Astronomical instrumentation

Abstract:

More than a century ago, Albert Einstein presented his general theory of gravitation (GR) to the Prussian Academy of Sciences. One of the predictions of the theory is that not only particles and objects with mass, but also the quanta of light, photons, are tied to the curvature of space-time, and thus to gravity. There must be a critical compactness, above which photons cannot escape. These are black holes (henceforth BH). It took fifty years after the theory was announced before possible candidate objects were identified by observational astronomy. And another fifty years have passed, until we finally have in hand detailed and credible experimental evidence that BHs of 10 to 10^10 times the mass of the Sun exist in the Universe. Three very different experimental techniques, but all based on Michelson interferometry or Fourier-inversion spatial interferometry have enabled the critical experimental breakthroughs. It has now become possible to investigate the space-time structure in the vicinity of the event horizons of BHs. We briefly summarize these interferometric techniques, and discuss the spectacular recent improvements achieved with all three techniques. Finally, we sketch where the path of exploration and inquiry may go on in the next decades.Comment: 50 pages, accepted to The Astronomy and Astrophysics Revie

Abstract:

MAJIS (Moons And Jupiter Imaging Spectrometer) is one of the key scientific instruments on board the Jupiter ICy Moons Explorer (JUICE), the next mission to the Jovian system. A reliable determination of H(USD)_{2}(USD)O and CH(USD)_{4}(USD) densities in the vertical structure and distribution of Jupiter's atmosphere is one of our main goals. In order to achieve this, we implemented the current knowledge of physical and chemical properties of Jupiter in ASIMUT-ALVL to perform simulations with different viewing geometries of the MAJIS instrument from 0.5$\mu$m to 2.5(USD)\mu(USD)m. ASIMUT-ALVL is a Radiative Transfer (RT) code developed at BIRA-IASB that has been extensively used to characterize Mars and Venus atmospheres.\footnote{Vandaele, A.C., et al., Optics Express. 2013, 21(18), 21148}(USD)^{,}(USD)/footnote{Vandaele, A.C., et al., Icarus. 2017, 295, 1-15.} Our simulations are benchmarked to those from KOPRA, another RT software previously used for the study of Titan, Mars and Jupiter.\footnote{López-Puertas, M., et al., The Astronomical Journal. 2018, 156.4, 169.} The next step is to validate our model against Jupiter observational data to finally assess the performances of the MAJIS VIS-NIR channel\footnote{Cisneros-González, M.E., et al., SPIE Astronomical Telescopes and Instrumentation. 2020, 114431L.} to characterize the vertical structure of the Jovian atmosphere.\footnote{\textit{This project acknowledges the funding provided by the Belgian National Scientific Research Fund (FNRS by its acronym in french) through the Aspirant-Renewal Grant ``34828872 MAJIS detectors and Impact on Science".}

Abstract:

The upcoming WEAVE-QSO survey will target a high density of quasars over a large area, enabling the reconstruction of the 3D density field through Lyman-훼 tomography over unprecedented volumes smoothed on intermediate cosmological scales (≈ 16 Mpc/h). We produce mocks of the Lyman-훼 forest using LyMAS, and reconstruct the 3D density field between sightlines through Wiener filtering in a configuration compatible with the future WEAVE-QSO observations. The fidelity of the reconstruction is assessed by measuring one- and two-point statistics from the distribution of critical points in the cosmic web. In addition, initial Lagrangian statistics are predicted from first principles, and measurements of the connectivity of the cosmic web are performed. The reconstruction captures well the expected features in the auto- and cross-correlations of the critical points. This remains true after a realistic noise is added to the synthetic spectra, even though sparsity of sightlines introduces systematics, especially in the cross-correlations of points with mixed signature. Specifically, the most striking clustering features involving filaments and walls could be measured with up to 4 sigma of significance with a WEAVE-QSO-like survey. Moreover, the connectivity of each peak identified in the reconstructed field is globally consistent with its counterpart in the original field, indicating that the reconstruction preserves the geometry of the density field not only statistically, but also locally. Hence the critical points relative positions within the tomographic reconstruction could be used as standard rulers for dark energy by WEAVE-QSO and similar surveys.