M. C. Wyatt’s research while affiliated with University of Cambridge and other places

We present aperture masking interferometry (AMI) observations of the star HIP 65426 at 3.8 μ m, as part of the JWST Direct Imaging Early Release Science program, obtained using the Near Infrared Imager and Slitless Spectrograph instrument. This mode provides access to very small inner working angles (even separations slightly below the Michelson limit of 0.5 λ / D for an interferometer), which are inaccessible with the classical inner working angles of the JWST coronagraphs. When combined with JWST’s unprecedented infrared sensitivity, this mode has the potential to probe a new portion of parameter space across a wide array of astronomical observations. Using this mode, we are able to achieve a 5 σ contrast of Δ m F380M ∼ 7.62 ± 0.13 mag relative to the host star at separations ≳0 . ″ 07 , and the contrast deteriorates steeply at separations ≲0 . ″ 07. However, we detect no additional companions interior to the known companion HIP 65426b (at separation ∼0 . ″ 82 or 8 7 − 31 + 108 au ). Our observations thus rule out companions more massive than 10–12 M Jup at separations ∼10–20 au from HIP 65426, a region out of reach of ground- or space-based coronagraphic imaging. These observations confirm that the AMI mode on JWST is sensitive to planetary mass companions at close-in separations (≳0 . ″ 07), even for thousands of more distant stars at ∼100 pc, in addition to the stars in the nearby young moving groups and associations, as stated in previous works. This result will allow the planning and successful execution of future observations to probe the inner regions of nearby stellar systems, opening an essentially unexplored parameter space.

Recent JWST observations of the Fomalhaut debris disk have revealed a significant abundance of dust interior to the outer planetesimal belt, raising questions about its origin and maintenance. In this study, we apply an analytical model to the Fomalhaut system, that simulates the dust distribution interior to a planetesimal belt, as collisional fragments across a range of sizes are dragged inward under Poynting-Robertson (PR) drag. We generate spectral energy distributions and synthetic JWST/MIRI images of the model disks, and perform an extensive grid search for particle parameters—pertaining to composition and collisional strength—that best match the observations. We find that a sound fit can be found for particle properties that involve a substantial water ice component, around 50–80 % by total volume, and a catastrophic disruption threshold, $Q_\mathrm{D}^\star$, at a particle size of D ≈ 30 μm of (2–4) × 106 erg g−1. Based on the expected dynamical depletion of migrating dust by an intervening planet we discount planets with masses >1 MSaturn beyond ∼50 au in the extended disk, though a planet shepherding the inner edge of the outer belt of up to ∼2 MSaturn is reconcilable with the PR-drag-maintained disk scenario, contingent upon higher collisional strengths. These results indicate that PR drag transport from the outer belt alone can account for the high interior dust contents seen in the Fomalhaut system, which may thus constitute a common phenomenon in other belt-bearing systems. This establishes a framework for interpreting mid-planetary system dust around other stars, with our results for Fomalhaut providing a valuable calibration of the models.

In addition to planets and other small bodies, stellar systems will likely also host exozodiacal dust, or exozodi. This warm dust primarily resides in or near the habitable zone of a star, and scatters stellar light in visible to NIR wavelengths, possibly acting as a spatially inhomogeneous fog that can impede our ability to detect and characterize Earth-like exoplanets. By improving our knowledge of exozodi in the near term with strategic precursor observations and model development, we may be able to mitigate these effects to support a future search for signs of habitability and life with a direct imaging mission. This white paper introduces exozodi, summarizes its impact on directly imaging Earth-like exoplanets, and outlines several key knowledge gaps and near-term solutions to maximize the science return of future observations.

Recent JWST observations of the Fomalhaut debris disk have revealed a significant abundance of dust interior to the outer planetesimal belt, raising questions about its origin and maintenance. In this study, we apply an analytical model to the Fomalhaut system, that simulates the dust distribution interior to a planetesimal belt, as collisional fragments across a range of sizes are dragged inward under Poynting-Robertson (PR) drag. We generate spectral energy distributions and synthetic JWST/MIRI images of the model disks, and perform an extensive grid search for particle parameters -- pertaining to composition and collisional strength -- that best match the observations. We find that a sound fit can be found for particle properties that involve a substantial water ice component, around 50--80% by total volume, and a catastrophic disruption threshold, $Q_D^\star$, at a particle size of $D\!\approx\!30\,$um of 2--4$\,\times\,10^6\,$erg/g. Based on the expected dynamical depletion of migrating dust by an intervening planet we discount planets with masses $>1\,M_\mathrm{Saturn}$ beyond $\sim50\,$au in the extended disk, though a planet shepherding the inner edge of the outer belt of up to $\sim2\,M_\mathrm{Saturn}$ is reconcilable with the PR-drag-maintained disk scenario, contingent upon higher collisional strengths. These results indicate that PR drag transport from the outer belt alone can account for the high interior dust contents seen in the Fomalhaut system, which may thus constitute a common phenomenon in other belt-bearing systems. This establishes a framework for interpreting mid-planetary system dust around other stars, with our results for Fomalhaut providing a valuable calibration of the models.

This Letter reports 12 novel spectroscopic detections of warm circumstellar dust orbiting polluted white dwarfs using the JWST Mid-Infrared Instrument (MIRI). The disks span 2 orders of magnitude in fractional infrared brightness and more than double the number of white dwarf dust spectra available for mineralogical study. Among the highlights are (i) the two most subtle infrared excesses yet detected, (ii) the strongest silicate emission features known for any debris disk orbiting any main-sequence or white dwarf star, (iii) one disk with a thermal continuum but no silicate emission, and (iv) three sources with likely spectral signatures of silica glass. The near ubiquity of solid-state emission requires small dust grains that are optically thin and thus must be replenished on year-to-decade timescales by ongoing collisions. The disk exhibiting a featureless continuum can only be fit by dust temperatures in excess of 2000 K, implying highly refractory material comprised of large particles, or non-silicate mineral species. If confirmed, the glassy silica orbiting three stars could be indicative of high-temperature processes and subsequent rapid cooling, such as occur in high-velocity impacts or vulcanism. These detections have been enabled by the unprecedented sensitivity of MIRI low-resolution spectrometer spectroscopy and highlight the capability and potential for further observations in future cycles.

Debris disks common around Sun-like stars carry dynamical imprints in their structure that are key to understanding the formation and evolution history of planetary systems. In this paper, we extend an algorithm (rave) originally developed to model edge-on disks to be applicable to disks at all inclinations. The updated algorithm allows for non-parametric recovery of the underlying (i.e., deconvolved) radial profile and vertical height of optically thin, axisymmetric disks imaged in either thermal emission or scattered light. Application to simulated images demonstrates that the de-projection and deconvolution performance allows for accurate recovery of features comparable to or larger than the beam or PSF size, with realistic uncertainties that are independent of model assumptions. We apply our method to recover the radial profile and vertical height of a sample of 18 inclined debris disks observed with ALMA. Our recovered structures largely agree with those fitted with an alternative visibility-space de-projection and deconvolution method (frank). We find that for disks in the sample with a well-defined main belt, the belt radius, fractional width and fractional outer edge width all tend to increase with age, but do not correlate in a clear or monotonic way with dust mass or stellar temperature. In contrast, the scale height aspect ratio does not strongly correlate with age, but broadly increases with stellar temperature. These trends could reflect a combination of intrinsic collisional evolution in the disk and the interaction of perturbing planets with the disk’s own gravity.

Debris disks common around Sun-like stars carry dynamical imprints in their structure that are key to understanding the formation and evolution history of planetary systems. In this paper, we extend an algorithm (rave) originally developed to model edge-on disks to be applicable to disks at all inclinations. The updated algorithm allows for non-parametric recovery of the underlying (i.e., deconvolved) radial profile and vertical height of optically thin, axisymmetric disks imaged in either thermal emission or scattered light. Application to simulated images demonstrates that the de-projection and deconvolution performance allows for accurate recovery of features comparable to or larger than the beam or PSF size, with realistic uncertainties that are independent of model assumptions. We apply our method to recover the radial profile and vertical height of a sample of 18 inclined debris disks observed with ALMA. Our recovered structures largely agree with those fitted with an alternative visibility-space de-projection and deconvolution method (frank). We find that for disks in the sample with a well-defined main belt, the belt radius, fractional width and fractional outer edge width all tend to increase with age, but do not correlate in a clear or monotonic way with dust mass or stellar temperature. In contrast, the scale height aspect ratio does not strongly correlate with age, but broadly increases with stellar temperature. These trends could reflect a combination of intrinsic collisional evolution in the disk and the interaction of perturbing planets with the disk's own gravity.

The Herschel open-time key program Disc Emission via a Bias-free Reconnaissance in the Infrared and Sub-millimeter (DEBRIS) is an unbiased survey of the nearest ~100 stars for each stellar type A-M observed with a uniform photometric sensitivity to search for cold debris disks around them. The analysis of the Photoconductor Array Camera and Spectrometer (PACS) photometric observations of the 94 DEBRIS M dwarfs of this program is presented in this paper, following upon two companion papers on the DEBRIS A-star and FGK-star subsamples. In the M-dwarf subsample, two debris disks have been detected, around the M3V dwarf GJ581 and the M4V dwarf FomalhautC (LP876-10). This result gives a disk detection rate of 2.1^{+2.7}_{-0.7}% at the 68% confidence level, significantly less than measured for earlier stellar types in the DEBRIS program. However, we show that the survey of the DEBRIS M-dwarf subsample is about ten times shallower than the surveys of the DEBRIS FGK subsamples when studied in the physical parameter space of the disk's fractional dust luminosity versus blackbody radius. Furthermore, had the DEBRIS K-star subsample been observed at the same shallower depth in this parameter space, its measured disk detection rate would have been statistically consistent with the one found for the M-dwarf subsample. Hence, the incidence of debris disks does not appear to drop from the K subsample to the M subsample of the DEBRIS program, when considering disks in the same region of physical parameter space. An alternative explanation is that the only two bright disks discovered in the M-dwarf subsample would not, in fact, be statistically representative of the whole population.

This letter reports 12 novel spectroscopic detections of warm circumstellar dust orbiting polluted white dwarfs using JWST MIRI. The disks span two orders of magnitude in fractional infrared brightness and more than double the number of white dwarf dust spectra available for mineralogical study. Among the highlights are: i) the two most subtle infrared excesses yet detected, ii) the strongest silicate emission features known for any debris disk orbiting any main-sequence or white dwarf star, iii) one disk with a thermal continuum but no silicate emission, and iv) three sources with likely spectral signatures of silica glass. The near ubiquity of solid-state emission requires small dust grains that are optically thin, and thus must be replenished on year-to-decade timescales by ongoing collisions. The disk exhibiting a featureless continuum can only be fit by dust temperatures in excess of 2000K, implying highly refractory material comprised of large particles, or non-silicate mineral species. If confirmed, the glassy silica orbiting three stars could be indicative of high-temperature processes and subsequent rapid cooling, such as occur in high-velocity impacts or vulcanism. These detections have been enabled by the unprecedented sensitivity of MIRI LRS spectroscopy and highlight the capability and potential for further observations in future cycles.

The Herschel open-time key program Disc Emission via a Bias-free Reconnaissance in the Infrared and Sub-millimeter (DEBRIS) is an unbiased survey of the nearest ∼ 100 stars for each stellar type A-M observed with a uniform photometric sensitivity to search for cold debris disks around them. The analysis of the Photoconductor Array Camera and Spectrometer (PACS) photometric observations of the 94 DEBRIS M dwarfs of this program is presented in this paper, following upon two companion papers on the DEBRIS A-star and FGK-star subsamples. In the M-dwarf subsample, two debris disks have been detected, around the M3V dwarf GJ 581 and the M4V dwarf Fomalhaut C (LP 876-10). This result gives a disk detection rate of 2.1^ % at the 68% confidence level, significantly less than measured for earlier stellar types in the DEBRIS program. However, we show that the survey of the DEBRIS M-dwarf subsample is about ten times shallower than the surveys of the DEBRIS FGK subsamples when studied in the physical parameter space of the disk's fractional dust luminosity versus blackbody radius. Furthermore, had the DEBRIS K-star subsample been observed at the same shallower depth in this parameter space, its measured disk detection rate would have been statistically consistent with the one found for the M-dwarf subsample. Hence, the incidence of debris disks does not appear to drop from the K subsample to the M subsample of the DEBRIS program, when considering disks in the same region of physical parameter space. An alternative explanation is that the only two bright disks discovered in the M-dwarf subsample would not, in fact, be statistically representative of the whole population.