Euclid: Forecasts from the void-lensing cross-correlation

Abstract

The Euclid space telescope will survey a large dataset of cosmic voids traced by dense samples of galaxies. In this work we estimate its expected performance when exploiting angular photometric void clustering, galaxy weak lensing and their cross-correlation. To this aim, we implement a Fisher matrix approach tailored for voids from the Euclid photometric dataset and present the first forecasts on cosmological parameters that include the void-lensing correlation. We examine two different probe settings, pessimistic and optimistic, both for void clustering and galaxy lensing. We carry out forecast analyses in four model cosmologies, accounting for a varying total neutrino mass, M ν , and a dynamical dark energy (DE) equation of state, w(z), described by the popular Chevallier-Polarski-Linder parametrisation. We find that void clustering constraints on h and Ω b are competitive with galaxy lensing alone, while errors on n s decrease thanks to the orthogonality of the two probes in the 2D-projected parameter space. We also note that, as a whole, with respect to assuming the two probes as independent, the inclusion of the void-lensing crosscorrelation signal improves parameter constraints by 10 − 15%, and enhances the joint void clustering and galaxy lensing Figure of Merit (FoM) by 10% and 25%, in the pessimistic and optimistic scenarios, respectively. Finally, when further combining with the spectroscopic galaxy clustering, assumed as an independent probe, we find that, in the most competitive case, the FoM increases by a factor of 4 with respect to the combination of weak lensing and spectroscopic galaxy clustering taken as independent probes. The forecasts presented in this work show that photometric void-clustering and its cross-correlation with galaxy lensing deserve to be exploited in the data analysis of the Euclid galaxy survey and promise to improve its constraining power, especially on h, Ω b , the neutrino mass, and the DE evolution.

Euclid: Cosmological forecasts from the void size function

“…Cosmic voids from recent galaxy surveys have been used in a wide range of cosmological applications. They are sensitive to geometric effects, such as the Alcock-Paczyński effect (Alcock & Paczynski 1979;Sutter et al 2012Sutter et al , 2014bHamaus et al 2016;Mao et al 2017a) and baryonic acoustic oscillations (Kitaura et al 2016;Liang et al 2016;Chan & Hamaus 2021;Forero-Sánchez et al 2022;Khoraminezhad et al 2022), as well as redshift-space distortions (RSD, Paz et al 2013;Hamaus et al 2014aHamaus et al , 2015Cai et al 2016;Chuang et al 2017;Achitouv et al 2017;Hawken et al 2017;Hamaus et al 2017;Correa et al 2019;Achitouv 2019;Hawken et al 2020;Hamaus et al 2020;Nadathur et al 2020;Correa et al 2022;Aubert et al 2022), weak lensing (Melchior et al 2014;Clampitt & Jain 2015;Chantavat et al 2016;Gruen & Dark Energy Survey Collaboration 2016;Chantavat et al 2017;Cai et al 2017;Sánchez et al 2017b;Baker et al 2018;Brouwer et al 2018;Fang et al 2019;Vielzeuf et al 2021;Davies et al 2021;Bonici et al 2022), the integrated Sa...…”

“…We note that we leave for future work the measurement of the void size function in the photometric galaxy distribution from Euclid, for which the data treatment greatly differs from the spectroscopic one (see e.g. Pollina et al 2019 andBonici et al 2022).…”

Why Cosmic Voids Matter: Nonlinear Structure & Linear Dynamics

“…This opens up a vast observational window to conduct cosmological experiments, allowing us to make use of voids ranging from a few (or possibly less) to hundreds of Mpc in diameter. As linear dynamics holds up in all voids irrespective of their size, void catalogs can not only be extended via enlarging survey volumes towards higher redshifts (as planned for a number of next-generation surveys, such as Euclid [126][127][128]), but also by conducting deeper observations that provide denser tracer samples and hence smaller sub-voids (e.g., as planned for Roman [129] and 4MOST [130]), even at low redshift. This would open up the possibility to maximize the number of observable linear modes of the density field of large-scale structure that can be exploited for the purpose of cosmological inference, far beyond the previously imposed limits.…”