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

Abstract

The role played by the large-scale structures in the galaxy evolution is not quite well understood yet. In this study, we investigate properties of galaxy in the range 0.1 < z < 0.3 from a value-added version of the WISExSCOS catalogue around cosmic filaments detected with DisPerSE. We have fitted a profile of galaxy over-density around cosmic filaments and found a typical radius of r m = 7.5 ± 0.2 Mpc. We have measured an excess of passive galaxies near the filament's spine, higher than the excess of transitioning and active galaxies. We have also detected SFR and M gradients pointing towards the filament's spine. We have investigated this result and found an M gradient for each type of galaxies: active, transitioning, and passive, and a positive SFR gradient for passive galaxies. We also link the galaxy properties and the gas content in the Cosmic Web. To do so, we have investigated the quiescent fraction f Q profile of galaxies around the cosmic filaments. Based on recent studies about the effect of the gas and of the Cosmic Web on galaxy properties, we have modelled f Q with a β model of gas pressure. The slope obtained here, β = 0.54 ± 0.18, is compatible with the scenario of projected isothermal gas in hydrostatic equilibrium (β = 2/3), and with the profiles of gas fitted in SZ.

Characterising filaments in the SDSS volume from the galaxy distribution

“…This should decrease the significance of the signal for the filament profiles detected in the galaxy distribution rather than polluting it with spurious filaments because of a reduced statistics in terms of the number of available filaments. As the SDSS footprint has a large area and the number of filaments for the analysis is high, the conclusions derived in Bonjean et al (2020) remain valid. Moreover, splitting the sample into two redshift bins (0.1 < z < 0.2 and 0.2 < z < 0.3) yielded consistent results between the two, but with lower significance.…”

“…4 but leaves the shape unaltered. After an initial peak, the number density in the survey volume is rather flat, especially in the redshift range covered by Bonjean et al (2020) Tanimura et al (2020)…”

“…Tanimura et al (2020) performed the analysis at z > 0.2 and discarded all the filaments at lower redshifts and outside of the footprint of the SDSS DR12. Bonjean et al (2020) also applied the SDSS DR12 mask, but they did not take the large holes in the footprint at low redshift (z 0.15) into account. Still, given their size, in these regions the risk is rather not to detect any filaments than to detect spurious ones.…”

“…They are probably due to spurious critical points created at the edge of the survey volume. The cuts in length of the filaments that were applied to the samples in Tanimura et al (2020) and Bonjean et al (2020) serve the purpose of eliminating these features. Figure 17 shows the distributions of the number of filaments that is connected to maxima.…”

“…DisPerSE can work with sparse datasets or with distributions of galaxies in which the density of tracers changes dramatically within the sampled volume). The catalogues of filaments described here have been used in Malavasi et al (2020), Tanimura et al (2020), Bonjean et al (2020) and represent the first published general-purpose catalogues of filaments in the SDSS obtained with the DisPerSE method. We study the systematic uncertainties deriving from the DisPerSE method and the SDSS survey characteristics.…”