Image of Susanne Aalto
​Susanne Aalto, Professor of Radio Astronomy, one of two astronomers who has been awarded the prestigious ERC Advanced Grant in 2018. ​​​​​​​
Photo: ​Johan Bodell. 

Exploring the hidden nuclei of galaxies

Susanne Aalto, Professor of Radio Astronomy, is one of two astronomers at Chalmers University of Technology who has this year been awarded an ERC Advanced Grant, a prestigious award of 2.5 million euros. In the HIDDeN project, her research team will explore how supermassive black holes – like the one in the middle of the Milky Way – grow together with their host galaxies.
"Galaxies are important ‘building blocks’ for the universe's structure, and if you want to understand how the universe develops, you must understand the development of galaxies," says Susanne Aalto, professor and Head of the division Astronomy and Plasma Physics. 
The project’s name, HIDDeN, is in reference to galaxies that are enshrouded in dust and gas, often as a result of galaxy collisions and mergers. The dust and gas then act as a fuel during an extremely fast evolutionary phase, where a lot of new stars are born and black holes grow. The project is about understanding this development phase, helping to increase knowledge of the entire universe's evolution. Of particular interest for this project are hidden galaxy nuclei.
"We have discovered extremely dust-embedded galaxy nuclei that are invisible, both in normal light and in infrared radiation. We believe that they hide a thus-far unknown, compact and very transient phase of growth. It is either an accreting supermassive black hole, or an extreme form of star birth. The hidden activity also drives huge ‘winds’ and ‘jets’ which eventually expels gas and dust from the galaxy's core. It may be that these winds act as a control system for the evolution of the galaxies.”

Investigating things that are hidden sounds quite difficult. How are you doing it?
“We need to use long-wavelength radio waves, invisible to the human eye, that can pass through the dust and gas and reveal the hidden activity. We have developed a method where we use radiation from molecules, and astrochemistry as ‘measuring tools. We use large international telescopes such as ALMA, the Atacama Large Millimeter Array, in Chile – where Chalmers is also an important supplier of internationally leading receiver technology (Read more: Receivers from Chalmers will image the distant universe​). Chalmers is also involved in even more long-wave technology, participating in international networks of interconnected telescopes, such as LOFAR and VLBI, and in the future, SKA.”

What are you hoping the project will lead to?
"We hope, among other things, to find a key to the puzzle of how supermassive black holes grow together with ‘their’ host galaxies, and to see what mechanisms drive the development of the universe forward. We are also looking for evidence that supermassive black holes can regulate their own growth. This can take place through the winds, for example. If they are powerful enough, they can propel gas from the galaxy completely. If they are weaker, the gas flows back so that it can contribute to further growth.”

Your colleague, Professor Jonathan Tan at the Division of Astronomy and Plasma Physics, has also been awarded an ERC Advanced Grant this year (Read more about Jonathan's project Massive Star Formation Through the Universe​). Your division is part of the Department of Space, Earth and Environment. What does it mean for Chalmers to have two such big allocations in the field of astronomical research?
"The ERC awards give us the resources that make it possible to work on large scale research questions. This means that Chalmers can consolidate its place in the world’s elite in mm, submm and radio astronomy. At Astronomy and Plasma Physics we work closely with Onsala Space Observatory and this cooperation is important to our success. We are also looking forward to broadening our cooperation with other institutions, as well as other departments and institutions at Chalmers.”

How do you plan to spend the ERC grant funds? 
"In order to address these questions, we need a coordinated observation program on several international telescopes. There is the existing facility at ALMA (link), and two new telescopes scheduled to start in 2020: the James Webb Space Telescope, which will observe space from orbit, and the SKA, or Square Kilometer Array, which will become the world's largest radio telescope.
In addition, we need t  further develop our modeling work on for example radiative transport, dynamics, astrochemistry and MHD simulations of jets. So we plan to use the money to build a research team.”

You are the only woman at Chalmers with an ERC Advanced Grant. What are your thoughts about that?
"Looking at the ERC statistics for advanced grants, Sweden is not doing so well in terms of gender equality. It is interesting to ask why this is, and what we can do about it. In general, it looks much better for starting grants than for advanced. Is this a sign that we can look forward to a new era of more prominent female researchers? Or is it a confirmation of a gloomier picture, where fewer women make it at the ‘higher’ levels? The balance has improved slightly within astronomy at Chalmers. As a researcher and head of department, I want to contribute to an environment where people are seen as individuals, and can develop, and also where women do not ‘fall away’ from research to a greater degree than men", says Susanne Aalto. 

Text: Christian Löwhagen. 

Published: Thu 05 Apr 2018. Modified: Wed 11 Apr 2018