Publications of Judith Biernaux
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See detailCosmological Time, Entropy and Infinity
Hauret, Clémentine ULiege; Magain, Pierre ULiege; Biernaux, Judith ULiege

in Entropy (2017), 19(7),

Time is a parameter playing a central role in our most fundamental modelling of natural laws. Relativity theory shows that the comparison of times measured by different clocks depends on their relative ... [more ▼]

Time is a parameter playing a central role in our most fundamental modelling of natural laws. Relativity theory shows that the comparison of times measured by different clocks depends on their relative motion and on the strength of the gravitational field in which they are embedded. In standard cosmology, the time parameter is the one measured by fundamental clocks (i.e., clocks at rest with respect to the expanding space). This proper time is assumed to flow at a constant rate throughout the whole history of the universe. We make the alternative hypothesis that the rate at which the cosmological time flows depends on the dynamical state of the universe. In thermodynamics, the arrow of time is strongly related to the second law, which states that the entropy of an isolated system will always increase with time or, at best, stay constant. Hence, we assume that the time measured by fundamental clocks is proportional to the entropy of the region of the universe that is causally connected to them. Under that simple assumption, we find it possible to build toy cosmological models that present an acceleration of their expansion without any need for dark energy while being spatially closed and finite, avoiding the need to deal with infinite values. [less ▲]

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See detailThe Bright and Dark Sides of elliptical galaxies
Biernaux, Judith ULiege

Poster (2017, January 29)

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See detailHow should we study the light distribution of strong lensing galaxies ?
Biernaux, Judith ULiege

Poster (2016, July)

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See detailAnalysis of luminosity distributions and shape parameters of strong gravitational lensing elliptical galaxies
Biernaux, Judith ULiege; Magain, Pierre ULiege; Sluse, Dominique ULiege et al

in Astronomy and Astrophysics (2016), 585

Context. The luminosity profiles of galaxies acting as strong gravitational lenses can be tricky to study. Indeed, strong gravitational lensing images display several lensed components, both point-like ... [more ▼]

Context. The luminosity profiles of galaxies acting as strong gravitational lenses can be tricky to study. Indeed, strong gravitational lensing images display several lensed components, both point-like and diffuse, around the lensing galaxy. Those objects restrain the study of the galaxy luminosity to its inner parts. Therefore, the usual fitting methods perform rather badly on such images. Previous studies of strong lenses luminosity profiles using such codes and various PSF-determining methods have resulted in somewhat discrepant results. Aims. The present work aims at investigating the causes of those discrepancies, as well as at designing more robust techniques to study the morphology of early-type lensing galaxies, with the ability to subtract lensed signal from their luminosity profiles. Methods. Each shape parameter, namely, the position angle, ellipticity and half-light radius of the galaxy, are determined as independently from each other as possible. The half-light radius measurement method is based on the computation of isophotes. Its robustness regarding various specific aspects of gravitational lensing image processing is analysed and tested versus that of a widely used fitting code, GALFIT. Those techniques are then applied on a sample of systems from the CASTLES database. Results. Simulations show that, when restricted to small, inner parts of the lensing galaxy, the technique presented here is more robust than GALFIT. It gives unbiased results, while GALFIT leads to an overestimation of the half-light radius that can reach about 10%, depending, among others, on the SNR. It is therefore better-suited than GALFIT for gravitational lensing images. It is also able to study lensing galaxies that are not much larger than the PSF, as opposed to GALFIT. New values for the half-light radius of the objects in our sample are presented and compared to previous works. [less ▲]

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See detailGravitational lensing search for dark matter haloes (2)
Biernaux, Judith ULiege

Conference (2015, May 13)

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See detailEtude de la matière sombre par effet de mirage gravitationnel
Biernaux, Judith ULiege

Scientific conference (2015, May 11)

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See detailGravitational lensing search for dark matter halos
Biernaux, Judith ULiege

Conference (2014, November 19)

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See detailEtude de la matière sombre par effet de mirage gravitationnel
Biernaux, Judith ULiege

Master's dissertation (2014)

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