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A team of astronomers using the JWST has discovered an unusually red, gravitationally lensed supermassive black hole from the early universe, revealing it to be significantly larger relative to its host galaxy than previously observed examples. This finding challenges our understanding of the relationship between black holes and galaxies in the early cosmos. Credit: SciTechDaily.com
JWST images reveal a supermassive black hole in the early universe, notable for its enormous size compared to its host galaxy and obscured by thick dust.
By analyzing images from the James Webb Space Telescope (JWST), a group of astronomers led by Dr. Lukas Furtak and Prof. Adi Zitrin of Ben-Gurion University of the Negev has detected an extremely red, gravitationally lensed supermassive black hole, in the early Universe. . Its colors suggest that the black hole lies behind a thick veil of dust that obscures much of its light. The team managed to measure the mass of the black hole and found that it was significantly more massive, compared to its host galaxy, than had been seen in more local examples. The discovery was published in Nature two weeks ago.
JWST: Revealing the mysteries of the early universe
JWST, launched two years ago, has revolutionized our view of early galaxy formation. It has led to the detection of very early galaxies with higher abundances and brightnesses than previously predicted, and has revealed some new types of objects.
A quasar-like discovery
The group of astronomers had detected in JWST images what appeared to be a lensed, quasar-like object from the early universe. Quasars are bright, active galactic nuclei: supermassive black holes at the centers of galaxies that are actively accreting material.
The James Webb Space Telescope is the next major space science observatory, designed to answer outstanding questions about the Universe and make groundbreaking discoveries in all fields of astronomy. Credit: Northrup Grumman
The power of gravitational lensing
The buildup of material in the black hole emits copious amounts of radiation that eclipses the host galaxy, giving rise to a compact, bright, star-like appearance. The JWST images in which Furtak and Zitrin identified the object were taken for the UNCOVER program (PIs: Ivo Labbé of Swinburne University of Technology and Rachel Bezanson of the University of Pittsburgh), which imaged the field of a galaxy cluster, Abell. 2744, at an unprecedented depth. Since the cluster contains large amounts of mass, it bends spacetime (or the paths of light rays traveling near it), effectively creating a gravitational lens. Gravitational lensing magnifies the background galaxies behind it and allows astronomers to observe even more distant galaxies than would otherwise be possible.
The red dot phenomenon
“We were very excited when JWST started sending its first data. We were scanning the data that came in for the UNCOVER program and three very compact but red objects stood out and caught our attention,” says Dr. Lukas Furtak, postdoctoral researcher at BGU and lead author of the discovery papers. “Its ‘red dot’ appearance immediately led us to suspect that it was a quasar-like object.”
Unraveling the mystery
Furtak and the UNCOVER group began investigating the object. “We used a numerical lens model we had built for the galaxy cluster to determine that the three red dots had to be multiple images of the same background source, seen when the Universe was only about 700 million years old,” says the professor. Zitrin. , BGU astronomer and one of the lead authors of the discovery papers.
A super massive advance
“Analysis of the object’s colors indicated that it was not a typical star-forming galaxy. This further supports the supermassive black hole hypothesis,” says Professor Rachel Bezanson of the University of Pittsburgh and co-director of the UNCOVER program. “Along with its compact size, it became clear that it was probably a supermassive black hole, although it was still different from other quasars found in those early days,” Professor Bezanson added. The discovery of the uniquely red and compact object was published last year in it Astrophysical diary. But that was only the beginning of the story.
Spectral perspectives and surprises
The team then acquired JWST/NIRSpec data from the three “red dot” images and analyzed the data. “The specters were just mind-blowing,” says Professor Ivo Labbé of Swinburne University of Technology and co-director of the UNCOVER programme. “By combining the signal from all three images along with lens magnification, the resulting spectrum is equivalent to ~1700 hours of observation by JWST on an unlensed object, making it the deepest spectrum JWST has ever seen.” obtained for a single object in the early universe,” says Professor Labbé.
“Using the spectra, we were able to not only confirm that the red compact object was a supermassive black hole and measure its exact redshift, but also obtain a solid estimate of its mass from the width of its emission lines,” says the author. principal, Dr. Furtak. “The gas orbits in the gravitational field of the black hole and reaches very high speeds not seen in other parts of galaxies. Due to Doppler shift, the light emitted by the accreting material is redshifted on one side and blueshifted on the other side, depending on its speed. This causes the emission lines in the spectrum to become broader.”
A darkened galaxy
But the measurement generated another surprise, published in Nature two weeks ago: The mass of the black hole appears to be excessively high compared to the mass of the host galaxy.
“All the light from that galaxy must fit within a small region the size of a modern star cluster. Magnifying the source’s gravitational lens gave us exquisite limits on size. Even cramming all the possible stars into such a small region, the black hole ends up being at least 1% of the total mass of the system,” says Professor Jenny Greene of Princeton University and one of the lead authors of the recent paper. “In fact, several other supermassive black holes in the early Universe have been found to show similar behavior, leading to some intriguing insights into the growth of black holes and their host galaxies, and the interaction between them, that are not is well understood.”
The cosmic chicken and egg dilemma
Astronomers don’t know whether these supermassive black holes grow, for example, from stellar debris or perhaps from material that collapsed directly into black holes in the early Universe.
“In a way, it’s the astrophysical equivalent of the chicken and egg problem,” says Professor Zitrin. “Currently we do not know which arose first: the galaxy or the black hole, how massive the first black holes were and how they grew.”
JWST Future Prospects
Since many more “little red dots” and other active galactic nuclei have been detected recently with JWST, hopefully we will have a better idea soon.
Reference: “A high black hole-to-host mass ratio in a lensed AGN in the early Universe” by Lukas J. Furtak, Ivo Labbé, Adi Zitrin, Jenny E. Greene, Pratika Dayal, Iryna Chemerynska, Vasily Kokorev, Tim B. Miller, Andy D. Goulding, Anna de Graaff, Rachel Bezanson, Gabriel B. Brammer, Sam E. Cutler, Joel Leja, Richard Pan, Sedona H. Price, Bingjie Wang, John R. Weaver, Katherine E. Whitaker, Hakim Atek, Ákos Bogdán, Stéphane Charlot, Emma Curtis-Lake, Pieter van Dokkum, Ryan Endsley, Robert Feldmann, Yoshinobu Fudamoto, Seiji Fujimoto, Karl Glazebrook, Stéphanie Juneau, Danilo Marchesini, Micheal V. Maseda, Erica Nelson, Pascal A. Oesch, Adèle Plat, David J. Setton, Daniel P. Stark, and Christina C. Williams, February 14, 2024, Nature.
DOI: 10.1038/s41586-024-07184-8