Testing the Standard Cosmological Model

This thesis exploits the wealth of information contained in the existing cosmological surveys, and demonstrates how the use of tools such as two-point statistics permit the extraction of such information. In particular, the wide field imaging survey – the Sloan Digital Sky Survey (SDSS) in conjunction with Luminous Red Galaxy (LRG) spectroscopic surveys carried out by the Two-degree-Field (2dF) and AAOmega instruments on the Anglo-Australian telescope (AAT) are utilised here. This also includes the observations of the Cosmic Microwave Background (CMB) radiation from the Wilkinson Microwave Anisotropy Probe (WMAP) experiment. Combining the imaging and spectroscopic surveys, we extract three photometric LRG samples at redshift 0.35, 0.55 and 0.7 which cover 7600 deg2 of the sky, probing a total cosmic volume of 5.5 h^−3 Gpc^3. We find very little clustering evolution in these massive early-type galaxies out to z~0.8 or nearly half the age of the Universe. The shape of the large-scale correlation functions is consistent with a simple ‘high-peaks’ bias and linear theory framework of the standard CDM model. The new z=0.7 LRG sample is then used in the CMB-LSS cross-correlation analysis to look for the the Integrated Sachs-Wolfe (ISW) effect as a dynamical evidence for the accelerated expansion of the Universe. The measured zero CMB-LRG correlation is inconsistent with the CDM model expectation at 2.2sigma significance level. Furthermore, our rotation tests show that the previous detections of the ISW effect may not be as significant as previously claimed. We make independent estimates of the WMAP CMB temperature power spectra and show explicitly how sensitive they are to the instrumental beams. We propose an alternative method for determining the beam profiles by stacking radio point sources and demonstrate its robustness via Monte Carlo simulations plus realistic point source detection algorithm. Using this technique, we find significantly wider W-band beam profiles than the WMAP Jupiter beam analysis. We also find a tentative evidence for a non-linearity in the WMAP radio source fluxes when compared with the ground-based measurements. Finally, we investigate if the recently claimed timing offset in the WMAP time-ordered data can explain the observed wider than expected beam profile

Weak lensing analysis of CODEX clusters using dark energy camera legacy survey : mass-richness relation

We present the weak-lensing analysis of 279 CODEX clusters using imaging data from 4200 deg(2) of the DECam Legacy Survey (DECaLS) Data Release 3. The cluster sample results from a joint selection in X-ray, optical richness in the range 20 proportional to M-0 (lambda/40)(F lambda). By measuring the CODEX cluster sample as an individual cluster, we obtain the best-fitting values, M-0 = 3.24(-0.27)(+0.29) x 10(14)M(circle dot), and F-lambda = 1.00(-0.22)(+0.22) for the richness scaling index, consistent with a power-law relation. Moreover, we separate the cluster sample into three richness groups; lambda = 20-30, 30-50, and 50-110, and measure the stacked excess surface mass density profile in each group. The results show that both methods are consistent. In addition, we find an excellent agreement between our weak lensing based scaling relation and the relation obtained with dynamical masses estimated from cluster member velocity dispersions measured by the SDSS-IV/SPIDERS team. This suggests that the cluster dynamical equilibrium assumption involved in the dynamical mass estimates is statistically robust for a large sample of clusters.Peer reviewe

Potential of Core-Collapse Supernova Neutrino Detection at JUNO

JUNO is an underground neutrino observatory under construction in Jiangmen, China. It uses 20kton liquid scintillator as target, which enables it to detect supernova burst neutrinos of a large statistics for the next galactic core-collapse supernova (CCSN) and also pre-supernova neutrinos from the nearby CCSN progenitors. All flavors of supernova burst neutrinos can be detected by JUNO via several interaction channels, including inverse beta decay, elastic scattering on electron and proton, interactions on C12 nuclei, etc. This retains the possibility for JUNO to reconstruct the energy spectra of supernova burst neutrinos of all flavors. The real time monitoring systems based on FPGA and DAQ are under development in JUNO, which allow prompt alert and trigger-less data acquisition of CCSN events. The alert performances of both monitoring systems have been thoroughly studied using simulations. Moreover, once a CCSN is tagged, the system can give fast characterizations, such as directionality and light curve

Real-time Monitoring for the Next Core-Collapse Supernova in JUNO

Core-collapse supernova (CCSN) is one of the most energetic astrophysical events in the Universe. The early and prompt detection of neutrinos before (pre-SN) and during the SN burst is a unique opportunity to realize the multi-messenger observation of the CCSN events. In this work, we describe the monitoring concept and present the sensitivity of the system to the pre-SN and SN neutrinos at the Jiangmen Underground Neutrino Observatory (JUNO), which is a 20 kton liquid scintillator detector under construction in South China. The real-time monitoring system is designed with both the prompt monitors on the electronic board and online monitors at the data acquisition stage, in order to ensure both the alert speed and alert coverage of progenitor stars. By assuming a false alert rate of 1 per year, this monitoring system can be sensitive to the pre-SN neutrinos up to the distance of about 1.6 (0.9) kpc and SN neutrinos up to about 370 (360) kpc for a progenitor mass of 30$M_{\odot}$ for the case of normal (inverted) mass ordering. The pointing ability of the CCSN is evaluated by using the accumulated event anisotropy of the inverse beta decay interactions from pre-SN or SN neutrinos, which, along with the early alert, can play important roles for the followup multi-messenger observations of the next Galactic or nearby extragalactic CCSN.Comment: 24 pages, 9 figure

Detection of the Diffuse Supernova Neutrino Background with JUNO

As an underground multi-purpose neutrino detector with 20 kton liquid scintillator, Jiangmen Underground Neutrino Observatory (JUNO) is competitive with and complementary to the water-Cherenkov detectors on the search for the diffuse supernova neutrino background (DSNB). Typical supernova models predict 2-4 events per year within the optimal observation window in the JUNO detector. The dominant background is from the neutral-current (NC) interaction of atmospheric neutrinos with 12C nuclei, which surpasses the DSNB by more than one order of magnitude. We evaluated the systematic uncertainty of NC background from the spread of a variety of data-driven models and further developed a method to determine NC background within 15\% with {\it{in}} {\it{situ}} measurements after ten years of running. Besides, the NC-like backgrounds can be effectively suppressed by the intrinsic pulse-shape discrimination (PSD) capabilities of liquid scintillators. In this talk, I will present in detail the improvements on NC background uncertainty evaluation, PSD discriminator development, and finally, the potential of DSNB sensitivity in JUNO

Void profile from Planck lensing potential map

International audienceWe use the lensing potential map from Planck CMB lensing reconstruction analysis and the “Public Cosmic Void Catalog” to measure the stacked void lensing potential. We have made an attempt to fit the HSW void profile parameters from the stacked lensing potential. In this profile, four parameters are needed to describe the shape of voids with different characteristic radii R ( )V( ). However, we have found that after reducing the background noise by subtracting the average background, there is a residue lensing power left in the data. The inclusion of the environment shifting parameter, ${\gamma }_{V}$, is necessary to get a better fit to the data with the residue lensing power. We divide the voids into two redshift bins: cmass1 ($0.45\lt z\lt 0.5$) and cmass2 ($0.5\lt z\lt 0.6$). Our best-fit parameters are $\alpha =1.989\pm 0.149$, $\beta =12.61\pm 0.56$, ${\delta }_{c}=-0.697\pm 0.025$, ${R}_{S}/{R}_{V}=1.039\pm 0.030$, ${\gamma }_{v}=(-7.034\pm 0.150)\times {10}^{-2}$ for the cmass1 sample with 123 voids and $\alpha =1.956\pm 0.165$, $\beta \,=12.91\pm 0.60$, ${\delta }_{c}=-0.673\pm 0.027$, ${R}_{S}/{R}_{V}=1.115\pm 0.032$, ${\gamma }_{v}=(-4.512\pm 0.114)\times {10}^{-2}$ for the cmass2 sample with 393 voids at 68% C.L. The addition of the environment shifting parameter is consistent with the conjecture that the Sloan Digital Sky Survey voids reside in an underdense region