The Cosmic Donut Returns: JWST Confirms the "Unified Model" of Active Galaxies by the Circinus Accretion Disk

Abstract

In January 2026, the field of extragalactic astrophysics witnessed a pivotal advancement with the release of new observations of the Circinus Galaxy by the James Webb Space Telescope (JWST). Utilizing the Aperture Masking Interferometry (AMI) mode of the Near-Infrared Imager and Slitless Spectrograph (NIRISS), a team led by Dr. Enrique Lopez-Rodriguez successfully resolved the parsec-scale structure of the galaxy's active nucleus. Contrary to prevailing models which posited that mid-infrared emission in such systems is dominated by polar outflows, the new data reveals that approximately 87% of the emission originates from a compact, equatorial accretion disk—the long-theorized "dusty torus." Conversely, dusty outflows contribute less than 1% to the infrared budget. This report provides an exhaustive analysis of these findings, detailing the interferometric methodology that effectively doubled the telescope's resolution, and exploring the profound implications for the Unified Model of Active Galactic Nuclei (AGN). By integrating these results with complementary ALMA radio data, we present a revised picture of the Circinus nucleus as a system dominated by stable accretion rather than radiative blow-out.

1. Introduction: The Black Hole Energy Crisis

For over half a century, the study of Active Galactic Nuclei (AGN) has been driven by a fundamental question: How do supermassive black holes, ranging from millions to billions of solar masses, acquire their fuel, and how does their immense energy output impact their host galaxies? The standard "Unified Model" of AGN posits a central black hole surrounded by a hot accretion disk, which is in turn obscured by a larger, doughnut-shaped structure of gas and dust known as the torus. This torus is the linchpin of AGN classification, explaining why some galaxies appear as "Type 1" (unobscured, viewing the central engine directly) and others as "Type 2" (obscured by the torus edge-on).¹

While this geometric model has successfully unified a diverse zoo of galactic phenomena, the precise dynamics of the torus have remained elusive. A critical debate in recent years has centered on the origin of the mid-infrared (MIR) light emitted by these systems. Is this light the thermal glow of the torus feeding the black hole, or is it the signature of "polar dust"—material being violently ejected in high-velocity winds?.⁴

Prior to 2026, observations of archetype galaxies like NGC 1068 suggested the latter: that the infrared energy budget was dominated by feedback-driven outflows.⁴ This implied that AGN were messy eaters, blowing away as much or more material than they consumed. However, the 2026 JWST investigation of the Circinus Galaxy has dramatically overturned this assumption for this class of object, providing the clearest evidence yet of a feeding-dominated system.¹

2. The Target: Circinus Galaxy (ESO 97-G13)

To test the physics of accretion, astronomers require a laboratory that is both active and accessible. The Circinus Galaxy, located approximately 13 million light-years (4.0 megaparsecs) away in the southern constellation of Circinus, serves as this ideal cosmic testbed.¹

2.1 Galactic Environment and Classification

Circinus is a massive spiral galaxy (Type SA(s)b) situated only 4 degrees below the plane of our own Milky Way. This proximity to the Galactic plane means Circinus is heavily obscured by foreground stars and dust, which historically delayed its detailed study until 1977.⁸ It is classified as a Seyfert 2 galaxy, meaning its central engine is obscured from our direct optical line of sight by significant columns of dust.²

Despite the obscuration, Circinus is a cauldron of activity. It features two prominent rings of star formation:

• Outer Ring: Spanning approximately 1,400 light-years, where gas is rapidly converting into stars.

• Inner Ring: A compact structure only 260 light-years across, encircling the active core.⁹

2.2 The Pre-Webb View

Before the JWST era, our understanding of Circinus was constructed from a composite of multi-wavelength data.

• Hubble Space Telescope (HST): Optical imaging revealed a classic "V-shape" or ionization cone. This is the region where ultraviolet radiation from the hidden black hole escapes through the hole of the torus, illuminating the gas in the galaxy's halo like a lighthouse beam.⁹

• Chandra X-ray Observatory: X-ray spectroscopy confirmed the nucleus is "Compton-thick," implying the obscuring torus has a column density high enough to scatter even high-energy X-rays. Chandra also detected shock-heated gas in the kiloparsec-scale lobes, evidence of long-term feedback activity.¹¹

• ALMA (Atacama Large Millimeter/submillimeter Array): Recent radio observations probed the cold molecular gas, identifying spiral arms feeding material inward at a rate of 0.3 to 7.5 solar masses per year.¹³

While these instruments mapped the surroundings of the black hole, the structure of the torus itself—a region only a few parsecs wide—remained unresolved, blurred by the diffraction limits of even the largest telescopes.

3. Methodology: Breaking the Diffraction Limit via the JWST

The primary obstacle in resolving the Circinus torus is the fundamental limit of optics. For a telescope with a primary mirror diameter D observing at a wavelength lambda, the smallest angular detail theta it can resolve is given by the Rayleigh criterion:

theta is approximately equal to 1.22 times lambda divided by D

For JWST observing in the mid-infrared (4.3 micrometers), the standard resolution is excellent but still insufficient to distinguish the torus from the surrounding starburst dust at a distance of 13 million light-years. To overcome this, the research team employed a technique known as Aperture Masking Interferometry (AMI).¹

3.1 The Non-Redundant Mask (NRM)

The AMI mode utilizes a specialized component within the NIRISS instrument: a "Non-Redundant Mask." This is an opaque plate positioned in the light path, punctuated by seven hexagonal holes (sub-apertures). Instead of using the full 6.5-meter mirror to form a direct image, the mask blocks most of the light, allowing only the beams from these seven holes to pass through.¹⁶

When light waves from these holes overlap on the detector, they create an interferogram—a complex pattern of bright and dark fringes caused by constructive and destructive interference. This is analogous to the classic double-slit experiment, but scaled up to seven apertures arranged in a specific 2D pattern.

3.2 Achieving "Super-Resolution"

The layout of the holes is mathematically "non-redundant," meaning that the distance and angle (the "baseline") between any pair of holes is unique. No two pairs are the same.

• Fourier Sampling: Because each baseline samples a unique spatial frequency, the resulting interference pattern contains precise information about the source's structure at different scales.

• Closure Phases: By analyzing the phases of the light waves around closed triangles of holes, astronomers can cancel out the blurring effects of minute optical errors or "jitter" in the telescope.

This technique effectively transforms JWST into an interferometric array, allowing it to resolve details as if it were a telescope with a diameter of roughly 13 meters—double its actual size. This "super-resolution" capability enabled the team to resolve features as small as 2 parsecs (roughly 6.5 light-years) in the Circinus core, a feat previously impossible for a single space telescope.¹⁵

3.3 Observation Parameters

The study, led by Principal Investigator Enrique Lopez-Rodriguez, observed the galaxy in three specific infrared filters designed to trace dust at different temperatures:

1. F380M (3.8 microns)

2. F430M (4.3 microns)

3. F480M (4.8 microns)

This marked the first time a high-contrast interferometric mode was used on an extragalactic source, pushing the instrument to its theoretical limits to detect the faint glow of the torus against the bright stellar background.¹

4. Results: The Anatomy of an Active Nucleus

The reconstructed images from the AMI data presented a view of the Circinus core that fundamentally alters our understanding of its energy budget.

4.1 Visualizing the Torus

The JWST images resolved a compact, elongated structure at the very center of the galaxy.

• The "Donut" Hole: For the first time, the "hole" of the torus—the central cavity where dust sublimates due to the intense heat of the black hole—was spatially resolved. The images show the inner face of the torus glowing brightly as it intercepts the radiation from the accretion disk.¹

• Dark Spots: Surrounding this bright inner ring are "dark spots." These represent the cooler, denser outer regions of the torus that are self-shadowed or absorb the infrared light, effectively silhouetting the outer ring against the background emission.¹

• Orientation: The structure aligns with the galaxy's geometry, with the "North" compass arrow pointing toward the 11 o'clock position and "East" toward 7 o'clock, confirming the physical orientation of the disk relative to the larger galactic spiral arms.¹⁶

4.2 The Quantitative Shift: Accretion vs. Outflow

The most consequential finding of the study is the quantitative breakdown of the mid-infrared emission. Previous models, heavily influenced by observations of other AGN like NGC 1068, predicted that a substantial fraction of the mid-IR light would come from "polar dust"—material entrained in outflows perpendicular to the disk.⁴

The JWST data for Circinus reveals a starkly different picture. The research team decomposed the infrared flux into three components:

Component	Description	Contribution to Mid-IR Flux
The Torus (Disk)	Compact, equatorial dust structure feeding the black hole.	~87%
Extended Emission	Dust in the host galaxy/starburst regions (uncollimated).	~12%
Polar Outflows	Hot dust entrained in the high-velocity winds.	< 1%

Table 1: Decomposition of Mid-Infrared Emission in the Circinus Galaxy Core.¹

This distribution indicates that the Circinus AGN is accretion-dominated in the infrared. The vast majority of the hot dust is located in the feeding reservoir, not the exhaust plume.

4.3 Coupling with Radio Data

Integrating these findings with recent radio data from ALMA (Isbell et al., 2025) provides a complete view of the mass flow. ALMA traces the cold molecular gas, which is seen flowing inward along spiral arms at a rate of 0.3 to 7.5 solar masses per year.¹³ The JWST data confirms that this material successfully accumulates in the hot torus observed at 4.3 microns. The extremely low fraction of dust in the outflow (<1%) suggests that while gas may be ejected (as seen in ionized optical lines), the dust is either destroyed, left behind, or too cool to emit in the mid-infrared.¹⁹

5. Discussion: Implications for the Unified Model

The resolution of the Circinus core serves as a critical calibration point for the Unified Model of AGN.

5.1 The "Clumpy" vs. "Smooth" Torus

Theoretical models have long debated whether the torus is a smooth, continuous distribution of gas or a chaotic swarm of "clumps." The smoothness of the resolved image—showing a coherent disk structure rather than scattered blobs—suggests a high "filling factor." While the material is likely clumpy on small scales to maintain vertical stability against gravity, on the macroscopic scales resolved by JWST, it behaves as a coherent, rotationally supported disk. This supports the "dynamical torus" model, where the structure is essentially a puffed-up extension of the galactic disk.³

5.2 Rethinking Feedback Efficiency

"AGN Feedback" is the mechanism by which supermassive black holes regulate the growth of their host galaxies, blowing away gas to quench star formation. The discovery that the dusty outflow component in Circinus is negligible (<1% of emission) implies that, at least in this specific phase of activity, the radiative driving of dust is inefficient.

This contrasts with the "blow-out" phase seen in more luminous quasars. It suggests that feedback efficiency may be highly dependent on the Eddington ratio (the accretion rate relative to the maximum limit). Circinus, with a moderate accretion rate, may lack the radiation pressure to lift heavy dust grains out of the gravitational well, resulting in a "fountain" where gas rises but dust stays bound to the disk.²¹

5.3 A Tale of Two Galaxies: Circinus vs. NGC 1068

The findings highlight the diversity of AGN engines. In NGC 1068, interferometric studies suggested a dominance of polar winds.⁴ In Circinus, JWST confirms a dominance of the equatorial torus.

• Scenario A: The difference is intrinsic. NGC 1068 is intrinsically more luminous, driving stronger winds that dominate the IR signal.

• Scenario B: The difference is observational. Previous ground-based interferometry of NGC 1068 may have struggled to separate the compact torus from the wind due to atmospheric noise, whereas the space-based stability of JWST/NIRISS allows for a cleaner separation.

Future observations of NGC 1068 with the same AMI mode on JWST will be crucial to determine if the "polar dust" paradigm holds up under space-based scrutiny.¹

6. Conclusion and Future Outlook

The JWST observations of the Circinus Galaxy represent a triumph of experimental astrophysics. By leveraging the Aperture Masking Interferometry technique, astronomers have effectively bypassed the diffraction limits of the 6.5-meter telescope, peering into the very throat of a supermassive black hole with a resolution of 2 parsecs.

The scientific yield is a fundamental revision of the energy budget for this nearest active galaxy. The revelation that 87% of the mid-infrared light comes from the feeding torus—and less than 1% from the outflow—paints a picture of a "calm" feeder, where the central engine is efficiently fueled by a stable reservoir of dust and gas. This contradicts recent trends that emphasized the role of dusty winds in Type 2 Seyferts, suggesting instead that the "donut" model is not only geometrically correct but energetically dominant.

As lead author Enrique Lopez-Rodriguez notes, "We need a statistical sample of black holes... to understand how mass in their accretion disks and their outflows relate to their power".¹ With proposals already underway to apply this technique to a dozen more nearby AGN, the Circinus result is likely the first chapter in a new "Atlas of Active Nuclei," one that will map the metabolic processes of the universe's most powerful engines with unprecedented clarity.

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