Coffee talks
Friday 09/10/2020 @ 11:30, On-line - meet.google.com/sue-bwvk-axf
Andrea Bracco (Rudjer Boškovic Institute), "The multiphase and magnetized neutral hydrogen seen by LOFAR"
LOFAR data below 200 MHz are revealing a polarized sky in the radio that looks much more complex than we thought. By means of Faraday tomography we can link the structure of these polarimetric observations to that of the magneto-ionic diffuse interstellar medium (ISM) through Faraday depth. Previous studies highlighted the remarkable association of polarized features at low radio frequencies to tracers of the magnetized-neutral ISM, as interstellar dust and atomic hydrogen (HI). However, the physical conditions responsible for the correlation between magneto-ionic and neutral media are yet to be clarified. In this talk I will first introduce the questions behind the study of structure formation in the multiphase and magnetized ISM and I will present a very recent work that tackles the correlation between LOFAR data and HI spectroscopic observations at 21cm from the Effelsberg-Bonn HI Survey (EBHIS). In particular, I will present the first statistical study on the morphological correlation between LOFAR tomographic data around the 3C196 field and the multiphase HI gas decomposed in its cold, luke-warm, and warm phases. I will discuss our novel and puzzling results about the detection of a strong correlation between LOFAR and EBHIS data, where the cold HI signal appears to dominate the correlation with LOFAR over the warmer, and more ionized, HI phases. These unprecedented results might be explained in terms of non-standard physical conditions in the diffuse ISM --- large-scale compressions and shocks --- although other guidelines of interpretation are also coming along.