- Multi-wavelength studies of Nearby Galaxies from low to high frequencies
The interstellar medium (ISM) is the multi-phase environment from which stars are formed, therefore it is extremely important for the formation and evolution of galaxies. Its multi-phase nature calls for multi-wavelength observations to trace its different components, from the most abundant, hydrogen in different phases (from hot ionized to cold molecular gas), to dust, cosmic rays and magnetic fields.
Nearby galaxies offer the opportunity to study the role of the ISM, and its different components, on star formation on large scales, while still being close enough to reveal the local details, thanks to the unprecedented combination of sensitivity and resolution offered by the current observational facilities. We are involved in studies of star formation processes through different tracers, exploiting the most powerful radio facilities currently available, such as ALMA, VLA, and LOFAR.
- Magnetic fields and cosmic rays role in star formation
Magnetic fields play an important role in the ISM of spiral galaxies: they contribute to the total pressure, influence star formation processes at every scale, and may also affect the formation of spiral arms and outflows. They have typically been observed through synchrotron emission in total intensity and polarization. This emission is generally associated with massive star-formation processes: massive stars end their lives in supernovae explosions accelerating ultra-relativistic electrons, which spiral in the magnetic field. A new perspective on the study of magnetic fields in nearby galaxies is now made available by the unprecedented combination of high resolution and sensitivity in full polarization mode offered by ALMA, which enables to map the structure of interstellar magnetic fields in the cold gas of nearby galaxies, through observations of dust continuum polarization at the scale of giant molecular clouds. This is crucial to understand how magnetic fields influence gas dynamics and in particular their role in regulating star formation, driving galactic outflows and fueling galactic nuclei.
- Environmental effects on gas removal and star formation
Gravitational interactions between galaxies lead to asymmetric gas flows, compression, shear, enhanced turbulence and outflows, which can modify the structure of galaxies and their star formation processes. A multi-wavelength study of nearby compact groups, relating the observed morphological and kinematic disturbances of group members, their star formation activity and history with the evolutionary history of the groups, is essential. Radio observations at low frequencies, allow to study the low-energy relativistic electron population, tracing the non-thermal radio emitting structures further away from the areas of relativistic particle supply, like in the halos or in tidal tails. The involvement of IRA researchers in LOFAR gives access to new low-frequency data on nearby compact groups. Galaxies in denser environments are affected by ram pressure stripping (RPS) of disk gas, due to interaction between the galaxy ISM and the intergalactic medium. Neutral gas studies have proved the efficiency of RPS in clusters of galaxies, but also tracers of other gas phases (e.g., Hα emission, X-ray) and even of young stars (UV, blue light) are used as complementary methods. At IRA, much interest is given to the presence of molecular gas in RPS tails, recently observed thanks to the high sensitivity provided by ALMA, but also to the possible radio continuum emission in the tails.
Contacts: R. Paladino (email@example.com)