arXiv subjects

Barnaby Norris

Publications and source records attributed to Barnaby Norris.

At least 19 recordsLinked to original sources

arXiv2026

The Photonic Lantern Nuller: from concept to laboratory and on-sky demonstrations

This thesis work presents the conceptual design and experimental characterization of the Photonic Lantern Nuller instrument, which uses a multimode-to-single-mode demultiplexing waveguide to cancel out starlight while maintaining planet light, allowing for the direct characterization of planets at a telescope's diffraction limit. The PLN was experimentally characterized in the lab, where it was further enhanced using common-path wavefront sensing and control techniques, and then demonstrated on sky at the Subaru Telescope. Highlights include measured in-lab null-depths of $\sim 10^{-4}$ in three out of four ports simultaneously and on-sky null-depths of approximately $\sim 10^{-1}$ (limited by jitter and atmospheric residuals). We provide an overview of these results and discuss avenues for future work.

astro-ph.IM↗

arXiv2026

Hector Galaxy Survey: Falling in Between - Infalling Galaxies in the Midst of the Abell 3667 Merger

Whether cluster mergers enhance ram pressure stripping (RPS) and accelerate member galaxy evolution remains an open question. Here, we investigate galaxy populations in the nearby merging cluster Abell 3667 ($z\simeq0.0553$) using spatially resolved data from the Hector Galaxy Survey. We define an RPS sample combining Hector-selected galaxies with ionised gas disturbances (e.g., asymmetric tails or truncated disks) and supplementary, optically identified jellyfish galaxies lacking Hector data. Most of the RPS sample ($\sim 71^{+10}_{-7}\%$; 20/28) lies within $R_{200}$, where the merger impact is greater. Most asymmetric galaxies ($\sim 73^{+14}_{-8}\%$; 11/15), especially those with extreme RPS signatures, are concentrated in the inner cluster ($R \lesssim 0.6\, R_{200}$), along the merger axis between two shock-tracing radio relics. These central asymmetric galaxies show two spatial and kinematic groups: one at the North-West (NW) subcluster, downstream of its radio relic in a region of high-velocity intracluster medium (ICM) bulk motion, with blueshifted line-of-sight velocities; and a mostly redshifted population near the main cluster (MC), which also shows a turbulent ICM. Despite their projected association with the MC core and NW substructure, both samples' velocities indicate they are not bound to them. Tail orientations give insight into orbital histories: NW tails point away from the cluster centre and often align with the merger axis, suggesting merger-driven stripping, while MC tails show neither pattern clearly. Tails are broadly westward, with MC tails tracing due west and NW tails shifted northwest, pointing to two distinct filamentary accretion events for the NW and MC populations. Together, our results indicate enhanced RPS in the heart of A3667, driven mainly by infalling galaxies accreted along nearby filaments interacting with the merger-driven turbulent environment.

astro-ph.GA↗

arXiv2026

FIRST-PL: Commissioning the first visible photonic lantern spectrograph for sub-diffraction-limit astronomy on Subaru/SCExAO

FIRST-PL (Fibered Imager foR a Single Telescope - Photonic Lantern) is a newly commissioned visible-light instrument on Subaru/SCExAO achieving spectroscopy below the diffraction limit. The instrument uses a Photonic Lantern (PL)-converting multimode fiber into 19 single-mode outputs-feeding a mid-resolution spectrograph (R 3000, 630-790 nm). On-sky performance demonstrates 40% injection efficiency at 680 nm (Strehl 30%) and 12x throughput improvement over single-mode fibers. Three operational modes enable spectro-astrometry (50 microarcseconds precision demonstrated on beta-CMi), image reconstruction, and high-contrast imaging. FIRST-PL represents a significant advancement in high-throughput photonic instrumentation.

astro-ph.IM↗

arXiv2026

Seidr update: photonic 'black magic' for high-contrast interferometry using kernel-nulling and photonic lanterns

Seidr is a new interferometric beam combiner within the Asgard Suite, utilizing infrastructure common to the BIFROST instrument at the Very Large Telescope Interferometer. Seidr combines hybrid mode-selective photonic lantern injection modules with a kernel-nulling photonic chip backend to enable deep H-band nulling for high-contrast studies of exoplanets, exomoons, and circumstellar dust. This instrument update summarizes Seidr's current design maturity and recent simulations of the point source - to - lantern outputs. We also outline progress on our neural network-based wavefront estimation scheme, which uses the photonic lantern outputs to sense phase fluctuations, designed to feed back to Baldr's deformable mirror, and improve nuller light injection.

physics.optics↗

arXiv2026

Overcoming the low signal-to-noise problem for hybrid mode-selective photonic lantern-based wavefront correction using machine learning

Hybrid mode-selective photonic lanterns transform an input complex point-spread function into several single-mode outputs, where a selected core feeds the fundamental mode to a photonic science instrument, while the remaining cores are used for wavefront sensing in a closed-loop adaptive optics system. A neural network maps the intensities of the wavefront sensing cores to an estimated wavefront correction, which is applied to an upstream deformable mirror. However, there exists a trade between maximizing the amount of light reserved for the photonic instrument and the reduced signal-to-noise ratios for the wavefront sensing cores. We explore wavefront correction for the Seidr instrument, a part of the Asgard Suite for the Very Large Telescope Interferometer. We evaluate different neural network architectures, comparing wavefront estimation performance for different wavefront error types, as a first step toward addressing the signal-to-noise trade-off. Results show transformer neural networks as a promising solution for temporal photonic lantern-based wavefront estimation.

physics.optics↗

arXiv2026

Hector Galaxy Survey: Optical IFU and Chandra Reveal a Low-Luminosity AGN Behind Extended LINER Emission

We present evidence that the Hector Galaxy Survey galaxy C901005481609968 ($z_{\rm cl}=0.0553$), which exhibits spatially extended LINER-like emission in optical integral-field spectroscopy (IFS), hosts a low-luminosity active galactic nucleus (LLAGN) that contributes substantially to its ionization budget. Although the galaxy is not selected as an AGN by mid-infrared AGN color criteria, archival Chandra data reveal a compact nuclear X-ray source with $\log L_{\rm X}\approx41.46$ erg/s, supporting the presence of an LLAGN. Spatially resolved emission-line diagnostics show LINER-like line ratios across most spaxels with $\mathrm{S/N} \geq 3$, while spatially resolved $\tau$ maps ($\tau \equiv Q_{\rm pAGB}/Q_{\rm req}$) indicate a widespread photon deficit ($\log\tau<0$ over most of the mapped region), even under the most optimistic pAGB normalizations, the nuclear region remains at $\tau < 1$. Line-ratio--kinematic tests find no evidence for shock-dominated excitation as the primary driver of the extended emission, although a localized or sub-dominant shock contribution cannot be ruled out with the present data. We use this galaxy as a pilot case because the combination of Hector IFS and an independent nuclear X-ray constraint provides a stringent validation of the spatially resolved photon-budget framework. Our results indicate that evolved stellar populations alone cannot account for the observed emission, that an additional nuclear ionizing source is required at least in the inner region, and that a weak LLAGN likely contributes to the ionizing budget, particularly in the inner region. Our results demonstrate that extended LINER-like emission can conceal a substantial LLAGN contribution even when traditional optical and infrared AGN indicators are weak, and that spatially resolved photon-budget tests combined with X-ray constraints can effectively reveal such hidden activity.

astro-ph.GA↗

arXiv2026

Combining spectroscopy and wavefront control at deep contrast with photonic lanterns

HWO aims to directly image objects orbiting Sun-like stars, using a 6-m telescope capable of high-contrast imaging ($10^{-10}$) and spectroscopy to search for biosignatures in planets located in the habitable zone. Recent laboratory demonstrations and ground-based telescope projects have shown the effectiveness of SMFs in spectroscopy, paving the way for SMF-fed spectrographs in future space missions like HWO. SMFs enhance spectral stability and reduce modal noise. HWO spectroscopy will need extended integration times, potentially lasting weeks. During these observations, the wavefront must be precisely measured and maintained to achieve the deep contrast and robust calibration of starlight contamination necessary for exoplanet characterization. We show that photonic lanterns (PLs) are ideally suited to meet these requirements. PLs are compact devices that couple light over a broader angular range than SMFs, ensuring higher throughput, converting a multimode input into multiple single-mode outputs. Positioned at the focal plane, they measure the complex amplitude of the coherent starlight within $\sim$ 2 l/D of the planet image, acting as compact wavefront sensors. Among the different variants of PLs that have emerged, the Hybrid-Mode Selective Photonic Lantern (HMSPL) is particularly attractive, as it directs object light into a central SMF feeding a mid-R spectrograph for exoplanet spectroscopy, while the adjacent SMFs route surrounding speckle light to a low-R spectrograph for rapid wavefront sensing. This dual function eliminates non-common path aberrations, optimizing injection efficiency and background suppression. We introduce HMSPL's dual role and planned tests at UTSA's high-contrast imaging lab and at SCExAO at the Subaru Telescope.

astro-ph.IM↗

arXiv2025

On-sky Demonstration of Subdiffraction-limited Astronomical Measurement Using a Photonic Lantern

Resolving fine details of astronomical objects provides critical insights into their underlying physical processes. This drives in part the desire to construct ever-larger telescopes and interferometer arrays and to observe at shorter wavelength to lower the diffraction limit of angular resolution. Alternatively, one can aim to overcome the diffraction limit by extracting more information from a single telescope's aperture. A promising way to do this is spatial mode-based imaging, which projects focal-plane field onto a set of spatial modes before detection, retaining focal-plane phase information crucial at small angular scales but typically lost in intensity imaging. However, the practical implementation of mode-based imaging in astronomy from the ground has been challenged by atmospheric turbulence. Here, we present the first on-sky demonstration of a subdiffraction-limited, mode-based measurement using a photonic lantern (PL)-fed spectrometer installed on the SCExAO instrument at the Subaru Telescope. We introduce a novel calibration strategy that mitigates time-varying wavefront error and misalignment effects, leveraging simultaneously recorded focal-plane images and using a spectral-differential technique that self-calibrates the data. Observing the classical Be star $\beta$ CMi, we detected spectral-differential spatial signals and reconstructed images of its H$\alpha$-emitting disk. We achieved an unprecedented H$\alpha$ photocenter precision of 50$\mu$as in about 10-minute observation with a single telescope, measuring the disk's near-far side asymmetry for the first time. This work demonstrates the high precision, efficiency, and practicality of photonic mode-based imaging techniques to recover subdiffraction-limited information, opening new avenues for high angular resolution spectroscopic studies in astronomy.

astro-ph.IM↗

arXiv2025

Dynamical Analysis of the HD 169142 Planet-Forming Disk: Twelve Years of High-Contrast Polarimetry

We present a dynamical analysis of the HD 169142 planet-forming disk based on high-contrast polarimetric imaging over a twelve-year observational period, offering insights into its disk evolution and planet-disk interactions. This study explores the evolution of scattered-light features and their relationship with millimeter continuum emission. Archival visible-to-near-infrared scattered-light observations from NACO, SPHERE, and GPI combined with new observations from SCExAO reveal persistent non-axisymmetric structures in both the inner and outer rings of the disk. Through Keplerian image transformations and phase cross-correlation techniques, we show that the azimuthal brightness variations in the inner ring follow the local Keplerian velocity, suggesting these are intrinsic disk features rather than planet-induced spirals or shadows. The motion of the outer ring is weakly detected, requiring a longer observational baseline for further confirmation. Comparing scattered-light features with ALMA 1.3 mm-continuum data, we find that the scattered light traces the edges of dust structures in the inner ring, indicating complex interactions and a leaky dust trap around the water-ice snowline. These findings highlight the capability of long-term monitoring of circumstellar disks to distinguish planetary influences from Keplerian disk dynamics.

astro-ph.EP↗

arXiv2025

PIRATES -- a machine-learning framework for polarized, interferometric image reconstruction

Optical interferometric image reconstruction is a challenging, ill-posed optimization problem which usually relies on heavy regularization for convergence. Conventional algorithms regularize in the pixel domain, without cognizance of spatial relationships or physical realism, with limited utility when this information is needed to reconstruct images. Here we present PIRATES (Polarimetric Image Reconstruction AI for Tracing Evolved Structures), the first image reconstruction algorithm for optical polarimetric interferometry. PIRATES has a dual structure optimized for parsimonious reconstruction of high fidelity polarized images and accurate reproduction of interferometric observables. The first stage, a convolutional neural network (CNN), learns a physically meaningful prior of self-consistent polarized scattering relationships from radiative transfer images. The second stage, an iterative fitting mechanism, uses the CNN as a prior for subsequent refinement of the images with respect to their polarized interferometric observables. Unlike the pixel-wise adjustments of traditional image reconstruction codes, PIRATES reconstructs images in a latent feature space, imparting a structurally derived implicit regularization. We demonstrate that PIRATES can reconstruct high fidelity polarized images of a broad range of complex circumstellar environments, in a physically meaningful and internally consistent manner, and that latent space regularization can effectively regularize reconstructed images in the presence of realistic noise.

astro-ph.IM↗

arXiv2025

GRIP: a generic data reduction package for nulling interferometry

Nulling interferometry is a powerful observing technique to study exoplanets and circumstellar dust at separations too small for direct imaging with single-dish telescopes. With recent photonics developments and the near-future ground-based instrumental projects, it bears the potential to detect young giant planets near the snow lines of their host stars. The observable quantity of a nulling interferometer is called the null depth, its precise measurement and calibration remain challenging against instrument and atmospheric noise. Null self-calibration is a method aiming to model the statistical distribution of the nulled signal. It has proven to be more sensitive and accurate than average-based data reduction methods in nulling interferometry. The variety of existing and upcoming of nullers raises the issue of consistency of the calibration process, structure of the data and the ability to reduce archived data on the long term. It has also led to many different implementations of the Null self-calibration method. In this article, we introduce GRIP: the first open-source toolbox to reduce nulling data with enhanced statistical self-calibration methods from any nulling interferometric instrument within a single and consistent framework. Astrophysical results show good consistency with two published GLINT and LBTI datasets and confirm nulling precision down to a few 10$^{-4}$.

astro-ph.IM↗

arXiv2025

Experimental and on-sky demonstration of spectrally dispersed wavefront sensing using a photonic lantern

Adaptive optics systems are critical in any application where highly resolved imaging or beam control must be performed through a dynamic medium. Such applications include astronomy and free-space optical communications, where light propagates through the atmosphere, as well as medical microscopy and vision science, where light propagates through biological tissue. Recent works have demonstrated common-path wavefront sensors for adaptive optics using the photonic lantern, a slowly varying waveguide that can efficiently couple multi-moded light into single-mode fibers. We use the SCExAO astrophotonics platform at the 8-m Subaru Telescope to show that spectral dispersion of lantern outputs can improve correction fidelity, culminating with an on-sky demonstration of real-time wavefront control. To our best knowledge, this is the first such result for either a spectrally dispersed or a photonic lantern wavefront sensor. Combined with the benefits offered by lanterns in precision spectroscopy, our results suggest the future possibility of a unified wavefront sensing spectrograph using compact photonic devices.

astro-ph.IM↗

arXiv2025

Implicit Electric Field Conjugation with the Photonic Lantern Nuller

The Photonic Lantern Nuller (PLN) is an instrument concept designed to characterize exoplanets within a single beam-width from its host star. The PLN leverages the spatial symmetry of a mode-selective photonic lantern (MSPL) to create nulled ports, which cancel out on-axis starlight but allow off-axis exoplanet light to couple. The null-depths are limited by wavefront aberrations in the system as well as by imperfections in the lantern. We show that the implicit electric field conjugation algorithm can be used to reduce the stellar coupling through the PLN by orders of magnitude while maintaining the majority of the off-axis light, leading to deeper null depths (~10^{-4}) and thus higher sensitivity to potential planet signals. We discuss a theory for the tradeoff we observed between the different ports, where iEFC improves the nulls of some ports at the expense of others, and show that targeting one port alone can lead to deeper starlight rejection through that port than when targeting all ports at once. We also observe different levels of stability depending on the port and discuss the implications for practically implementing this technique for science observations.

astro-ph.IM↗

arXiv2024

Spectral characterization of a 3-port photonic lantern for application to spectroastrometry

Spectroastrometry, which measures wavelength-dependent shifts in the center of light, is well-suited for studying objects whose morphology changes with wavelength at very high angular resolutions. Photonic lantern (PL)-fed spectrometers have potential to enable measurement of spectroastrometric signals because the relative intensities between the PL output SMFs contain spatial information on the input scene. In order to use PL output spectra for spectroastrometric measurements, it is important to understand the wavelength-dependent behaviors of PL outputs and develop methods to calibrate the effects of time-varying wavefront errors in ground-based observations. We present experimental characterizations of the 3-port PL on the SCExAO testbed at the Subaru Telescope. We develop spectral response models of the PL and verify the behaviors with lab experiments. We find sinusoidal behavior of astrometric sensitivity of the 3-port PL as a function of wavelength, as expected from numerical simulations. Furthermore, we compare experimental and numerically simulated coupling maps and discuss their potential use for offsetting pointing errors. We then present a method of building PL spectral response models (solving for the transfer matrices as a function of wavelength) using coupling maps, which can be used for further calibration strategies.

astro-ph.IM↗

arXiv2024

Visible-Light High-Contrast Imaging and Polarimetry with SCExAO/VAMPIRES

We present significant upgrades to the VAMPIRES instrument, a visible-light (600 nm to 800 nm) high-contrast imaging polarimeter integrated within SCExAO on the Subaru telescope. Key enhancements include new qCMOS detectors, coronagraphs, polarization optics, and a multiband imaging mode, improving sensitivity, resolution, and efficiency. These upgrades position VAMPIRES as a powerful tool for studying sub-stellar companions, accreting protoplanets, circumstellar disks, stellar jets, stellar mass-loss shells, and solar system objects. The instrument achieves angular resolutions from 17 mas to 21 mas and Strehl ratios up to 60\%, with 5$\sigma$ contrast limits of $10^{\text{-}4}$ at 0.1'' to $10^{\text{-}6}$ beyond 0.5''. We demonstrate these capabilities through spectro-polarimetric coronagraphic imaging of the HD 169142 circumstellar disk, ADI+SDI imaging of the sub-stellar companion HD 1160B, narrowband H$\alpha$ imaging of the R Aqr emission nebula, and spectro-polarimetric imaging of Neptune.

astro-ph.IM↗

arXiv2024

Spectroscopy using a visible photonic lantern at the Subaru telescope: Laboratory characterization and first on-sky demonstration on Ikiiki ({\alpha} Leo) and `Aua ({\alpha} Ori)

Photonic lanterns are waveguide devices enabling high throughput single mode spectroscopy and high angular resolution. We aim to present the first on-sky demonstration of a photonic lantern (PL) operating in visible light, to measure its throughput and assess its potential for high-resolution spectroscopy of compact objects. We used the SCExAO instrument (a double stage extreme AO system installed at the Subaru telescope) and FIRST mid-resolution spectrograph (R 3000) to test the visible capabilities of the PL on internal source and on-sky observations. The best averaged coupling efficiency over the PL field of view was measured at 51% +/- 10% with a peak at 80%. We also investigate the relationship between coupling efficiency and the Strehl ratio for a PL, comparing them with those of a single-mode fiber (SMF). Findings show that in the AO regime, a PL offers better coupling efficiency performance than a SMF, especially in the presence of low spatial frequency aberrations. We observed Ikiiki (alpha Leo - mR = 1.37) and `Aua (alpha Ori - mR = -1.17) at a frame rate of 200 Hz. Under median seeing conditions (about 1 arcsec measured in H band) and large tip/tilt residuals (over 20 mas), we estimated an average light coupling efficiency of 14.5% +/- 7.4%, with a maximum of 42.8% at 680 nm. We were able to reconstruct both star's spectra, containing various absorption lines. The successful demonstration of this device opens new possibilities in terms of high throughput single-mode fiber-fed spectroscopy in the Visible. The demonstrated on-sky coupling efficiency performance would not have been achievable with a single SMF injection setup under similar conditions, partly because the residual tip/tilt alone exceeded the field of view of a visible SMF (18 mas at 700 nm). Thus emphasizing the enhanced resilience of PL technology to such atmospheric disturbances. The additional

astro-ph.IM↗

arXiv2024

Design, scientific goals, and performance of the SCExAO survey for planets around accelerating stars

We describe the motivation, design, and early results for our 42-night, 125 star Subaru/SCExAO direct imaging survey for planets around accelerating stars. Unlike prior large surveys, ours focuses only on stars showing evidence for an astrometric acceleration plausibly due to the dynamical pull of an unseen planet or brown dwarf. Our program is motivated by results from a recent pilot program that found the first planet jointly discovered from direct imaging and astrometry and resulted in a planet and brown dwarf discovery rate substantially higher than previous unbiased surveys like GPIES. The first preliminary results from our program reveal multiple new companions; discovered planets and brown dwarfs can be further characterized with follow-up data, including higher-resolution spectra. Finally, we describe the critical role this program plays in supporting the Roman Space Telescope Coronagraphic Instrument, providing a currently-missing list of targets suitable for the CGI technological demonstration without which the CGI tech demo risks failure.

astro-ph.EP↗

arXiv2024

Spectral interferometric wavefront sensing: a solution for petalometry at Subaru/SCExAO

The petaling effect, induced by pupil fragmentation from the telescope spider, drastically affects the performance of high contrast instruments by inducing core splitting on the PSF. Differential piston/tip/tilt aberrations within each optically separated fragment of the pupil are poorly measured by commonly used Adaptive Optics (AO) systems. We here pursue a design of dedicated low-order wavefront sensor -- or petalometers -- to complement the main AO. Interferometric devices sense differential aberrations between fragments with optimal sensitivity; their weakness though is their limitation to wrapped phase measurements. We show that by combining multiple spectral channels, we increase the capture range for petaling aberrations beyond several microns, enough to disambiguate one-wave wrapping errors made by the main AO system. We propose here to implement a petalometer from the multi-wavelength imaging mode of the VAMPIRES visible-light instrument, deployed on SCExAO at the Subaru Telescope. The interferometric measurements obtained in four spectral channels through a 7 hole non-redundant mask allow us to effiiently reconstruct diffierential piston between pupil petals.

astro-ph.IM↗