Cosmology and the Dusty Universe via VST ATLAS and ALMA

Abstract

Clustering analyses of the large-scale structure of the Universe provide a powerful tool for testing the current standard model of cosmology (ΛCDM). To this end, we exploit the multi-band optical imaging from the VST ATLAS survey, which covers ~4700 deg^2 of the southern sky. Our main goals are to create a galaxy cluster catalogue and use it to test the predictions of ΛCDM; to use the cross-correlation of various ATLAS galaxy samples with the CMB as a probe dark energy, and to study star formation in the most massive halos in the early Universe which are the progenitors of present-day clusters. We find the ATLAS galaxy cluster catalogue to be more complete than the SDSS RedMapper cluster sample at z<0.35. We use this catalogue to improve the completeness of the Planck SZ cluster sample by identifying 11 SZ sources with no confirmed optical counterparts, for which we obtain spectroscopic redshifts and cluster mass measurements. The ATLAS cluster mass functions prefer a value of S8=σ8sqrt(Ωm/0.3)=0.77±0.03, which is in good agreement with various other low-redshift analyses of the large-scale structure, but ~2σ lower than the latest Planck CMB measurement. We then measure the Integrated Sachs-Wolfe (ISW) effect based on the cross-correlation of ATLAS galaxies and the Planck CMB temperature map. Combining our results with previous measurements from SDSS, we detect the ISW signal at 2.6σ at z<0.55, in agreement with the ΛCDM model. However, at z=0.68, we find the measured ISW amplitude to be ~2σ lower than the ΛCDM predictions. Future confirmation of these results based on SKA, DESI or LSST observations, could open the door to alternatives to dark energy, including modified gravity. Finally, using ALMA observations of four z>6 and two z~2.5 sub-mm galaxies, we demonstrate that AGN rather than star formation, are the dominant dust-heating mechanism in these sources.