Soumak Maitra

TL;DR: In this paper, two-and three-point correlation functions of Ly$\alpha$ forest were analyzed using X-Shooter spectra of three background quasar triplets probing transverse separations of 0.5-1.6 pMpc.

Abstract: Ly$\alpha$ forest absorption spectra decomposed into multiple Voigt profile components (clouds) allow us to study clustering of intergalactic medium (IGM) as a function of HI column density ($N_{\rm HI}$). Here, we explore the transverse three-point correlation ($\zeta$) of these Ly$\alpha$ clouds using mock triplet spectra obtained from hydrodynamical simulations at $z \sim 2$ on scales of 1-5 $h^{-1}$cMpc. We find $\zeta$ to depend strongly on $N_{\rm HI}$ and scale and weakly on angle ($\theta$) of the triplet configuration. We show that the "hierarchical ansatz" is applicable for scales $\ge~ 3h^{-1}$cMpc, and obtain a median reduced three-point correlation (Q) in the range 0.2-0.7. We show, $\zeta$ is influenced strongly by the thermal and ionization state of the gas. As found in the case of galaxies, the influence of physical parameters on Q is weaker compared to that of $\zeta$. We show difference in $\zeta$ and Q between different simulations are minimized if we use appropriate $N_{\rm HI}$ cut-offs corresponding to a given baryon over-density ($\Delta$) using the measured $N_{\rm HI}~vs~\Delta$ relationship obtained from individual simulations. Additionally, we see the effect of pressure broadening on $\zeta$ in a model with artificially boosted heating rates. However, for models with realistic thermal and ionization histories the effect of pressure broadening on $\zeta$ is weak and sub-dominant compared to other local effects. We find strong redshift evolution shown by $\zeta$, mainly originating from the redshift evolution of thermal and ionization state of the IGM. We discuss the observational requirements for the detection of three-point correlation, specifically, in small intervals of configuration parameters and redshift.

TL;DR: The QUBRICS (QUasars as BRIght beacons for Cosmology in the Southern hemisphere) survey aims at constructing a sample of the brightest quasars with $z = 0.02 as discussed by the authors .

TL;DR: In this paper, the authors reported the first detections of longitudinal three-point and reduced threepoint correlations of low-$z$ (i.e. $z $40 km/s) and low-$b$ absorbers.

TL;DR: In this paper, the authors present redshift space two-point, three-point and reduced threepoint (Q) correlation of Ly$\alpha$ absorbers (i.e. Voigt profile components having HI column density 10−13.5−1.5 ) over three redshift bins spanning $1.7-2.3