The Radio and Microwave Synchrotron Foreground: Galactic Magnetic Field and Cosmc Rays
The evolution of the early Universe is encoded in the cosmic microwave background. Fundamental physics and modern cosmology are based on its study. However, part of this study is limited by large uncertainties of the Galactic diffuse microwave emission that acts as contaminating foreground.
She works on improving our knowledge of this foreground emission by modeling its single components, thereby, allowing to interpret at best available data from present space missions, such as WMAP, Planck.
The Galactic diffuse radio foreground is a superposition of different emission mechanisms: (i) synchrotron emission from cosmic-ray electrons on magnetic fields, (ii) free-free emission from interactions of thermal electrons with ionized gas, (iii) thermal radiation from interstellar dust, (iv) and anomalous microwave emission from small rapidly spinning dust grains. The problem is that properties of the interstellar medium associated to these emission mechanisms like magnetic fields, cosmic rays, thermal electrons, gas and their distribution in the Galaxy suffer from large uncertainties.
Her effort in progressively constrain these uncertainties in the modeling, especially on cosmic rays and manetic fields. The baseline was published in the following papers:
Strong, Orlando and Jaffe 2011; Orlando and Strong 2013; Jaffe et al 2013, and recent papers within the Planck collaboration.
In Strong, Orlando and Jaffe 2011 (AA, 534, 54), and later in Orlando et al 2013 (Galactic synchrotron emission with cosmic-ray propagation models MNRAS, 436, 2127), for the first time the Galactic magnetic field has been investigated in the context of CR propagation models and pysically based CR elctron distribution. In the first work she has analyzed data from different telescopes of the synchrotron emission. The best model was used for the official 9-year WMAP component separation maps. In the latter paper she found that the Galactic magnetic field is higher than usually assumed and CRs reaching 10kpc height from the Galactic plane can still come back to us. As a result the height of the Milky Way is larger than previously believed, increasing the synchrotron emission at high latitudes. The best model from her previous work was used for obtaining the officially relased Planck component separation maps (Planck collaboration X and Planck collaboration XXXI papers), in whcih work she participated in producing the official separated low frequency component maps for AME, synchrotorn and free-free. The synchrotron polarized map is shown below.
She works on improving existing models and developing new theoretical models of the diffuse radio emission components, using information from different observables. Existing knowledge from cosmic-ray measurements and gamma-ray observations are used for self-consistent predictions. Predictions can be used as baseline also for LOFAR and the forthcoming radio telescopes, such as SKA.
Further analyses, especially on caracterizing the magnetic field and cosic-ray electrons are still ongoing both idependently and within the Planck collaboration.