David Hägele   (Germany)

 haegele @ mpia.de

Doppler Imaging of Substellar Objects

 

In my PhD, I work on spatially resolving brown dwarfs and exoplanets using the Doppler imaging technique. With the James Webb Space Telescope and the advent of high spectral resolution observations with the ELT, increasingly precise measurements of atmospheres are possible, especially looking into time-variable objects. Planetary mass objects, which include large planets and brown dwarfs, are known to be variable, however, we currently lack detailed studies of this variability. To better understand this, we need better theoretical models of these variability processes.

My work is focused on the radiative transfer in these atmospheres. Specifically, I am working on software to calculate opacities of different gases called line racer and the radiative transfer software petitRADTRANS. To explain the variability observations, I work on a retrieval framework for high spectral resolution data that includes spatial distributions of different atmospheric models. Since we cannot really resolve these objects, I use the Doppler imaging technique to get spatial information. It uses the time-varying deformation of individual absorption line profiles to infer different atmospheric regions rotating in and out of view. The differences seen by this can be due to differences in chemical abundances, cloud coverage, temperature differences, and even winds.

In addition to testing this on real data, I will also use synthetic observations generated from 3D simulations of atmospheres to validate the framework against a known ground truth. Moreover, I will look into the capability of future ELT instruments for these observations and how much the precision and predictions of our models will improve.

Supervisor:    Paul Mollière (MPIA)