Redshift space three-point correlation function of IGM at $z<0.48$

TLDR: 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.

Abstract: The Ly$\alpha$ forest decomposed into Voigt profile components (or "clouds") allow us to study clustering properties of the intergalactic medium and its dependence on various physical quantities. Here, we report the first detections of longitudinal three-point ($\zeta$) and reduced three-point (Q) correlations of low-$z$ (i.e $z $40 km/s) and low-$b$ absorbers. About 84% of the triplets contributing to $\zeta$ have nearby galaxies within a velocity separation of 500 km/s and a median impact parameter of 405 pkpc. The measured impact parameters are consistent with appreciable number of triplets not originating from individual galaxies but tracing the underlying galaxy distribution. Frequency of occurrence of high-$b$ absorbers in triplets ($\sim$88%) is a factor $\sim3$ higher than that found among the full sample ($\sim$32%). Using four different cosmological simulations, we quantify the effect of peculiar velocities, feedback effects and show that most of the observed trends can be broadly reproduced. However, $\zeta$ at small scales ($r_\parallel 10^{14}$ cm$^{-2}$ self-consistently or to the widespread of signal-to-noise ratio in the observed data.