COSMOS2015 photometric redshifts probe the impact of filaments on galaxy properties

Abstract

The variations of galaxy stellar masses and colour-types with the distance to projected cosmic filaments are quantified using the precise photometric redshifts of the COSMOS2015 catalogue extracted from COSMOS field (2 deg 2 ). Realistic mock catalogues are also extracted from the lightcone of the cosmological hydrodynamical simulation HORIZON-AGN. They show that the photometric redshift accuracy of the observed catalogue (σ z < 0.015 at M * > 10 10 M and z < 0.9) is sufficient to provide 2D filaments that closely match their projected 3D counterparts. Transverse stellar mass gradients are measured in projected slices of thickness 75 Mpc between 0.5 < z < 0.9, showing that the most massive galaxies are statistically closer to their neighbouring filament. At fixed stellar mass, passive galaxies are also found closer to their filament while active star-forming galaxies statistically lie further away. The contributions of nodes and local density are removed from these gradients to highlight the specific role played by the geometry of the filaments. We find that the measured signal does persist after this removal, clearly demonstrating that proximity to a filament is not equivalent to proximity to an over-density. These findings are in agreement with gradients measured both in 2D or 3D in the HORIZON-AGN simulation and those observed in the spectroscopic VIPERS survey (which rely on the identification of 3D filaments). They are consistent with a picture in which the influence of the geometry of the large-scale environment drives anisotropic tides which impact the assembly history of galaxies, and hence their observed properties.

Filament profiles from WISExSCOS galaxies as probes of the impact of environmental effects

“…Galaxies are significantly ∼ 10% more massive, and ∼ 10% less star-forming. This trend is expected since the excess of passive galaxies near the filaments spines was already shown in several studies (e.g., Malavasi et al 2017;Laigle et al 2018;Kraljic et al 2018;Sarron et al 2019). This implies a different ratio of passive over active galaxies with increasing distance to the filaments' spine, producing these gradients.…”

Anisotropic infall in the outskirts of OmegaWINGS galaxy clusters

“…Using the Sloan Digital Sky Survey (SDSS, York et al 2000), Chen et al (2017) find that at the same local density, galaxies that reside closer to filaments are more massive than those further out, in agreement with Alpaslan et al (2016) and Laigle et al (2018). Using the same survey, but at intermediate redshifts, 0.12 < z < 0.40, Zhang et al (2013) detect an evolution in the blue fraction of filament galaxies located in between pairs of clusters, that is not observed in clusters.…”

“…Using the same survey, Alpaslan et al (2016) have found that isolated spiral galaxies have higher stellar masses and lower SFR towards the inner regions of filaments than in the filament periphery. Similarly, Laigle et al (2018) study the properties of galaxies with photo-metric redshifts in the range 0.5 < z phot < 0.9 and find that, at fixed stellar mass, passive galaxies are more confined towards the core of filaments.…”

Multipolar moments of weak lensing signal around clusters

“…Their dynamical evolution probes the underlying cosmological model. They also play an important environmental role on galaxy formation and galaxy properties (Hahn et al 2007;Sousbie et al 2008;Pichon et al 2011;Codis et al 2012;Malavasi et al 2017;Laigle et al 2017). However, given the low-density contrast of filaments, identifying them in observations has remained a challenge and, in this context, several observables have been devised to probe their mass distribution.…”