Publications by Andrei Variu | EPFL Graph Search

Suppressing the sample variance of DESI-like galaxy clustering with fast simulations

Ongoing and upcoming galaxy redshift surveys, such as the Dark Energy Spectroscopic Instrument (DESI) survey, will observe vast regions of sky and a wide range of redshifts. In order to model the observations and address various systematic uncertainties, N ...

IOP Publishing Ltd2025

Validation of the Scientific Program for the Dark Energy Spectroscopic Instrument

Eduardo Sanchez, Zhifeng Ding, Sun Hee Kim, Hua Zhang, Stewart Cole, Jiangyan Yang, Jean-Paul Richard Kneib, Anand Stéphane Raichoor, Andrei Variu, Ting Tan, Daniel Felipe Forero Sanchez, Cheng Zhao, Arjun Dey, David Schlegel, Zheng Zheng, Xin Chen

The Dark Energy Spectroscopic Instrument (DESI) was designed to conduct a survey covering 14,000 deg(2) over 5 yr to constrain the cosmic expansion history through precise measurements of baryon acoustic oscillations (BAO). The scientific program for DESI ...

Iop Publishing Ltd2024

Probing the nature of Dark Energy through the study of large scale structures using spectroscopic surveys and their simulations

Andrei Variu

Measurements of large-scale structure (LSS), as performed on the largest 3D map of over two million extragalactic sources from the Sloan Digital Sky Survey, together with measurements of the cosmic microwave background (CMB) anisotropies, are in complete a ...

EPFL2023

Cosmic void exclusion models and their impact on the distance scale measurements from large-scale structure

Jean-Paul Richard Kneib, Amélie Tamone, Andrei Variu, Daniel Felipe Forero Sanchez, Cheng Zhao

Baryonic Acoustic Oscillations (BAOs) studies based on the clustering of voids and matter tracers provide important constraints on cosmological parameters related to the expansion of the Universe. However, modelling the void exclusion effect is an importan ...

OXFORD UNIV PRESS2023

DESI mock challenge: constructing DESI galaxy catalogues based on FastPM simulations

Jean-Paul Richard Kneib, Andrei Variu, Cheng Zhao

Together with larger spectroscopic surveys such as the Dark Energy Spectroscopic Instrument (DESI), the precision of large-scale structure studies and thus the constraints on the cosmological parameters are rapidly improving. Therefore, one must build real ...

Oxford Univ Press2023

Void BAO measurements on quasars from eBOSS

Jean-Paul Richard Kneib, Amélie Tamone, Andrei Variu, Daniel Felipe Forero Sanchez, Cheng Zhao

We present the clustering of voids based on the quasar (QSO) sample of the extended Baryon Oscillation Spectroscopic Survey Data Release 16 in configuration space. We define voids as overlapping empty circumspheres computed by Delaunay tetrahedra spanned b ...

Oxford Univ Press2023

First detection of the BAO signal from early DESI data

Anand Stéphane Raichoor, Andrei Variu, Cheng Zhao, David Schlegel

We present the first detection of the baryon acoustic oscillations (BAOs) signal obtained using unblinded data collected during the initial 2 months of operations of the Stage-IV ground-based Dark Energy Spectroscopic Instrument (DESI). From a selected sam ...

Oxford Univ Press2023

Cosmic void baryon acoustic oscillation measurement: evaluation of sensitivity to selection effects

Jean-Paul Richard Kneib, Amélie Tamone, Andrei Variu, Daniel Felipe Forero Sanchez, Cheng Zhao

Cosmic voids defined as a subset of Delaunay triangulation (DT) circumspheres have been used to measure the baryon acoustic oscillations (BAO) scale; providing tighter constraints on cosmological parameters when combined with matter tracers. These voids ar ...

OXFORD UNIV PRESS2022

The DESI N-body Simulation Project - II. Suppressing sample variance with fast simulations

Yu Yu, Andrei Variu, Cheng Zhao, Hanyu Zhang

Dark Energy Spectroscopic Instrument (DESI) will construct a large and precise three-dimensional map of our Universe. The survey effective volume reaches similar to 20 h(-3) Gpc(3). It is a great challenge to prepare high-resolution simulations with a much ...

OXFORD UNIV PRESS2022

The completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey: cosmological implications from multitracer BAO analysis with galaxies and voids

Jean-Paul Richard Kneib, Huanyuan Shan, Amélie Tamone, Andrei Variu, Jiaxi Yu, Daniel Felipe Forero Sanchez, Cheng Zhao

We construct cosmic void catalogues with the DIVE void finder upon SDSS BOSS DR12 and eBOSS DR16 galaxy samples with BAO reconstruction, and perform a joint BAO analysis using different types of galaxies and the corresponding voids. The BAO peak is evident ...

OXFORD UNIV PRESS2022

An atlas of MUSE observations towards twelve massive lensing clusters

Jean-Paul Richard Kneib, Amélie Tamone, Andrei Variu, Benjamin Yvan Alexandre Clement

Context. Spectroscopic surveys of massive galaxy clusters reveal the properties of faint background galaxies thanks to the magnification provided by strong gravitational lensing.Aims. We present a systematic analysis of integral-field-spectroscopy observat ...

EDP SCIENCES S A2021

Completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey: Cosmological implications from two decades of spectroscopic surveys at the Apache Point Observatory

Johan Comparat, Jean-Paul Richard Kneib, Amélie Tamone, Anand Stéphane Raichoor, Andrei Variu, Cheng Zhao, Yuting Wang, Zheng Zheng

We present the cosmological implications from final measurements of clustering using galaxies, quasars, and Ly alpha forests from the completed Sloan Digital Sky Survey (SDSS) lineage of experiments in large-scale structure. These experiments, composed of ...

American Physical Society2021

Improving baryon acoustic oscillation measurement with the combination of cosmic voids and galaxies

Yu Liang, Andrei Variu, Cheng Zhao

We develop a methodology to optimize the measurement of baryon acoustic oscillation (BAO) from a given galaxy sample. In our previous work, we demonstrated that one can measure BAO from tracers in underdense regions (voids). In this study, we combine the o ...

OXFORD UNIV PRESS2020