We study the spatially resolved (sub-kpc) gas velocity dispersion($\sigma$)--star formation rate (SFR) relation in the FIRE-2 (Feedback inRealistic Environments) cosmological simulations. We specifically focus onMilky Way mass disk galaxies at late times. In agreement with observations, wefind a relatively flat relationship, with $\sigma \approx 15-30$ km/s inneutral gas across 3 dex in SFRs. We show that higher dense gas fractions(ratios of dense gas to neutral gas) and SFRs are correlated at constant$\sigma$. Similarly, lower gas fractions (ratios of gas to stellar mass) arecorrelated with higher $\sigma$ at constant SFR. The limits of the$\sigma$-$\Sigma_{\rm SFR}$ relation correspond to the onset of strongoutflows. We see evidence of "on-off" cycles of star formation in thesimulations, corresponding to feedback injection timescales of 10-100 Myr,where SFRs oscillate about equilibrium SFR predictions. Finally, SFRs andvelocity dispersions in the simulations agree well with feedback-regulated andmarginally stable gas disk (Toomre's $Q =1$) model predictions, and the dataeffectively rule out models assuming that gas turns into stars at (low)constant efficiency (i.e., ${\rm 1\%}$ per free-fall time). And although thesimulation data do not entirely exclude gas accretion/gravitationally poweredturbulence as a driver of $\sigma$, it appears to be strongly subdominant tostellar feedback in the simulated galaxy disks.

We study the correlation of orbital poles of the 11 classical satellitegalaxies of the Milky Way, comparing results from previous proper motions withthe independent data by Gaia DR2. Previous results on the degree of correlationand its significance are confirmed by the new data. A majority of thesatellites co-orbit along the Vast Polar Structure, the plane (or disk) ofsatellite galaxies defined by their positions. The orbital planes of eightsatellites align to $<20^\circ$ with a common direction, seven even orbit inthe same sense. Most also share similar specific angular momenta, though theirwide distribution on the sky does not support a recent group infall orsatellites-of-satellites origin. The orbital pole concentration hascontinuously increased as more precise proper motions were measured, asexpected if the underlying distribution shows true correlation that is washedout by observational uncertainties. The orbital poles of the up to seven mostcorrelated satellites are in fact almost as concentrated as expected for thebest-possible orbital alignment achievable given the satellite positions.Combining the best-available proper motions substantially increases the tensionwith $\Lambda$CDM cosmological expectations: <0.1 per cent of simulatedsatellite systems in IllustrisTNG contain seven orbital poles as closelyaligned as observed. Simulated systems that simultaneously reproduce theconcentration of orbital poles and the flattening of the satellite distributionhave a frequency of <0.1 per cent for any number of k > 3 combined orbitalpoles, indicating that these results are not affected by a look-elsewhereeffect. This compounds the Planes of Satellite Galaxies Problem.

We present the constraints on the helium abundance in 12 X-ray luminousgalaxy clusters that have been mapped in their X-ray and Sunyaev-Zeldovich (SZ)signals out to $R_{200}$ for the XMM-Newton Cluster Outskirts Project (X-COP).The unprecedented precision available for the estimate of $H_0$ allows us toinvestigate how much the reconstructed X-ray and SZ signals are consistent withthe expected ratio $x$ between helium and proton densities of 0.08-0.1. We findthat a $H_0$ around 70 km/s/Mpc is preferred from our measurements, with lowervalues of $H_0$ as requested from the Planck collaboration (67 km/s/Mpc)requiring a 34% higher value of $x$. On the other hand, higher values of $H_0$,as obtained by measurements in the local universe, impose $x$, from theprimordial nucleosynthesis calculations and current solar abundances, reducedby 37--44\%.