Why chromatic imaging matters

Sánchez-Bermúdez, J.; Millour, F.; Baron, Fabien; Boekel, R. van; Bourgès, Laurent; Duvert, G.; Garcia, Paulo J. V.; Gomes, Nuno; Hofmann, K.-H.; Henning, Thomas; Isbell, J. W.; López, B.; Matter, A.; Pott, Jörg-Uwe; Schertl, D.; Thiébaut, Éric; Weigelt, G.; Young, John S.

doi:10.1007/s10686-018-9617-y

Cited by 8 publications

(3 citation statements)

References 54 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For this, mon- itoring observations with a few days to a week cadence are needed. Coordinated observations using near-and mid-IR interferometric instruments (e.g., GRAVITY and MATISSE) quasisimultaneously are also desired in order to reveal the chromatic nature of the asymmetry, and to improve the quality of the reconstructed images (Sanchez-Bermudez et al 2018). The assessment of the chromaticity can help to constrain the physical nature of the asymmetry.…”

Section: The Nature Of the Asymmetrymentioning

confidence: 99%

The asymmetric inner disk of the Herbig Ae star HD 163296 in the eyes of VLTI/MATISSE: evidence for a vortex?

Varga,

Hogerheijde,

van Boekel

et al. 2020

Preprint

View full text Add to dashboard Cite

Context. The inner few au region of planet-forming disks is a complex environment. High angular resolution observations have a key role in understanding the disk structure and the dynamical processes at work. Aims. In this study we aim to characterize the mid-infrared brightness distribution of the inner disk of the young intermediate-mass star HD 163296, from early VLTI/MATISSE observations, taken in the L-and N-bands. We put special emphasis on the detection of potential disk asymmetries. Methods. We use simple geometric models to fit the interferometric visibilities and closure phases. Our models include a smoothed ring, a flat disk with inner cavity, and a 2D Gaussian. The models can account for disk inclination and for azimuthal asymmetries as well. We also perform numerical hydro-dynamical simulations of the inner edge of the disk. Results. Our modeling reveals a significant brightness asymmetry in the L-band disk emission. The brightness maximum of the asymmetry is located at the NW part of the disk image, nearly at the position angle of the semimajor axis. The surface brightness ratio in the azimuthal variation is 3.5 ± 0.2. Comparing our result on the location of the asymmetry with other interferometric measurements, we confirm that the morphology of the r < 0.3 au disk region is time-variable. We propose that this asymmetric structure, located in or near the inner rim of the dusty disk, orbits the star. For the physical origin of the asymmetry, we tested a hypothesis where a vortex is created by Rossby wave instability, and we find that a unique large scale vortex may be compatible with our data. The half-light radius of the L-band emitting region is 0.33 ± 0.01 au, the inclination is 52 •+5 • −7 • , and the position angle is 143 • ± 3 • . Our models predict that a non-negligible fraction of the L-band disk emission originates inside the dust sublimation radius for µm-sized grains. Refractory grains or large ( 10 µm-sized) grains could be the origin for this emission. N-band observations may also support that the innermost disk (r 0.6 au) lacks small silicate grains, in agreement with our findings from L-band data.

show abstract

Section: The Nature Of the Asymmetrymentioning

confidence: 99%

The asymmetric inner disk of the Herbig Ae star HD 163296 in the eyes of VLTI/MATISSE: evidence for a vortex?

Varga,

Hogerheijde,

van Boekel

et al. 2020

Preprint

View full text Add to dashboard Cite

show abstract

“…Infrared interferometric imaging is an "ill-posed" problem (10), which means that we have significantly less data points than pixels in the image to recover. This is the reason why strong regularizers are necessary in the currently existing image reconstruction algorithms.…”

Section: Compressed Sensingmentioning

confidence: 99%

CASSINI-AUTOMAP: A novel software for interferometric image reconstruction

Sánchez-Bermúdez

Alberdi²,

Schödel³

et al. 2022

Optical and Infrared Interferometry and Imaging VIII

View full text Add to dashboard Cite

Interferometry delivers the highest angular resolution. It is being used extensively in radio astronomy and, since about a decade, it is becoming an important player in infrared astronomy. However, infrared interferometry is restricted to sparse arrays and no full-phase information is recovered. While imaging is arguably the most intuitive way to analyze interferometric data, recovering images from sparsely sampled visibilities is an "ill-posed" problem. The current algorithms work under the framework of using regularized minimization techniques. These algorithms strongly depend on the priors and hyperparameters pre-defined. This gives rise to ambiguities and artifacts in the interpretation of the images and limits their accuracy/precision as well as their signal-to-noise ratio if the priors/regularizers are not well-defined. Also, it means that imaging is the domain of a handful of highly experienced astronomers, thus keeping the interferometric community small. CASSINI-AUTOMAP aims at disrupting this situation by creating a novel framework for interferometric image reconstruction. This project is based on the exploitation of the compressibility of a signal (following the principles of theory of Compressed Sensing) with a novel optimization scheme supported by Neural Networks. In particular, we focus our efforts in designing a Neural Network with adaptive activation functions to find an optimal mapping system between the infrared interferometric data and the reconstructed images. The online adaptability of the Neural Network frees us from having to rely on strong priors, making the reconstructions more accurate and less dependent on users' inputs. Our preliminar network architecture has been tested with Sparse Aperture Masking (SAM) data taken with the infrared camera NACO at the Very Large Telescope and it demonstrates the potential and reliability of the algorithm by recovering the interferometric observables. Future improvements on the software aims at analyzing data from instruments like GRAVITY at the Very Large Telescope Interferometer or the Sparse Aperture Masking mode of the James Webb Space Telescope.

show abstract

“…3 Visible (MACAO) and infrared (CIAO) adaptive optics wavefront sensing for the UTs as well as a visible AO module NAOMI for the ATs: MACAO: https://www.eso.org/sci/facilities/paranal/telescopes/vlti/subsystems/ao.html, CIAO: http://www2.mpia-hd.mpg.de/GRAVITY/ NAOMI: https://www.eso.org/public/teles-instr/vlt/vlt-instr/naomi/ 4 https://www.eso.org/sci/facilities/paranal/telescopes/vlti/subsystems/control/fringecontrol.html 5 https://www.eso.org/sci/facilities/paranal/instruments/pionier.html The other key area of technological progress is in optimizing and automatizing the process of image reconstruction to derive model-independent images, and a reliable snapshot imaging mode (getting an image in less than a night), to eventually open the usage of arrays of 4-6 telescopes to the area of the time-domain astronomy [6]. Interferometric imaging hugely benefits from the availability of chromatic multibaseline datasets, as provided now by the VLTI 2nd generation instruments, and the coming years will augure a new era of interferometric imaging with reliable image quality benchmarking (Sanchez-Bermudez et al [10]).…”

Section: Before 2025: Parallel To the Construction Vlt 3rd Generationmentioning

confidence: 99%