The 2010 interferometric imaging beauty contest

Malbet, Fabien; Cotton, W. D.; Duvert, G.; Lawson, Peter R.; Chiavassa, A.; Young, John S.; Baron, Fabien; Buscher, David F.; Sridharan, R.; Kloppenborg, Brian; Vannier, M.; Mugnier, Laurent M.

doi:10.1117/12.857066

Cited by 12 publications

(12 citation statements)

References 18 publications

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“…It is however important to carefully consider specific instrumental effects that could affect the visibility fluctuations. This can be already done with present day interferometers in addition to image reconstruction (Berger et al 2010;Malbet et al 2010) which eventually will be able to measure the size of granules directly. …”

Section: Visibility Curvesmentioning

confidence: 99%

Three-dimensional hydrodynamical simulations of red giant stars: semi-global models for interpreting interferometric observations

Chiavassa¹,

Collet²,

Casagrande³

et al. 2010

A&A

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Context. Theoretical predictions from models of red giant branch stars are a valuable tool for various applications in astrophysics ranging from galactic chemical evolution to studies of exoplanetary systems. Aims. We use the radiative transfer code Optim3D and realistic 3D radiative-hydrodynamical (RHD) surface convection simulations of red giants to explore the impact of granulation on interferometric observables. We assess how 3D simulations of surface convection can be validated against observations. Methods. We computed intensity maps for the 3D simulation snapshots in two filters, the optical at 5000 ± 300 Å and the K band 2.14±0.26 μm FLUOR filter, corresponding to the wavelength-range of instruments mounted on the CHARA interferometer. From the intensity maps, we constructed images of the stellar disks and account for center-to-limb variations. We then derived interferometric visibility amplitudes and phases. We study their behavior with position angle and wavelength, and compare them with CHARA observations of the red giant star HD 214868. Results. We provide average limb darkening coefficients for different metallicities and wavelengths ranges. We explain prospects for detecting and characterizing granulation and center-to-limb variations of red giant stars with today's interferometers. Regarding interferometric observables, we find that the effect of convective-related surface structures depends on metallicity and surface gravity. We provide theoretical closure-phases that should be incorporated into the analysis of red giant planet companion closure phase signals. We estimate 3D−1D corrections to stellar radii determination: 3D models are ∼3.5% smaller to ∼1% larger in the optical than 1D, and roughly 0.5 to 1.5% smaller in the infrared. Even if these corrections are small, they are needed to properly set the zero point of effective temperature scale derived by interferometry and to strengthen the confidence of existing red giant catalogs of calibrating stars for interferometry. Finally, we show that our RHD simulations provide an excellent fit to the red giant HD 214868 even though more observations are needed at higher spatial frequencies and shorter wavelength.

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Section: Visibility Curvesmentioning

confidence: 99%

Three-dimensional hydrodynamical simulations of red giant stars: semi-global models for interpreting interferometric observations

Chiavassa¹,

Collet²,

Casagrande³

et al. 2010

A&A

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“…Table 1 summarizes the features of the different algorithms that were specifically designed to cope with optical interferometry data. These algorithms are the main challengers of the Interferometric Imaging Beauty Contests which, every two years since 2004, quantitatively compares the results of various image synthesis methods on simulated optical interferometric data (Lawson et al, 2004(Lawson et al, , 2006Cotton et al, 2008;Malbet et al, 2010). Among these algorithms, BSMEM (Buscher, 1994;Baron and Young, 2008) and MiRA (Thiébaut, 2008) have repeatedly won the contest for data sets typical of next generation instruments.…”

Section: Imaging Algorithms and Their Applicationmentioning

confidence: 99%

“…Monnier et al, 2007;Le Bouquin et al, 2009;Schmitt et al, 2009;Kraus et al, 2009;Haubois et al, 2009;Kloppenborg et al, 2010;Millour et al, 2011). While model fitting of visibilities remains today the most accurate way to characterize an object brightness distribution, the technique has now reached a technical maturity level that opens new avenues for numerous astrophysical topics requiring milli-arcsecond model-independent imaging.…”

Section: Introductionmentioning

confidence: 99%

Imaging the heart of astrophysical objects with optical long-baseline interferometry

Berger

Malbet

Baron

et al. 2012

Astron Astrophys Rev

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The number of publications of aperture-synthesis images based on optical longbaseline interferometry measurements has recently increased due to easier access to visible and infrared interferometers. The interferometry technique has now reached a technical maturity level that opens new avenues for numerous astrophysical topics requiring milliarcsecond model-independent imaging. In writing this paper our motivation was twofold: 1) review and publicize emblematic excerpts of the impressive corpus accumulated in the field of optical interferometry image reconstruction; 2) discuss future prospects for this technique by selecting four representative astrophysical science cases in order to review the potential benefits of using optical long baseline interferometers.For this second goal we have simulated interferometric data from those selected astrophysical environments and used state-of-the-art codes to provide the reconstructed images that are reachable with current or soon-to-be facilities. The image reconstruction process was "blind" in the sense that reconstructors had no knowledge of the input brightness distributions. We discuss the impact of optical interferometry in those four astrophysical fields. We show that image reconstruction software successfully provides accurate morphological information on a variety of astrophysical topics and review the current strengths and weaknesses of such reconstructions. We investigate how to improve image reconstruction and the quality of the image possibly by upgrading the current facilities. We finally argue that optical interferometers and their corresponding instrumentation, existing or to come, with 6 to 10 telescopes, should be well suited to provide images of complex sceneries.

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“…Currently, the optical interferometer community have produced several algorithms to solve this problem, including the Building Block Method (Hofmann & Weigelt 1993), MACIM (Ireland et al 2006), MIRA (Thiébaut 2008), WISARD (Meimon et al 2008), and SQUEEZE ). See Malbet et al (2010) for a description of a recent blind imaging competition between some of these algorithms.…”

Section: Non-ideal Cases For Imagingmentioning

confidence: 99%

Radio and Optical Interferometry: Basic Observing Techniques and Data Analysis

Monnier

Allen

2013

Planets, Stars and Stellar Systems

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Astronomers usually need the highest angular resolution possible when observing celestial objects, but the blurring effect of diffraction imposes a fundamental limit on the image quality from any single telescope. Interferometry allows light collected at widely-separated telescopes to be combined in order to synthesize an aperture much larger than an individual telescope thereby improving angular resolution by orders of magnitude. Because diffraction has the largest effect for long wavelengths, radio and millimeter wave astronomers depend on interferometry to achieve image quality on par with conventional large-aperture visible and infrared telescopes. Interferometers at visible and infrared wavelengths extend angular resolution below the milli-arcsecond level to open up unique research areas in imaging stellar surfaces and circumstellar environments.In this chapter the basic principles of interferometry are reviewed with an emphasis on the common features for radio and optical observing. While many techniques are common to interferometers of all wavelengths, crucial differences are identified that will help new practitioners to avoid unnecessary confusion and common pitfalls. The concepts essential for writing observing proposals and for planning observations are described, depending on the science wavelength, the angular resolution, and the field of view required. Atmospheric and ionospheric turbulence degrades the longest-baseline observations by significantly reducing the stability of interference fringes. Such instabilities represent a persistent challenge, and the basic techniques of phase-referencing and phase closure have been developed to deal with them. Synthesis imaging with large observing datasets has become a routine and straightforward process at radio observatories, but remains challenging for optical facilities. In this context the commonly-used image reconstruction algorithms CLEAN and MEM are presented. Lastly, a concise overview of current facilities is included as an appendix.

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The 2010 interferometric imaging beauty contest

Cited by 12 publications

References 18 publications

Three-dimensional hydrodynamical simulations of red giant stars: semi-global models for interpreting interferometric observations

Three-dimensional hydrodynamical simulations of red giant stars: semi-global models for interpreting interferometric observations

Imaging the heart of astrophysical objects with optical long-baseline interferometry

Radio and Optical Interferometry: Basic Observing Techniques and Data Analysis

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