noirlab2508 — Science Release

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

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

19 February 2025

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.”

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.

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.

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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.