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Q. Petit

Publications and source records attributed to Q. Petit.

2 recordsLinked to original sources

Gaia GraL X.: The GraL catalogue of gravitationally lensed quasars Matched with \textit{Gaia} data, redshifts, and time delays

Determining the Hubble constant tension requires alternative strategies, and multiply imaged quasars, with their intermediate redshifts, can potentially be used in this regard. We provide a currently complete catalogue of spectroscopically confirmed lensed quasars with ESA/{\it Gaia} astrometry and photometry, as well as redshifts and time delays when available. In addition to the improved astrometry, the catalogue increases the number of lensed quasars by a factor of 1.5 (now 364, of which 277 are doubles and 87 are quads or triples) and significantly increases the number of lensing galaxies detected (now 218), which represents a major step forward. Redshifts are provided for 347 quasars and 188 deflectors. A completely new table of time delays, required for estimates of $H_0$, is presented, with 195 time delays from 73 systems. {\it Gaia} absolute astrometry is sub-milliarcsecond and covers the entire sky. Future {\it Gaia} data releases will provide long-term photometry, which should provide many more time delays. The catalogues as presented here enable machine-learning techniques to be trained and tested and subsequently applied to the {\it Gaia} data releases. Finally, we derive simple but homogeneous models of the 18 quadruply imaged quasars for which images of all four components are presented in {\it Gaia} DR3.}

astro-ph.GA

Shape, alignment, and mass distribution of baryonic and dark-matter halos in one EAGLE simulation

Accurate knowledge of the morphology of halos and its evolution are key constraints on the galaxy formation model as well as a determinant parameter of the strong-lensing phenomenon. Using the cosmological hydrodynamic simulation, the Evolution and Assembly of GaLaxies and their Environments (EAGLE), we aim to provide a comprehensive analysis of the evolution of the morphology of galaxy halos and of their mass distributions with a focus on the snapshot at redshift $z=0.5$. We developed an iterative strategy involving a principal component analysis (PCA) to investigate the properties of the EAGLE halos and the differences in alignment between the various components. The mass distributions of the dark-matter (DM), gas, and star halos are characterised by a half-mass radius, a concentration parameter and (projected) axis ratios. We present statistics of the shape parameters of 336\,540 halos from the EAGLE RefL0025N0376 simulation and describe their evolution from redshift $z=15$ to $z=0$. We measured the three-dimensional and two-dimensional projected shape parameters for the DM, the gas, and the star components as well as for all particles. At $z=0.5$, the minor axis of gas aligns with the minor axis of DM for massive halos ($M>10^{12}$ M$_\odot$), but this alignment is poorer for less massive halos. The DM halos axis ratios $b/a$ and $c/a$ have median values of $0.82 \pm 0.11$ and $0.64 \pm 0.12$, respectively. The sphericity of gas in halos w/ and w/o stars appears to be negatively correlated to the total mass, while the sphericity of DM is insensitive to it. The measured projected axis ratios, $b_p/a_p$, of star halos at $z=0.5$ have a median value of $0.80 \pm 0.07$, which is in good agreement with ground-based and space-based measurements within 1 $σ$. For DM halos, we measure a value of $0.85 \pm 0.06$.

astro-ph.GA