C. Melioli

Magnetic Fields in Diffuse Media

Future Observations of Cosmic Magnetic Fields with LOFAR, SKA and its precursors.- Magnetic fields with the Atacama Large Millimeter/submillimeter Array.- Synchrotron radiation and Faraday rotation.- Interstellar Grain Alignment - Observational Status.- Magnetic Field Measurement with Ground State Alignment.- Kinetic Turbulence.- Interstellar Polarization and Magnetic Turbulence.- MHD Turbulence and its Implications.- The intermittency of ISM turbulence : what do the observations tell us?.- Ambipolar Diffusion.- Magnetic Reconnection in Astrophysical Environments.- Interstellar MHD Turbulence and Star Formation.- Observations of Magnetic Fields in Molecular Clouds-Testing Star Formation Theory.- Magnetic Fields in Star Formation.- Particle Acceleration by Magnetic Reconnection.- Cosmic Ray transport in turbulent magnetic field.- Magnetic Fields in the Milky Way.- Magnetic fields in galaxies.- Simulations of galactic dynamos.- Cosmic rays in galaxy clusters and their interaction with magnetic fields.- Turbulence in the intracluster medium.

Hydrodynamical simulations of Galactic fountains II: evolution of multiple fountains

The ejection of gas out of the disk in late-type galaxies is related to star formation and is mainly due to the explosion of Type II supernovae. In a previous paper, we considered the evolution of a single Galactic fountain, that is, a fountain powered by a single supernova cluster. Using 3D hydrodynamical simulations, we studied in detail the fountain flow and its dependence with several factors, such as the Galactic rotation, the distance to the Galactic center, and the presence of a hot gaseous halo. As a natural follow-up, the present paper investigates the dynamical evolution of multiple generations of fountains generated by � 100 OB associations. We have considered the observed size-frequency distribution of young stellar clusters within the Galaxy in order to appropriately fuel the multiple fountains in our simulations. Most of the results of the previous paper have been confirmed, like for example the formation of intermediate velocity clouds above the disk by the multiple fountains. Also, the present work confirms the localized nature of the fountain flows: the freshly ejected metals tend to fall back close to the same Galactocentric region where they are delivered. Therefore, the fountains do not change significantly the radial profile of the disk chemical abundance. The multiple fountains simulations also allowed to consistently calculate the feedback of the star formation on the halo gas. We found that the hot gas gains about 10 % of all the SNII energy produced in the disk. Thus, the SN feedback more than compensate for the halo radiative losses and allow for a quasi steady-state disk-halo circulation to exist. Finally, we have also considered the possibility of mass infall from the intergalactic medium and its interaction with the clouds that are formed by the fountains. Though our simulations are not suitable to reproduce the slow rotational pattern that is typically observed in the halos around the disk galaxies, they indicate that the presence of an external gas infall may help to slow down the rotation of the gas in the clouds and thus the amount of angular momentum that they transfer to the coronal gas, as previously suggested in the literature.

GAS OUTFLOWS IN SEYFERT GALAXIES: EFFECTS OF STAR FORMATION VERSUS AGN FEEDBACK

Large scale, weakly collimated outflows are very common in galaxies with large infrared luminosities. In complex systems in particular, where intense star formation (SF) coexists with an active galactic nucleus (AGN), it is not clear yet from observations whether the SF, the AGN, or both are driving these outflows. Accreting supermassive black holes (SMBHs) are expected to influence their host galaxies through kinetic and radiative feedback processes, but in a Seyfert galaxy where the energy emitted in the nuclear region is comparable to that of the body of the galaxy, it is possible that stellar activity is also playing a key role in these processes. In order to achieve a better understanding of the mechanisms driving the gas evolution specially at the nuclear regions of these galaxies, we have performed high-resolution three-dimensional hydrodynamical simulations with radiative cooling considering the feedback from both star formation regions including supernova (type I and II) explosions and an AGN jet emerging from the central region of the active spiral galaxy. We computed the gas mass lost by the system, separating the role of each of these injection energy sources on the galaxy evolution and found that at scales within one kiloparsec an outflow can be generally established considering intense nuclear star formation only. The jet alone is unable to drive a massive gas outflow, although it can sporadically drag and accelerate clumps of the underlying outflow to very high velocities.

Gas outflow in Seyfert galaxies: 3D radiative cooling hydrodynamical simulations

Accreting supermassive black holes and starburst regions influence their host galaxies through kinetic/radiative feedback processes. To better understand the gas evolution of a Seyfert galaxy, in this study we perform fully 3D hydrodynamical simulations with radiative cooling considering the presence of star formation regions, supernova feedback and small-scale (1 kpc) jet propagation in the central region of an active spiral galaxy. We compute the gas mass lost by the system and we conclude that a kpc-scale outflow is generally established only when a nuclear starburst region is coupled to a supermassive black hole jet.

Evolution of the ISM of Starburst Galaxies and the formation of galactic superwinds

The interstellar medium heated by supernova explosions (SN) may acquire an expansion velocity larger than the escape velocity and leave the galaxy through a supersonic wind. SN ejecta are transported out of the galaxies by such winds therefore affecting the chemical evolution of the galaxies. The effectiveness of the processes mentioned above depends on the heating efficiency (HE) of the SNe, and its value is still a matter of debate. We have developed a semi‐analytic model, considering the essential ingredients of a SB environment which is able to qualitatively trace the thermalisation history of the ISM in a SB region and determine the HE evolution. Our study has been also accompanied by fully 3‐D radiative cooling, hydrodynamical simulations of SNR‐SNR and SNR‐ clouds interactions. We have found that HE is very sensitive to the amount of ambient gas and clouds of the SB and may remain very small at least during part of the SB lifetime, therefore preventing or postponing the formation of a superwind. As...