Aims. We investigate the suitability of alpha-viscosity in self-similar models for self-gravitating disks with a focus on active galactic nuclei (AGN) disks. Methods. We use a self-similar approach to simplify the partial di ff erential equations arising from the evolution equation, which are then solved using numerical standard procedures. Results. We find a self-similar solution for the dynamical evolution of self-gravitating alpha-disks and derive the significant quantities. In the Keplerian part of the disk our model is consistent with standard stationary alpha-disk theory, and self-consistent throughout the self-gravitating regime. Positive accretion rates throughout the disk demand a high degree of self-gravitation. Combined with the temporal decline of the accretion rate and its low amount, the model prohibits the growth of large central masses. Conclusions. alpha-viscosity cannot account for the evolution of the whole mass spectrum of super-massive black holes (SMBH) in AGN. However, considering the involved scales it seems suitable for modelling protoplanetary disks.

The potential of using cluster clustering for calibrating the mass-richness relation of galaxy clusters has been recognized theoretically for over a decade. Here, we demonstrate the feasibility of this technique to achieve high-precision mass calibration using redMaPPer clusters in the Sloan Digital Sky Survey North Galactic Cap. By including cross-correlations between several richness bins in our analysis, we significantly improve the statistical precision of our mass constraints. The amplitude of the mass-richness relation is constrained to 7 per cent statistical precision by our analysis. However, the error budget is systematics dominated, reaching a 19 per cent total error that is dominated by theoretical uncertainty in the bias-mass relation for dark matter haloes. We confirm the result from Miyatake et al. that the clustering amplitude of redMaPPer clusters depends on galaxy concentration as defined therein, and we provide additional evidence that this dependence cannot be sourced by mass dependences: some other effect must account for the observed variation in clustering amplitude with galaxy concentration. Assuming that the observed dependence of redMaPPer clustering on galaxy concentration is a form of assembly bias, we find that such effects introduce a systematic error on the amplitude of the mass-richness relation that is comparable to the error bar from statistical noise. The results presented here demonstrate the power of cluster clustering for mass calibration and cosmology provided the current theoretical systematics can be ameliorated.

Terrestrial exoplanets in the canonical habitable zone may have a variety of initial water fractions due to random volatile delivery by planetesimals. If the total planetary water complement is high, the entire surface may be covered in water, forming a "waterworld." On a planet with active tectonics, competing mechanisms act to regulate the abundance of water on the surface by determining the partitioning of water between interior and surface. Here we explore how the incorporation of different mechanisms for the degassing and regassing of water changes the volatile evolution of a planet. For all of the models considered, volatile cycling reaches an approximate steady state after similar to 2 Gyr. Using these steady. states, we find that if volatile cycling is either solely dependent on temperature or seafloor pressure, exoplanets require a high abundance (greater than or similar to 0.3% of total mass) of water to have fully inundated surfaces. However, if degassing is more dependent on seafloor pressure and regassing mainly dependent on mantle temperature, the degassing rate is relatively large at late times and a steady. state between degassing and regassing is reached with a substantial surface water fraction. If this hybrid model is physical, super-Earths with a total water fraction similar to that of the Earth can become waterworlds. As a result, further understanding of the processes that drive volatile cycling on terrestrial planets is needed to determine the water fraction at which they are likely to become waterworlds.

Earths and mini Neptunes likely have a wide range of atmospheric compositions, ranging from low molecular mass atmospheres of H-2 to higher molecular atmospheres of water, CO2, N-2, or other species. Here we systematically investigate the effects of atmospheric bulk compositions on temperature and wind distributions for tidally locked sub-Jupiter-sized planets, using an idealized 3D general circulation model (GCM). The bulk composition effects are characterized in the framework of two independent variables: molecular weight and molar heat capacity. The effect of molecular weight dominates. As the molecular weight increases, the atmosphere tends to have a larger day-night temperature contrast, a smaller eastward phase shift in the thermal phase curve, and a smaller zonal wind speed. The width of the equatorial super-rotating jet also becomes narrower, and the "jet core" region, where the zonal-mean jet speed maximizes, moves to a greater pressure level. The zonal-mean zonal wind is more prone to exhibit a latitudinally alternating pattern in a higher molecular weight atmosphere. We also present analytical theories that quantitatively explain the above trends and shed light on the underlying dynamical mechanisms. Those trends might be used to indirectly determine the atmospheric compositions on tidally locked sub-Jupiter-sized planets. The effects of the molar heat capacity are generally small. But if the vertical temperature profile is close to adiabatic, molar heat capacity will play a significant role in controlling the transition from a divergent flow in the upper atmosphere to a jet-dominated flow in the lower atmosphere.

Low mass, self-gravitating accretion disks admit quasi-steady, "gravito-turbulent" states in which cooling balances turbulent viscous heating. However, numerical simulations show that gravito-turbulence cannot be sustained beyond dynamical timescales when the cooling rate or corresponding turbulent viscosity is too large. The result is disk fragmentation. We motivate and quantify an interpretation of disk fragmentation as the inability to maintain gravito-turbulence due to formal secondary instabilities driven by: (1) cooling, which reduces pressure support; and/or (2) viscosity, which reduces rotational support. We analyze the axisymmetric gravitational stability of viscous, non-adiabatic accretion disks with internal heating, external irradiation, and cooling in the shearing box approximation. We consider parameterized cooling functions in 2D and 3D disks, as well as radiative diffusion in 3D. We show that generally there is no critical cooling rate/viscosity below which the disk is formally stable, although interesting limits appear for unstable modes with lengthscales on the order of the disk thickness. We apply this new linear theory to protoplanetary disks subject to gravito-turbulence modeled as an effective viscosity, and cooling regulated by dust opacity. We find that viscosity renders the disk beyond similar to 60 au dynamically unstable on radial lengthscales a few times the local disk thickness. This is coincident with the empirical condition for disk fragmentation based on a maximum sustainable stress. We suggest turbulent stresses can play an active role in realistic disk fragmentation by removing rotational stabilization against self-gravity, and that the observed transition in behavior from gravito-turbulent to fragmenting may reflect instability of the gravito-turbulent state itself.

Because of their intense incident stellar irradiation and likely tidally locked spin states, hot Jupiters are expected to have wind speeds that approach or exceed the speed of sound. In this work, we develop a theory to explain the magnitude of these winds. We model hot Jupiters as planetary heat engines and show that hot Jupiters are always less efficient than an ideal Carnot engine. Next, we demonstrate that our predicted wind speeds match those from three-dimensional numerical simulations over a broad range of parameters. Finally, we use our theory to evaluate how well different drag mechanisms can match the wind speeds observed with Doppler spectroscopy for HD 189733b and HD 209458b. We find that magnetic drag is potentially too weak to match the observations for HD 189733b, but is compatible with the observations for HD 209458b. In contrast, shear instabilities and/or shocks are compatible with both observations. Furthermore, the two mechanisms predict different wind speed trends for hotter and colder planets than currently observed. As a result, we propose that a wider range of Doppler observations could reveal multiple drag mechanisms at play across different hot Jupiters.

The full-phase infrared light curves of low-eccentricity hot Jupiters show a trend of increasing fractional dayside-nightside brightness temperature difference with increasing incident stellar flux, both averaged across the infrared and in each individual wavelength band. The analytic theory of Komacek & Showman shows that this trend is due to the decreasing ability with increasing incident stellar flux of waves to propagate from day to night and erase temperature differences. Here, we compare the predictions of this theory with observations, showing that it explains well the shape of the trend of increasing dayside-nightside temperature difference with increasing equilibrium temperature. Applied to individual planets, the theory matches well with observations at high equilibrium temperatures but, for a fixed photosphere pressure of 100 mbar, systematically underpredicts the dayside-nightside brightness temperature differences at equilibrium temperatures less than 2000 K. We interpret this as being due to the effects of a process that moves the infrared photospheres of these cooler hot Jupiters to lower pressures. We also utilize general circulation modeling with double-gray radiative transfer to explore how the circulation changes with equilibrium temperature and drag strengths. As expected from our theory, the dayside-nightside temperature differences from our numerical simulations increase with increasing incident stellar flux and drag strengths. We calculate model phase curves using our general circulation models, from which we compare the broadband infrared offset from the substellar point and dayside-nightside brightness temperature differences against observations, finding that strong drag or additional effects (e.g., clouds and/or supersolar metallicities) are necessary to explain many observed phase curves.

Small solids embedded in gaseous protoplanetary disks are subject to strong dust-gas friction. Consequently, tightly coupled dust particles almost follow the gas flow. This near conservation of the dust-to-gas ratio along streamlines is analogous to the near conservation of entropy along flows of (dust-free) gas with weak heating and cooling. We develop this thermodynamic analogy into a framework to study dusty gas dynamics in protoplanetary disks. We show that an isothermal dusty gas behaves like an adiabatic pure gas, and that finite dust-gas coupling may be regarded as effective heating/cooling. We exploit this correspondence to deduce that (1) perfectly coupled, thin dust layers cannot cause axisymmetric instabilities; (2) radial dust edges are unstable if the dust is vertically well-mixed; (3) the streaming instability necessarily involves a gas pressure response that lags behind dust density; and (4) dust-loading introduces buoyancy forces that generally stabilize the vertical shear instability associated with global radial temperature gradients. We also discuss dusty analogs of other hydrodynamic processes (e.g., Rossby wave instability, convective overstability, and zombie vortices) and how to simulate dusty protoplanetary disks with minor tweaks to existing codes for pure gas dynamics.

We investigate the orbital evolution of an initially thin stellar disc around a supermassive black hole, considering various perturbative sources of gravity. By means of direct numerical N-body modelling, we first focus on the case when the disc is embedded in an extended spherically symmetric star cluster. We find that the gravitational influence of the disc triggers formation of macroscopic non- spherical substructure in the cluster which, subsequently, significantly affects the evolution of the disc itself. In another approximation, when the cluster is emu- lated by an analytic spherically symmetric potential, we further consider pertur- bative gravitational influence of a distant axisymmetric source. Using standard perturbation methods, we derive a simple semi-analytic model for such a config- uration. It turns out that the additional axisymmetric potential leads to mutual gravitational coupling of the individual orbits from the disc. Consequently, the dense parts of the disc can, for some period of time, evolve coherently. Finally, we apply some of our results to the young stellar disc which is observed in the innermost parsec of the Galactic Centre. 1

Title: Shell galaxies: kinematical signature of shells, satellite galaxy disruption and dynamical friction Author: Ivana Ebrová Department / Institute: Astronomical Institute of the Academy of Sciences of the Czech Republic Supervisor of the doctoral thesis: RNDr. Bruno Jungwiert, Ph.D., Astronomical Institute of the Academy of Sciences of the Czech Republic Abstract: Stellar shells observed in many giant elliptical and lenticular as well as a few spiral and dwarf galaxies presumably result from radial minor mergers of galaxies. We show that the line-of-sight velocity distribution of the shells has a quadruple-peaked shape. We found simple analytical expressions that connect the positions of the four peaks of the line profile with the mass distribution of the galaxy, namely, the circular velocity at the given shell radius and the propagation velocity of the shell. The analytical expressions were applied to a test-particle simulation of a radial minor merger, and the potential of the simulated host galaxy was successfully recovered. Shell kinematics can thus become an independent tool to determine the content and distribution of dark matter in shell galaxies up to ~100 kpc from the center of the host galaxy. Moreover we investigate the dynamical friction and gradual disruption of the cannibalized galaxy...