Sloan Digital Sky Survey | EPFL Graph Search

The Sloan Digital Sky Survey or SDSS is a major multi-spectral imaging and spectroscopic redshift survey using a dedicated 2.5-m wide-angle optical telescope at Apache Point Observatory in New Mexico, United States. The project began in 2000 and was named after the Alfred P. Sloan Foundation, which contributed significant funding. A consortium of the University of Washington and Princeton University was established to conduct a redshift survey. The Astrophysical Research Consortium (ARC) was established in 1984 with the additional participation of New Mexico State University and Washington State University to manage activities at Apache Point. In 1991, the Sloan Foundation granted the ARC funding for survey efforts and the construction of equipment to carry out the work. Background At the time of its design, the SDSS was a pioneering combination of novel instrumentation as well as data reduction and storage techniques that drove major advances in astronomical observations,

Cosmology with Large Scale Structures using Massive Spectroscopic Surveys

Amélie Tamone

Spectroscopic surveys aim to map large fractions of the Universe to study the Large Scale Structures (LSS). LSS evolution traces the distribution of matter as a result of the tension between the expansion of the Universe and the gravitational forces, which means that LSS can be used to test cosmological and gravity model, in particular the standard model of cosmology (

\Lambda

CDM) with General Relativity (GR). One usual way to study those LSS is to quantify the clustering of the galaxies with the 2-point correlation function (2PCF). The Baryon Acoustic Oscillations (BAO) signature is characterised as a peak in the 2PCF, whose position is related to the Hubble parameter. Moreover, Redshift Space Distortions (RSD) are imprinted in the 2PCF and are used to measure the growth rate of structure of the Universe. In this thesis I measured the growth rate of structure of the emission line galaxy (ELG) sample of the extended Baryon Oscillation Spectroscopic Survey (eBOSS) from RSD in configuration space. I was able along with the Sloan Digital Sky Survey (SDSS) collaboration to participate to the final cosmological implication of the past 20 years of SDSS. By a combination of probes, the current cosmological parameters were then constrained with a high precision, outpassing the expected constraints for Stage-III dark energy experiment.Moreover I performed a BAO analysis with voids, tracing the underdensities in the quasars (QSO) sample of eBOSS. While the method was shown to bring great improvement on other tracers, it reveals itself more difficult to deal with quasars due to their low density. I was nevertheless able to detect a BAO signal and to provide forecast for a QSO sample from a DESI-like (Dark Energy Spectroscopic Instrument) experiment.

EPFL2022

CODEX clusters: Survey, catalog, and cosmology of the X-ray luminosity function

Johan Comparat, Ghazaleh Erfanianfar, Jean-Paul Richard Kneib

Context. Large area catalogs of galaxy clusters constructed from ROSAT All-Sky Survey provide the basis for our knowledge of the population of clusters thanks to long-term multiwavelength efforts to follow up observations of these clusters.Aims. The advent of large area photometric surveys superseding previous, in-depth all-sky data allows us to revisit the construction of X-ray cluster catalogs, extending the study to lower cluster masses and higher redshifts and providing modeling of the selection function.Methods. We performed a wavelet detection of X-ray sources and made extensive simulations of the detection of clusters in the RASS data. We assigned an optical richness to each of the 24 788 detected X-ray sources in the 10 382 square degrees of the Baryon Oscillation Spectroscopic Survey area using red sequence cluster finder redMaPPer version 5.2 run on Sloan Digital Sky Survey photometry. We named this survey COnstrain Dark Energy with X-ray (CODEX) clusters.Results. We show that there is no obvious separation of sources on galaxy clusters and active galactic nuclei (AGN) based on the distribution of systems on their richness. This is a combination of an increasing number of galaxy groups and their selection via the identification of X-ray sources either by chance or by groups hosting an AGN. To clean the sample, we use a cut on the optical richness at the level corresponding to the 10% completeness of the survey and include it in the modeling of the cluster selection function. We present the X-ray catalog extending to a redshift of 0.6.Conclusions. The CODEX suvey is the first large area X-ray selected catalog of northern clusters reaching fluxes of 10(-13) ergs s(-1) cm(-2). We provide modeling of the sample selection and discuss the redshift evolution of the high end of the X-ray luminosity function (XLF). Our results on z< 0.3 XLF agree with previous studies, while we provide new constraints on the 0.3< z< 0.6 XLF. We find a lack of strong redshift evolution of the XLF, provide exact modeling of the effect of low number statistics and AGN contamination, and present the resulting constraints on the flat CDM.

EDP SCIENCES S A2020