Osservatorio Astrofisico di Catania

Magnetic instabilities and angular momentum transport in red giant core
2026-03-23 11:00 - 12:30 UTC | Sede A. Riccò, Via Santa Sofia 78, Catania
Recording: https://www.oact.inaf.it/seminars/
DATE: Monday, March 23, 11:00 a.m.
ORGANIZER: INAF-OACT
LOCATION: AULA OVEST (INAF-OACT) + remote
Link for the remote audience:https://meet.google.com/wvf-uwxo-oyj
SPEAKER: Domenico Giovanni Meduri (INAF)
ABSTRACT:The stability of magnetic fields in radiative stellar interiors remains a fundamental open question in understanding the rotational and chemical evolution of low-mass stars. Recent high-resolution asteroseismic observations of red giants have revealed unexpectedly slow core rotations and the presence of strong internal magnetic fields, opening a new window on the internal dynamics of evolved stars. In this talk, I will review the main magnetohydrodynamic instabilities expected in radiative stellar interiors and present new 3D direct numerical simulations of the Tayler instability, a kink-type instability of toroidal magnetic fields prevalent in these regions. By combining simulations, linear stability analysis, and stellar evolution models, we identify where and under what conditions the Tayler instability is likely to operate in red giant cores. These results provide new insight into angular momentum transport in evolved low-mass stars and may also have broader implications for other stars with radiative interiors.

A few rules:— before joining, make sure you are using your institutional inaf.it account if you have one (otherwise we will grant you permission to join)— please do not forget to mute your microphone and switch off your webcam when access the virtual room— for questions leave a message in the chat, the answers at the end of the webinar— the seminar will be recorded, so if you are interested in it, please contact us to get the link to the registration.

The Nature of Polarized Sources in the MIGHTEE XMM-LSS Deep Field
2026-05-20 11:30 - 12:30
Recording: NOT AVAILABLE
DATE: Wednesday, May 20, 11:30 a.m.
ORGANIZER: INAF-OACT
LOCATION: AULA OVEST (INAF-OACT) + remote
Link for the remote audience:https://meet.google.com/wvf-uwxo-oyj
SPEAKER: Lennart Heino (INAF)
ABSTRACT:This study explores the polarized emission of the faint extragalactic radio sources in the MIGHTEE (MeerKAT International Giga-Hertz Tiered Extragalactic Exploration, Jarvis et al., 2016) survey in order to systematically study cosmic magnetic fields in galaxies to high redshift. Reaching a sensitivity of 1.5 µJy/beam at a resolution of 5 arcseconds, MIGHTEE is providing an opportunity to chart the evolution of polarized emission from distant galaxies over cosmic time.
The MIGHTEE survey detects polarized emission for a large number of radio sources down to total intensity flux densities of the order of 100 µJy. At these flux densities the source population is increasingly dominated by star-forming galaxies (SFGs) as opposed to active galactic nuclei (AGNs). While polarized emission of AGN can be traced to very distant galaxies, polarized emission of SFGs at moderate distance has been detected only once.
I use multi-wavelength criteria to classify MIGHTEE radio objects as either SFG or AGN. I perform Rotation Measure Synthesis (RMSY) on the spectro-polarimetric data cubes and use the polarization and RMSY spectra to search for polarized emission. A comparative analysis of the polarization properties of SFGs and AGNs is performed. The analysis is extended to the lowest possible flux densities using stacking techniques. I will show preliminary results of the MeerKAT polarization studies of radio sources down to a sensitivity at the micro-Jansky level.

A few rules:— before joining, make sure you are using your institutional inaf.it account if you have one (otherwise we will grant you permission to join)— please do not forget to mute your microphone and switch off your webcam when access the virtual room— for questions leave a message in the chat, the answers at the end of the webinar
