MR 2251-178 and PG 1126-041 are two nearby QSOs hosting Ultra Fast Outflows (UFOs), consisting of high-speed (~ a tenth of the speed of light) ionised winds detected in X-ray at sub-pc scales. We used MUSE AO-assisted data (narrow field mode) to study the large-scale properties of the ionised wind, with the purpose of relating the outflows on different physical scales in order to better constrain the wind propagation mechanism. Our results suggest momentum-driven wind propagation, whereas an energy-driven mechanism is excluded unless ~ 100x additional momentum is locked in a molecular or atomic gas phase (not visible with MUSE). We also collected data from the literature for nearby QSOs hosting both UFOs and large-scale outflows and showed that the wind seem to lie systematically in either a momentum or an energy-driven regime, indicating that these two models bracket the physics of AGN-driven winds very well.

Massive spiral galaxies in the nearby Universe appear to host a considerable fraction of baryons - or, equivalently, have low dark matter fraction - within their disc (check it out here). Is this evidence backed up by most recent theoretical models of galaxy formation and evolution? We tried to answer this question by studying a sample of simulated massive spirals extracted from the cosmological hydrodynamical models EAGLE and IllustrisTNG. We found that discrepancies between simulated and real galaxies of similar stellar masses arise on both global and local scales. On the scales of the halos, the simulated discs show a factor ~2-4 more dark matter than real galaxies. On the scales of their discs, the simulated galaxies encloses a factor ~2 more dark matter than real galaxies. Such a mismatch in the disc-halo connection at high-masses is probably caused by an overly-efficient negative feedback in the simulations, which does not seem to occur in the real Universe (the so called "failed feedback" problem).

NEW! -> Download images and rotation curves for massive discs in EAGLE and IllustrisTNG here

In the last two decades, deep HI observations of nearby late-type galaxies have revealed the presence of extra-planar HI layers extending up to a few kpc above the galaxy midplane and accounting for ~10% of the total HI content. In the few cases studied in detail, these HI layers were found to be characterised by a slow-rotating, globally inflowing kinematics, which is expected by gas in a galactic fountain cycle triggered by stellar feedback.

We now present a homogenous and detailed analysis for a sample of 13 late-type galaxies with deep HI observations from the HALOGAS project. For each system we have masked out the HI emission coming from the rotating thin disk and produced synthetic data-cubes to model the leftover extra-planar emission. Our model features 3 structural and 4 kinematical global parameters, which are fit to the data via a Bayesian MCMC method.

We found that extra-planar HI layers are ubiquitous in disc galaxies, with HI masses that are in excellent agreement with predictions from simple models of galactic fountain powered by stellar feedback. In most cases, the kinematics show a global inflow with speed of 20-30 km/s in the vertical and radial directions, along with a vertical rotational lag of 5-20 km/s/kpc, suggesting an interaction between the material outflowing from the disc and the circumgalactic medium.


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The local mismatch

Stellar-to-total mass enclosed with a given radius R, as a function of R, for the simulated and the observed samples. Within their disc, nearby spirals show a factor ~2 higher stellar fraction compared to simulated galaxies.