Archival spectra of a lensed galaxy support two feeding black holes 175 parsecs apart
Astronomers report two feeding black holes 175 parsecs apart in a lensed galaxy at redshift 3.273, the most compact dual AGN known there. The spectroscopic case rests on one usable emission-line ratio. Two of the three lensed images match on it and the third is much lower.
The Scientist · Science desk
Bar comparison of estimated feeding-rate upper limits as a share of the maximum: image A about 47%, image B about 51%, image C about 4%.
Upper limit on feeding rate, % of maximum In % of maximum, about
| Item | Value | Claim |
|---|---|---|
| Image A | 47% of maximum, about | 12 |
| Image B | 51% of maximum, about | 12 |
| Image C | 4% of maximum, about | 12 |
What happened
- The team analysed archival 2018 VLT/MUSE spectra of MG B2016+112, a radio-loud active galaxy that a foreground galaxy lenses into three images, labelled A, B and C.
- Earlier radio and X-ray studies had already suggested two black holes about 175 parsecs apart, so this work was an independent test using resolved optical spectra of all three images.
- Mass estimates are at least 20 to 23 million solar masses for the hole behind images A and B, and at least 15 million solar masses for the hole behind C.
- Upper limits on feeding rates come out near 47% and 51% of the maximum for images A and B, and only about 4% for image C.
Why it matters
- capability Merger models predict dual active galactic nuclei, but close pairs are hard to resolve, so a lensed pair with similar masses gives an uncommon observational check on those models.
- contradiction Simulations that predict the lighter hole in a pair feeds faster do not match this system, where the lower-mass hole is the slower feeder.
- decision The authors want near-infrared observations to check the masses independently, and until those exist the merger reading leans on lower limits from a single emission line.
The method is a comparison across images. MG B2016+112 arrives as three lensed images, A, B and C [4], and the team extracted a spectrum for each, correcting for absorption by gas in our own galaxy and masking absorption from gas near the quasar [6]. Most emission-line ratios were too affected by absorption to compare, and one worked [7]. It matched for A and B and came out much lower for C [7]. We'd expect two images of one source to agree, and A and B do. "This provides strong spectroscopic evidence that C is associated with an ionizing source distinct from that producing A and B," the team writes in the paper [8].
That is one usable ratio in one system. We think the dual reading is well supported, because a separate line of evidence points the same way [5].
The masses are lower limits. They come from the width of the C IV line, and all three estimates landed in a similar mass range [9]. Lower limits do not show how far above them either hole sits, so they cannot be turned into a mass ratio. The team says similar masses fit two similar galaxies merging, each bringing its own black hole, and calls the result "consistent with the interpretation that the host galaxy underwent a major merger" [11].
The feeding rates are upper limits as well [12]. The estimates from A and B run roughly 12 to 13 times the estimate from C [18]. The team warns that C's rate depends on the magnification, and the one they used is an average that may be off [14].
The galaxy is seen when the universe was about 2 billion years old, and the pair sits about 570 light-years apart [1]. Phys.org's account calls it the most compact dual AGN known at this redshift [2]. The authors give the separation as projected: "At a projected separation of 175 pc at z = 3.273, this system represents the closest-separation confirmed dual AGN identified to date at such a high redshift," the researchers conclude [17]. The study was posted to the arXiv preprint server on Sept. 25 [3].
What to watch
- Near-infrared observations of MG B2016+112 that measure the two black hole masses independently of the C IV line.
- A revised magnification model for image C, which would show whether its roughly 4% feeding estimate and the conflict with simulations survive.
- A second emission-line ratio, usable despite the absorption, that separates image C from images A and B.
Clarity's read
What the record supports and how the coverage leans. The claims behind it follow.
Reality
- Evidence58
- Adoption
- Insufficient
- Hype gap+20
- Incentives
- Insufficient
- Confidence50
Claim ledger
Ranked by verification strength, evidence, and original report placement.
- [1]
Astronomers found two actively feeding supermassive black holes separated by 175 parsecs (570 light-years) in a galaxy seen when the universe was about 2 billion years old.
- [2]
The system, MG B2016+112, lies at a redshift of 3.273 and is the most compact dual AGN known at this redshift, according to phys.org's report.
- [3]
The study was posted to the arXiv preprint server on Sept. 25.
- [4]
The study, led by Jianghao Huyan and Julia M. Sisk-Reynes, analyzes archival VLT/MUSE spectra from 2018 of MG B2016+112, a radio-loud active galaxy at redshift 3.273 that a foreground galaxy gravitationally lenses into three images (A, B and C).
- [5]
Earlier radio and X-ray studies had suggested two black holes about 175 parsecs apart; the current study conducted an independent test using spatially resolved optical spectra of all three images.
- [6]
The team corrected the spectra for absorption from our galaxy's gas and masked absorption from gas near the quasar.
- [7]
Most spectral lines were too affected by absorption to compare their ratios, but one ratio worked; the numbers matched for images A and B, while image C had a much lower value.
- [8]
"This provides strong spectroscopic evidence that C is associated with an ionizing source distinct from that producing A and B," the team writes in the paper.
- [9]
The team estimated black hole masses from the width of the C IV line, and all three estimates turned out to be in a similar mass range.
- [10]
The black hole associated with images A and B has an estimated mass of at least 20 to 23 million solar masses, whereas the one associated with C has an estimated mass of at least 15 million solar masses.
- [11]
The team says similar masses fit the idea of two similar galaxies having merged, each bringing its own black hole, and that the result is "consistent with the interpretation that the host galaxy underwent a major merger."
- [12]
The team estimated upper limits on the black holes' feeding rates: about 47% and 51% of the maximum for images A and B, and only about 4% for image C.
- [13]
The feeding pattern supports the dual-black-hole picture but challenges simulations that predict the lighter black hole in a pair feeds faster: C is the lower-mass black hole and is feeding more slowly.
- [14]
The team warns the feeding rate for C could be uncertain because it depends on the magnification, and the magnification they considered is only an average and may be off.
- [15]
The researchers call for near-infrared observations to check the masses independently.
- [16]
Models predict that galaxy mergers drive gas onto central supermassive black holes, so merging galaxies should sometimes host dual active galactic nuclei (AGN); finding close pairs is hard because of observational limitations in distinguishing nearby bright spots.
- [17]
"At a projected separation of 175 pc at z = 3.273, this system represents the closest-separation confirmed dual AGN identified to date at such a high redshift," researchers conclude.
- [18]
The feeding-rate estimates from images A and B (about 47% and 51% of the maximum) are roughly 12 to 13 times the estimate from image C (about 4%).
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Sources
1 independent publisher whose own reporting we read for this story.
- phys.orgNew evidence points to two feeding black holes just 175 parsecs apart lurking in the early universe
1 article · October 14, 2026
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