1607.01406
Evolution of cosmic filaments and of their galaxy population from NHD cosmological simulations
Heller, et al
Despite containing about a half of the total matter in the Universe, at most wavelengths the filamentary structure of the cosmic web is difficult to observe. In this work, use large unigrid cosmological sims to investigate how the geometrical, thermodynamical and magnetic properties of cosmo filaments vary with mass and redshift (z<=1). Find that the average temperature, length, volume and magnetic field of filaments are tightly log-log correlated with the underlying total gravitational mass. This reflects the role of self-gravity in shaping their properties of the simulated population of galaxy-sized haloes within filaments, and compare their properties to the results obtained from the spectroscopic GAMA survey. Simulated and observed filaments with the same length are found to contain an equal number of galaxies, with very similar distribution of halo masses. The total number of galaxies within each filament and the total/average stellar mass in galaxies can now be used to predict also the large-scale properties of the gas in the host filaments across tens of hundreds of Mpc in scale. These results are the first steps towards the future use of galaxy catalogues in order to select the best targets for observations of the warm-hot IGM.
1607.01761
Looking through the same lens: shear calibration for LSST, Euclid & WFIRST with stage 4 CMB lensing
Sichuan, Krause, Eifel, Doré, Miyatake, Rhodes, Spergel
The next generation WL surveys (LSST, Euclid, WFIRST) will require exquisite control over systematic effects. In this paper, address shear calibration and present the most realistic forecast to date for LSST/Euclid/WFIRST and CMB lensing from a stage 4 CMB experiment (CMB S4). Use the CosmoLike code to simulate a joint analysis of all the 2pt functions of galaxy density, galaxy shear and CMB lensing convergence. Include the full Gaussian and non-Gaussian covariances and explore the resulting joint likelihood with MCMC. Constrain shear calibration biases while simultaneously varying cosmo parameters, galaxy biases and photo-z uncertainties. Find that CMB lensing from CMB S4 enables the calibration of the shear biases down to 0.2%-3% in 10 tomographic bins for LSST (below the ~0.5% requirements in most tomographic bins), down to 0.4%-2.4% in 10 bins for Euclid and 0.6%-3.2% in 10 bins for WFIRST. For a given lensing survey, the method works best at high z where shear calibration is otherwise most challenging. This self-calibration is robust to Gaussian photo-z uncertainties and to a reasonable level of intrinsic alignment. It is also robust to changes in the beam and the effectiveness of the component separation of the CMB experiment, and slowly dependent on its depth, making it possible with third generation CMB experiments such as AdvACT and SPT-3G, as well as the Simons Observatory.
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