Extremely Large Telescope

Abstract:

The upcoming WEAVE-QSO survey will target a high density of quasars over a large area, enabling the reconstruction of the 3D density field through Lyman-훼 tomography over unprecedented volumes smoothed on intermediate cosmological scales (≈ 16 Mpc/h). We produce mocks of the Lyman-훼 forest using LyMAS, and reconstruct the 3D density field between sightlines through Wiener filtering in a configuration compatible with the future WEAVE-QSO observations. The fidelity of the reconstruction is assessed by measuring one- and two-point statistics from the distribution of critical points in the cosmic web. In addition, initial Lagrangian statistics are predicted from first principles, and measurements of the connectivity of the cosmic web are performed. The reconstruction captures well the expected features in the auto- and cross-correlations of the critical points. This remains true after a realistic noise is added to the synthetic spectra, even though sparsity of sightlines introduces systematics, especially in the cross-correlations of points with mixed signature. Specifically, the most striking clustering features involving filaments and walls could be measured with up to 4 sigma of significance with a WEAVE-QSO-like survey. Moreover, the connectivity of each peak identified in the reconstructed field is globally consistent with its counterpart in the original field, indicating that the reconstruction preserves the geometry of the density field not only statistically, but also locally. Hence the critical points relative positions within the tomographic reconstruction could be used as standard rulers for dark energy by WEAVE-QSO and similar surveys.

Abstract:

We explore a sample of 1492 galaxies with measurements of the mean stellar population properties and the spin parameter proxy, λRe⁠, drawn from the SAMI Galaxy Survey. We fit a global [α/Fe]–σ relation, finding that [α/Fe]=(0.395±0.010)log10(σ)−(0.627±0.002)⁠. We observe an anti-correlation between the residuals Δ[α/Fe] and the inclination-corrected λeoRe⁠, which can be expressed as Δ[α/Fe]=(−0.057±0.008)λeoRe+(0.020±0.003)⁠. The anti-correlation appears to be driven by star-forming galaxies, with a gradient of Δ[α/Fe]∼(−0.121±0.015)λeoRe⁠, although a weak relationship persists for the subsample of galaxies for which star formation has been quenched. We take this to be confirmation that disc-dominated galaxies have an extended duration of star formation. At a reference velocity dispersion of 200 km s−1, we estimate an increase in half-mass formation time from ∼0.5 Gyr to ∼1.2 Gyr from low- to high-λeoRe galaxies. Slow rotators do not appear to fit these trends. Their residual α-enhancement is indistinguishable from other galaxies with λeoRe⪅0.4⁠, despite being both larger and more massive. This result shows that galaxies with λeoRe⪅0.4 experience a similar range of star formation histories, despite their different physical structure and angular momentum.