We present Magellan/IMACS spectroscopy of the recently discovered Milky Way satellite Tucana III (Tuc III). We identify 26 member stars in Tuc III, from which we measure a mean radial velocity of v hel = −102.3 ± 0.4 (stat.) ± 2.0 (sys.) km s −1 , a velocity dispersion of 0.1 +0.7 −0.1 km s −1 , and a mean metallicity of [Fe/H] = −2.42 +0.07 −0.08 . The upper limit on the velocity dispersion is σ < 1.5 km s −1 at 95.5% confidence, and the corresponding upper limit on the mass within the half-light radius of Tuc III is 9.0 × 10 4 M . We cannot rule out mass-to-light ratios as large as 240 M / L for Tuc III, but much lower mass-to-light ratios that would leave the system baryon-dominated are also allowed. We measure an upper limit on the metallicity spread of the stars in Tuc III of 0.19 dex at 95.5% confidence. Tuc III has a smaller metallicity dispersion and likely a smaller velocity dispersion than any known dwarf galaxy, but a larger size and lower surface brightness than any known globular cluster. Its metallicity is also much lower than those of the clusters with similar luminosity. We therefore tentatively suggest that Tuc III is the tidally-stripped remnant of a dark matter-dominated dwarf galaxy, but additional precise velocity and metallicity measurements will be necessary for a

We constrain cosmological parameters by analysing the angular power spectra of the Baryon Oscillation Spectroscopic Survey DR12 galaxies, a spectroscopic follow-up of around 1.3 million SDSS galaxies over 9,376 deg 2 with an effective volume of ∼ 6.5 (Gpc h −1 ) 3 in the redshift range 0.15 ≤ z < 0.80. We split this sample into 13 tomographic bins (∆z = 0.05); angular power spectra were calculated using a Pseudo-C estimator, and covariance matrices were estimated using log-normal simulated maps. Cosmological constraints obtained from these data were combined with constraints from Planck CMB experiment as well as the JLA supernovae compilation. Considering a wCDM cosmological model measured on scales up to k max = 0.07h Mpc −1 , we constrain a constant dark energy equation-of-state with a ∼ 4% error at the 1σ level: w 0 = −0.993 +0.046 −0.043 , together with Ω m = 0.330 ± 0.012, Ω b = 0.0505 ± 0.002, S 8 ≡ σ 8 Ω m /0.3 = 0.863 ± 0.016, and h = 0.661 ± 0.012. For the same combination of datasets, but now considering a ΛCDM model with massive neutrinos and the same scale cut, we find: Ω m = 0.328 ± 0.009, Ω b = 0.05017 +0.0009 −0.0008 , S 8 = 0.862 ± 0.017, and h = 0.663 +0.006 −0.007 , and a 95% credible interval (CI) upper limit of m ν < 0.14 eV for a normal hierarchy. These results are competitive if not better than standard analyses with the same dataset, and demonstrate this should be a method of choice for future surveys, opening the door for their full exploitation in cross-correlations probes.

We investigate the impact of prior models on the upper bound of the sum of neutrino masses, mν . Using data from large scale structure of galaxies, cosmic microwave background, type Ia supernovae, and big bang nucleosynthesis, we argue that cosmological neutrino mass and hierarchy determination should be pursued using exact models, since approximations might lead to incorrect and nonphysical bounds. We compare constraints from physically motivated neutrino mass models (i.e., ones respecting oscillation experiments) to those from models using standard cosmological approximations. The former give a consistent upper bound of mν 0.26 eV (95% CI) and yield the first approximation-independent upper bound for the lightest neutrino mass species, m ν 0 < 0.086 eV (95% CI). By contrast, one of the approximations, which is inconsistent with the known lower bounds from oscillation experiments, yields an upper bound of mν 0.15 eV (95% CI); this differs substantially from the physically motivated upper bound.

We constrain the matter density Ωm and the amplitude of density fluctuations σ8 within the ΛCDM cosmological model with shear peak statistics and angular convergence power spectra using mass maps constructed from the first three years of data of the Dark Energy Survey (DES Y3). We use tomographic shear peak statistics, including cross-peaks: peak counts calculated on maps created by taking a harmonic space product of the convergence of two tomographic redshift bins. Our analysis follows a forward-modelling scheme to create a likelihood of these statistics using N-body simulations, using a Gaussian process emulator. We take into account the uncertainty from the remaining, largely unconstrained ΛCDM parameters (Ωb, ns and h). We include the following lensing systematics: multiplicative shear bias, photometric redshift uncertainty, and galaxy intrinsic alignment. Stringent scale cuts are applied to avoid biases from unmodelled baryonic physics. We find that the additional non-Gaussian information leads to a tightening of the constraints on the structure growth parameter yielding $S_8~\equiv ~\sigma _8\sqrt{\Omega _{\mathrm{m}}/0.3}~=~0.797_{-0.013}^{+0.015}$ (68 per cent confidence limits), with a precision of 1.8 per cent, an improvement of  38 per cent compared to the angular power spectra only case. The results obtained with the angular power spectra and peak counts are found to be in agreement with each other and no significant difference in S8 is recorded. We find a mild tension of 1.5 σ between our study and the results from Planck 2018, with our analysis yielding a lower S8. Furthermore, we observe that the combination of angular power spectra and tomographic peak counts breaks the degeneracy between galaxy intrinsic alignment AIA and S8, improving cosmological constraints. We run a suite of tests concluding that our results are robust and consistent with the results from other studies using DES Y3 data.

Small temperature anisotropies in the Cosmic Microwave Background can be sourced by density perturbations via the late-time integrated Sachs-Wolfe effect. Large voids and superclusters are excellent environments to make a localized measurement of this tiny imprint. In some cases excess signals have been reported. We probed these claims with an independent data set, using the first year data of the Dark Energy Survey in a different footprint, and using a different super-structure finding strategy. We identified 52 large voids and 102 superclusters at redshifts 0.2 < z < 0.65. We used the Jubilee simulation to a priori evaluate the optimal ISW measurement configuration for our compensated top-hat filtering technique, and then performed a stacking measurement of the CMB temperature field based on the DES data. For optimal configurations, we detected a cumulative cold imprint of voids with ∆T f ≈ −5.0 ± 3.7 µK and a hot imprint of superclusters ∆T f ≈ 5.1 ± 3.2 µK ; this is ∼ 1.2σ higher than the expected |∆T f | ≈ 0.6 µK imprint of such super-structures in ΛCDM. If we instead use an a posteriori selected filter size (R/R v = 0.6), we can find a temperature decrement as large as ∆T f ≈ −9.8 ± 4.7 µK for voids, which is ∼ 2σ above ΛCDM expectations and is comparable to previous measurements made using SDSS super-structure data.