Publications de Jiaxi Yu | EPFL Graph Search

Optimal reconstruction of baryon acoustic oscillations for DESI 2024

Baryon acoustic oscillations (BAO) provide a robust standard ruler to measure the expansion history of the Universe through galaxy clustering. Density-field reconstruction is now a widely adopted procedure for increasing the precision and accuracy of the B ...

2025

DESI 2024 III: baryon acoustic oscillations from galaxies and quasars

Jiaxi Yu, Daniel Felipe Forero Sanchez

We present the DESI 2024 galaxy and quasar baryon acoustic oscillations (BAO) measurements using over 5.7 million unique galaxy and quasar redshifts in the range 0.1 < z < 2.1. Divided by tracer type, we utilize 300,017 galaxies from the magnitude-limited ...

2025

DESI 2024 IV: Baryon Acoustic Oscillations from the Lyman alpha forest

Jiaxi Yu, Daniel Felipe Forero Sanchez

We present the measurement of Baryon Acoustic Oscillations (BAO) from the Lyman- a (Lya) forest of high-redshift quasars with the first-year dataset of the Dark Energy Spectroscopic Instrument (DESI). Our analysis uses over 420 000 Lya forest spectra and t ...

IOP Publishing Ltd2025

Fiducial-cosmology-dependent systematics for the DESI 2024 BAO analysis

Jiaxi Yu

When measuring the Baryon Acoustic Oscillations (BAO) scale from galaxy surveys, one typically assumes a fiducial cosmology when converting redshift measurements into comoving distances and also when defining input parameters for the reconstruction algorit ...

IOP Publishing Ltd2025

Analytical and EZmock covariance validation for the DESI 2024 results

Jiaxi Yu, Daniel Felipe Forero Sanchez

The estimation of uncertainties in cosmological parameters is an important challenge in Large-Scale-Structure (LSS) analyses. For standard analyses such as Baryon Acoustic Oscillations (BAO) and Full-Shape two approaches are usually considered. First: anal ...

2025

Impact and mitigation of spectroscopic systematics on DESI DR1 clustering measurements

Jiaxi Yu

The large scale structure catalogs within DESI Data Release 1 (DR1) use nearly 6 million galaxies and quasars as tracers of the large-scale structure of the universe to measure the expansion history with baryon acoustic oscillations and the growth of struc ...

IOP Publishing Ltd2025

Desi 2024 Vi: Cosmological Constraints From the Measurements of Baryon Acoustic Oscillations

Jiaxi Yu, Daniel Felipe Forero Sanchez

We present cosmological results from the measurement of baryon acoustic oscillations (BAO) in galaxy, quasar and Lyman-alpha forest tracers from the first year of observations from the Dark Energy Spectroscopic Instrument (DESI), to be released in the DESI ...

IOP Publishing Ltd2025

Hod-dependent Systematics in Emission Line Galaxies for the Desi 2024 Bao Analysis

Jiaxi Yu

The Dark Energy Spectroscopic Instrument (DESI) will provide precise measurements of Baryon Acoustic Oscillations (BAO) to constrain the expansion history of the Universe and set stringent constraints on dark energy. Therefore, precise control of the globa ...

IOP Publishing Ltd2025

Mitigating imaging systematics for DESI 2024 emission Line Galaxies and beyond

Jiaxi Yu

Emission Line Galaxies (ELGs) are one of the main tracers that the Dark Energy Spectroscopic Instrument (DESI) uses to probe the universe. However, they are afflicted by strong spurious correlations between target density and observing conditions known as ...

IOP Publishing2025

Semi-analytical covariance matrices for two-point correlation function for DESI 2024 data

Jiaxi Yu, Daniel Felipe Forero Sanchez

We present an optimized way of producing the fast semi-analytical covariance matrices for the Legendre moments of the two-point correlation function, taking into account survey geometry and mimicking the non-Gaussian effects. We validate the approach on si ...

IOP Publishing Ltd2025

ELG spectroscopic systematics analysis of the DESI Data Release 1

Jean-Paul Richard Kneib, Jiaxi Yu, Daniel Felipe Forero Sanchez

Dark Energy Spectroscopic Instrument (DESI) uses more than 2.4 million Emission Line Galaxies (ELGs) for 3D large-scale structure (LSS) analyses in its Data Release 1 (DR1). Such large statistics enable thorough research on systematic uncertainties. In thi ...

IOP Publishing Ltd2025

The construction of large-scale structure catalogs for the Dark Energy Spectroscopic Instrument

Jiaxi Yu

We present the technical details on how large-scale structure (LSS) catalogs are constructed from redshifts measured from spectra observed by the Dark Energy Spectroscopic Instrument (DESI). The LSS catalogs provide the information needed to determine the ...

IOP Publishing Ltd2025

HOD-dependent systematics for luminous red galaxies in the DESI 2024 BAO analysis

Jiaxi Yu

In this paper, we present the estimation of systematics related to the halo occupation distribution (HOD) modeling in the baryon acoustic oscillations (BAO) distance measurement of the Dark Energy Spectroscopic Instrument (DESI) 2024 analysis. This paper f ...

IOP Publishing Ltd2025

The DESI One-Percent Survey: exploring a generalized SHAM for multiple tracers with the UNIT simulation

Jean-Paul Richard Kneib, Jiaxi Yu, Cheng Zhao

We perform SubHalo Abundance Matching (SHAM) studies on UNIT simulations with {sigma, V-ceil, v(smear)}-SHAM and {sigma, V-ceil, f(sat)}-SHAM. They are designed to reproduce the clustering on 5-30 h(-1) Mpc of luminous red galaxies (LRGs), emission-line ga ...

Oxford Univ Press2024

Baryon acoustic oscillation theory and modelling systematics for the DESI 2024 results

Jiaxi Yu, Daniel Felipe Forero Sanchez

This paper provides a comprehensive overview of how fitting of baryon acoustic oscillations (BAO) is carried out within the upcoming Dark Energy Spectroscopic Instrument’s (DESI) 2024 results using its DR1 data set, and the associated systematic error budg ...

2024

Overview of the Fiber System for the Dark Energy Spectroscopic Instrument

Jiaxi Yu

The Dark Energy Spectroscopic Instrument (DESI) is a revolutionary instrument designed for precise measurements of cosmic distances and the investigation of dark energy. DESI utilizes 5000 optical fibers to simultaneously measure the spectra of distant obj ...

2024

A Brief History of Cosmology with Galaxy-Halo Relation and Systematics in Redshift Surveys

Jiaxi Yu

This dissertation traces the evolution of cosmology from its foundational theories to the forefront of modern observational studies, with a particular focus on the role of large-scale structure (LSS) probes. It begins with the establishment of General Rela ...

EPFL2024

The DESI one-per cent survey: exploring the halo occupation distribution of luminous red galaxies and quasi-stellar objects with ABACUSSUMMIT

Jiaxi Yu, Hanyu Zhang, Zheng Zheng

We present the first comprehensive halo occupation distribution (HOD) analysis of the Dark Energy Spectroscopic Instrument (DESI) One-Percent Survey luminous red galaxy (LRG) and Quasi Stellar Object (QSO) samples. We constrain the HOD of each sample and t ...

2024

The DESI Survey Validation: Results from Visual Inspection of Bright Galaxies, Luminous Red Galaxies, and Emission-line Galaxies

Stewart Cole, Yi Zhang, Anand Stéphane Raichoor, Jiaxi Yu, Arjun Dey

The Dark Energy Spectroscopic Instrument (DESI) Survey has obtained a set of spectroscopic measurements of galaxies to validate the final survey design and target selections. To assist in these tasks, we visually inspect DESI spectra of approximately 2500 ...

IOP Publishing Ltd2023

The DESI One-Percent Survey: Constructing Galaxy-Halo Connections for ELGs and LRGs Using Auto and Cross Correlations

Jiaxi Yu

In the current Dark Energy Spectroscopic Instrument (DESI) survey, emission line galaxies (ELGs) and luminous red galaxies (LRGs) are essential for mapping the dark matter distribution at < N(M)>. We measure the auto and cross correlation functions of ELGs ...

IOP Publishing Ltd2023