Gesa H.-M. Bertrang


Personal Details

I investigate the underlying physics by combining theory and observations!

I am an astronomer and currently Postdoctoral Researcher at Max Planck Institute for Astronomy, Heidelberg, Germany.
I am interested in polarimetry as a powerful tool to probe protoplanetary disks and star-forming regions. In my free time, after I've enjoyed the vast beauty of Chile, I am exploring the far South of Germany, now (↳photos).
On the following pages, I prepared an overview for you about myself and my research. Enjoy!


Aiming at understanding the formation of planets and low-mass stars, with a focus on the role of magnetic fields, I apply 3D radiative transfer simulations to combine theory and observations. My work is carried out in the optical, near-infrared, and (sub-)millimeter wavelength ranges.


Heidelberg, Germany
bertrang (at) mpia (dot) de
astro (at) gesabertrang (dot) com
skype: gesa.bertrang


I grew up in Kiel, in North Germany, where I later studied and earned my doctorate. I was a post-doctoral fellow at Univ. de Chile and Univ. Diego Portales in Santiago de Chile before I awarded a position as Postdoctoral Researcher at Max Planck Institute for Astronomy. I now work on Königstuhl in Heidelberg, Germany.

Upcoming talks:

2019 Oct 22 ESO, Garching, Germany

2019 Nov 9 Koblenzer Nacht der Technik (outreach), Koblenz, Germany

2019 Nov 18-20 Science of Early Life conference, Kloster Seeon, Germany

full CV

New Papers


Characterization of Ring Substructures in the Protoplanetary Disk of HD 169142 from Multi-Wavelength ALMA Observations

2019 ApJ 881 159

Intrinsic polarisation of elongated porous dust grains

2019 MNRAS 484 1211

A highly structured disk around the planet host PDS 70 revealed by high-angular resolution observations with ALMA

2019 A&A 625 118

Resolved Imaging of the AR Puppis Circumbinary Disk

2019 AJ 157 110

The Ophiuchus DIsc Survey Employing ALMA (ODISEA) - I: project description and continuum images at 28 au resolution

2019 MNRAS 482 698

Invited Talks


2019 Nov - Science of Early Life conference,  Kloster Seeon

2019 Oct - ESO,  Garching

2019 Aug - Disks2Planets workshop, Ringberg Castle

2019 Aug - NOAO, Tucson

2019 Aug - MIT, Kavli Institute

2019 Aug - Harvard, CfA

2019 Aug - Boston University, Dep. of Astronomy

2019 Aug - Turbulence & Structures workshop, Ringberg Castle

2019 Mar - Oxford, AOPP

2018 Jun - Where are the young planets? Workshop, Madrid

2018 Mar - Santiago, JAO ALMA

2017 Sep - Vienna, UniVie

2017 Jul - Lisbon, Observatory

2017 Jan - Zurich, ETHZ



My academic career


march 2011 -
september 2015
Kiel University
PhD student
Advisor: Sebastian Wolf

PhD (Dr. rer. nat.) on "Observations and simulations of polarized radiation as tracer of magnetic fields in star formation"...

october 2005 -
november 2010
Kiel University
Student (Dipl.-Phys.)
Advisor: Sebastian Wolf

Diploma in physics (Dipl.-Phys.) Thesis title: "Magnetic fields in star formation"...

Work experience

June 2018 -
May 2023
Max Planck Institute for Astronomy
Senior postdoctoral research associate
Advisor: Mario Flock

Senior postdoctoral research associate in the UFOS group ( at Max Planck Institute for Astronomy....

march 2017 -
march 2018
Universidad de Chile
Advisor: Laura Perez

Grant (~125,000 USD) from the Chilean government to carry out independent research, hosted at Universidad de Chile (w Laura Perez)....

october 2015 -
march 2017
U de Chile & U Diego Portales
MAD Fellow
Advisors: Simon Casassus & Lucas Cieza

Grant (~112,000 USD) to carry out independent research within the Millenium ALMA Disk nucleus (MAD), hosted at Universidad de Chile (w Simon Casassus) and Universidad Diego Portales (w Lucas Cieza)....

full CV


What I do

Young stars are surrounded by disks of dust and gas. These circumstellar disks are the birthplaces of planets. Understanding the physical processes in these disk is vital for the understanding of planet formation. It has been predicted that magnetic fields are an important factor on a wide range of physical processes in protoplanetary disks, such as the migration of planet(esimals) and the mere evolution of disks. Yet, observational constraints are still pending. In the classical picture, (sub-)mm continuum polarisation is the tracer for magnetic fields in disks. Aspherical dust grains, whose thermal emission is intrinsically polarized, get aligned by the magnetic field due to radiative torques. In recent years, however, this picture has been challenged. New theoretical studies show that (sub-)mm continuum polarisation can also be created by scattering of the thermal dust emission or arise from aspherical grains which are aligned by the radiation field rather than the magnetic field. These three mechanisms trace fundamentally different physics in protoplanetary disks, yet, their polarisation predictions are not clearly distinguishable. I am applying 3D radiative transfer simulations of the polarized continuum and gas emission in combination with observations to disentangle the different mechanisms behind the measured polarization aiming at constraining magnetic fields in protoplanetary disks.

Publications: Bertrang 2015 (PhD thesis); Bertrang+2017; Bertrang & Wolf 2017; Flock+2017

As planets form and grow in dusty, gaseous circumstellar disks, mutual gravitational interactions between disk and planet lead to a series of phenomena such as gaps, warps, or spiral arms. I make use of multi-wavelength observations performed with VLT/SPHERE and ALMA  in combinations with radiative transfer simulations to  test for signals of this interaction.

Publications: Bertrang+2018; Xu+2015; Cieza+2017; Avenhaus+2018; Cieza+2019

The role of magnetic fields in the process of star formation is a matter of continuous debate. Clear observational proof of the general influence of magnetic fields on the early phase of cloud collapse is still pending. Multi-wavelength polarimetry (optical - mm), tracing magnetic fields on scales of 10^3-10^6au in Bok globules, reveal a strong polarization signal and strongly aligned polarization vectors on large scales (Bertrang+2014, Jorquera & Bertrang 2018). This indicates dominant magnetic fields across Bok globules with simple as well as complex density structures. To reconcile our findings in globules, the lowest mass clouds known, and the results on intermediate (e.g., Taurus) and more massive (e.g., Orion) clouds, we postulate a mass dependent role of magnetic fields, whereby magnetic fields appear to be dominant on low and high mass but rather sub-dominant on intermediate mass clouds.

Publications: Bertrang+2014; Bertrang 2015 (PHD thesis); Jorquera & Bertrang 2018

Mentoring: I am co-supervisor of two PhD students, Lizxandra Flores and Marcelo Barraza (MPIA). At U de Chile, I supervised the Bachelor student Sebastian Jorquera, together we published our work on magnetic fields in Bok globules (Jorquera & Bertrang 2018).

Teaching: I am experienced as teaching assistant of several courses on undergrad level at Kiel University (Physics IV: nuclear physics, particle physics, astrophysics and cosmology; Elementary mathematical methods in physics I & II).

  I enjoy talking science not only with scientist but just as much with the public. Upcoming and past outreach events are:

- 2020 Jan: Talk at "Faszination Astronomie" at HdA, Heidelberg
- 2019 Nov: Talk at the Koblenz Technology Night, Koblenz
- 2019 Jul:  Talk to the 50thanniversary of MPIA at HdA, Heidelberg
- 2019 Jan: Talk at Astronomy on Tap, "Making the invisible visible", Heidelberg
- 2015 Jun: Newspaper article to the 350th anniversary of Kiel University
- 2013 Jun: Girls Day, Solar observations, Kiel University


Get in touch with me

Get in touch

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My address

skype: gesa.bertrang
phone: +49 6221 528 367

Max Planck Institute for Astronomy
Room 318
Königstuhl 17
69117 Heidelberg, Germany

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