Search Publications
Model-independent reconstruction of UV luminosity function and reionization epoch
Hazra, Dhiraj Kumar; Adak, Debabrata; Mitra, Sourav +1 more
We conduct a first comprehensive study of the Luminosity Function (LF) using a non-parametric approach. We use Gaussian Process to fit available luminosity data between redshifts z ∼ 2-8. Our free-form LF in the non-parametric approach rules out the conventional Schechter function model to describe the abundance-magnitude relation at redshifts z=3…
Lensing substructure quantification in RXJ1131-1231: a 2 keV lower bound on dark matter thermal relic mass
Amara, Adam; Refregier, Alexandre; Birrer, Simon
We study the substructure content of the strong gravitational lens RXJ1131-1231 through a forward modelling approach that relies on generating an extensive suite of realistic simulations. We use a semi-analytic merger tree prescription that allows us to stochastically generate substructure populations whose properties depend on the dark matter par…
CLASH-VLT: constraints on f(R) gravity models with galaxy clusters using lensing and kinematic analyses
Grillo, C.; Balestra, I.; Rosati, P. +10 more
We perform a maximum likelihood kinematic analysis of the two dynamically relaxed galaxy clusters MACS J1206.2-0847 at z=0.44 and RXC J2248.7-4431 at z=0.35 to determine the total mass profile in modified gravity models, using a modified version of the MAMPOSSt code of Mamon, Biviano and Bou&apose. Our work is based on the kinematic and lensin…
The mass-sheet degeneracy and time-delay cosmography: analysis of the strong lens RXJ1131-1231
Amara, Adam; Refregier, Alexandre; Birrer, Simon
We present extended modelling of the strong lens system RXJ1131-1231 with archival data in two HST bands in combination with existing line-of-sight contribution and velocity dispersion estimates. Our focus is on source size and its influence on time-delay cosmography. We therefore examine the impact of mass-sheet degeneracy and especially the dege…
Accurate shear measurement with faint sources
Zhang, Jun; Luo, Wentao; Foucaud, Sebastien
For cosmic shear to become an accurate cosmological probe, systematic errors in the shear measurement method must be unambiguously identified and corrected for. Previous work of this series has demonstrated that cosmic shears can be measured accurately in Fourier space in the presence of background noise and finite pixel size, without assumptions …
Constraints on cosmological models from strong gravitational lensing systems
Cao, Shuo; Biesiada, Marek; Zhu, Zong-Hong +2 more
Strong lensing has developed into an important astrophysical tool for probing both cosmology and galaxies (their structure, formation, and evolution). Using the gravitational lensing theory and cluster mass distribution model, we try to collect a relatively complete observational data concerning the Hubble constant independent ratio between two an…
The rates and time-delay distribution of multiply imaged supernovae behind lensing clusters
Richard, Johan; Hjorth, Jens; Li, Xue
Time delays of gravitationally lensed sources can be used to constrain the mass model of a deflector and determine cosmological parameters. We here present an analysis of the time-delay distribution of multiply imaged sources behind 17 strong lensing galaxy clusters with well-calibrated mass models. We find that for time delays less than 1000 days…
Exploring the properties of dark energy using type-Ia supernovae and other datasets
Starobinsky, Alexei A.; Alam, Ujjaini; Sahni, Varun
We reconstruct dark energy properties from two complementary supernova datasets—the newly released Gold + HST sample and SNLS. The results obtained are consistent with the standard ΛCDM model within 2σ error bars, although the Gold + HST data favour evolving dark energy slightly more than SNLS. Using complementary data from baryon acoustic oscilla…