes from relatively optically thin gas that has not been accelerated to high velocities. Together, these diagnostics give one of the most in-depth pictures of supermassive black hole environments to date and will be crucial for testing our models of black hole feeding!

Figure 3: Schematic highlighting where each of the iron Kα emission lines arise from. The magenta component corresponds to the broadest line, potentially from a warp in the disk. The dark blue component corresponds to the intermediate-width line and arises from the inner edge of the broad line region (BLR). The cyan component corresponds to the narrowest line and arises from the inner edge of the active galactic nucleus torus. Credit: XRISM Collaboration et al. 2024

What’s Next?

These XRISM observations are rich with information, and today’s article focused only on the 6.4 keV emission line. The authors are planning a series of further articles, including on the active galactic nucleus winds traced by the absorption lines (i.e., the major dips seen at ~6.7 and ~7 keV in the left panels of Figure 2), comparisons of the emission lines with optical emission lines, and looking for faint evidence of broader emission from even closer to the supermassive black hole. The next obvious steps are also to observe more active galactic nuclei to test whether this multi-zone emission is a common occurrence in active galactic nuclei. One thing’s for sure, this 20/20 vision is sure to reveal new secrets about the lives and environments of supermassive black holes!

Original astrobite edited by Roel Lefever

Source: American Astronomical Society/AAS-Nova

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

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About the author, Megan Masterson:

I’m a 4th-year PhD student at MIT studying transient accretion events around supermassive black holes, including tidal disruption events and changing-look active galactic nuclei. I primarily use multi-wavelength observations to study from the inner accretion flow to the obscuring material in these transients. In my free time, you’ll find me hiking, reading, and watching women’s soccer.

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Hubble revisits a grand spiral

NGC 5643

A close-up of a spiral galaxy, seen face-on. Its center is a bright white point, surrounded by a large yellowish oval with thin lines of dust swirling in it. From the sides of the oval emerge two bright spiral arms which wind through the round disc of the galaxy, filled with shining pink spots where stars are forming and more dark reddish dust. Many stars can be seen in the foreground, over and around the galaxy. Credit: ESA/Hubble & NASA, A. Riess, D. Thilker, D. De Martin (ESA/Hubble), M. Zamani (ESA/Hubble)

Today’s NASA/ESA Hubble Space Telescope Picture of the Week features the glorious spiral galaxy NGC 5643, which is located roughly 40 million light-years away in the constellation Lupus. NGC 5643 is what’s known as a grand design spiral, referring to how the galaxy’s two large, winding spiral arms are clear to see. The spiral arms are defined by bright blue stars, lacy reddish-brown dust clouds and pink star-forming regions.

As fascinating as the galaxy appears at visible wavelengths, some of NGC 5643’s most interesting features are invisible to the human eye. Ultraviolet and X-ray images and spectra of NGC 5643 show that the galaxy hosts an active galactic nucleus: an especially bright galactic core powered by a feasting supermassive black hole. When a supermassive black hole ensnares gas from its surroundings, the gas collects in a disc that heats up to hundreds of thousands of degrees. The superheated gas shines brightly across the electromagnetic spectrum, but especially at X-ray wavelengths.

NGC 5643’s active galactic nucleus isn’t the brightest source of X-rays in the galaxy, though. Researchers using ESA’s XMM-Newton discovered an even brighter X-ray-emitting object, called NGC 5643 X-1, on the galaxy’s outskirts. What could be a more powerful source of X-rays than a supermassive black hole? Surprisingly, the answer appears to be a much smaller black hole! While the exact identity of NGC 5643 X-1 is not yet known, evidence points to a black hole that is about 30 times more massive than the Sun. Locked in an orbital dance with a companion star, the black hole ensnares gas from its stellar companion, creating a superheated disc that outshines the galactic centre.

NGC 5643 was also the subject of a previous Picture of the Week. The new image incorporates additional wavelengths of light, including the red color that is characteristic of gas heated by massive young stars.

Source: ESA/Hubble/potw

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