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

Abstract

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.

Compact Binary Progenitors of Short Gamma-Ray Bursts

“…So far, properties of the progenitors of SGRBs have been inferred by studying their redshift distribution, close environment, host galaxy types (Bloom et al 2006;Zhang et al 2009;Berger 2011), and by comparing those observations with predictions from population synthesis models (Perna & Belczynski 2002;Belczynski et al 2006;O'Shaughnessy et al 2008). In this Letter we make a connection between theory and observations, which allows us to directly probe the SGRB progenitors.…”

Computational Imaging for VLBI Image Reconstruction

“…• An improved forward model approximation that more accurately models spatial-frequency measurements, • A simpler problem formulation and optimization strategy to model the effects of atmospheric noise on VLBI data. Furthermore, current interferometry testing datasets are small and have noise properties unsuitable for radio wavelengths [3,6,26].…”

On the environment of short gamma-ray bursts

“…If we consider the prompt emission, negligible spectral lag (Norris, Marani & Bonnell 2000;Norris, Scargle & Bonnell 2001) and hard spectra (Kouveliotou et al 1993) are common for SGRBs. As opposed to LGRBs, for which the isotropic equivalent gamma-ray energy, E γ,iso , is of the order of 10 53 erg and for which the host galaxies are typically dwarf galaxies with high star formation rate (Fruchter et al 2006;Savaglio, Glazebrook & Le Borgne 2009), SGRBs are typically less energetic (E γ,iso is of the order of 10 49 -10 51 erg), they occur in both early-and late-type galaxies with lower star formation rate and are associated with an old stellar population (Nakar 2007;Berger 2009Berger , 2011. Furthermore, SGRBs have been found to be inconsistent with the E p,i −E iso correlation (Amati 2006;Amati et al 2007Amati et al , 2008.…”