ICREA Research Professor @ICE-CSIC
I study dust properties in order to understand the formation of dust in galaxies. In particular, I use far-infrared and submillimeter observations of evolved stars and the interstellar medium of nearby galaxies to study the dust emissivity properties at these wavelengths, with the goal to improve dust mass determinations at all redshifts. I also determine the mineralogical properties of silicate dust -- crystallinity, composition, nanocluster fraction -- in interstellar environments to follow dust formation and evolution.
Interstellar dust masses
Calibrating dust mass determinations is important because many galaxies are only or predominantly observed in the submillimeter, and their molecular gas masses and star formation rates are derived from the dust masses inferred from far-infrared and submillimeter photometry. Thus, gaining an understanding in the accuracy of dust mass determinations has consequences for our view of galaxy evolution.
AGN dust formation
The wind lifting off from the accretion disks around AGB stars may provide the conditions required to form dust. It has been hypothesized that this freshly formed dust contributes and actually composes the conveyor belt of dust that gives rise to the dusty torus. We have identified the composition of the dust in the accretion disk wind and found that it deviates significantly from the interstellar dust composition in the Milky Way. The James Webb Space Telescope will observe many AGN insufficient detail to continue this analysis.
Silicate dust destruction leads to the formation of SiO molecules, a processed which has been observed in the interstellar medium. The coagulation of such SiO molecules, along with Mg and Fe cations, into silicate nanoclusters is still to be observed. Silicate nanoclusters are an intermediate step in the formation of interstellar silicates. Quantumchemical calculations can predict the spectral appearance of nanoclusters. We are currently searching for the corresponding spectral signature in the interstellar medium, in the mid-infrared and the millimeter-wave regime.
Crystalline silicates in the ISM of galaxies
Observational evidence has long supported that most of the interstellar silicates in galaxies are amorphous. While crystalline silicates may form around evolved stars at temperatures sufficiently high to allow for annealing, it is thought that the harsh interstellar environment quickly amorphitizes any crystalline silicates, most likely through bombardment by the heavy ions in cosmic rays, and a firm upper limit of 2% on the crystalline fraction of silicates was derived based. We are characterizing silicates in circumstellar and interstellar environments and modelling the cycle of crystallization and amorphization.
Facilities and Instrumentation
I have been involved in collaborative instrumentation projects, especially related to the Atacama Large Millimetre/Submillimetre Array (ALMA). While at ASIAA in Taiwan, I was the Principal Investigator of the Band 1 Receiver Development project, and co-project manager of the total package of ALMA activities in Taiwan. At ESO in Germany, I took up the role of the European ALMA Programme Scientist. In this role, I provided scientific justification for the ALMA 2030 Development program, and liaised with the science advisory committees. I have also been involved in the James Clerk Maxwell Telescope (JCMT) as the East Asian Observatory chief scientist. Currently, I am a science team member of the AtLAST consortium, a member of the SKA science working groups and a member of the science team of the African Millimetre Telescope (AMT), which is part of the Event Horizon Telescope (EHT). On the infrared side my expertise dates back to my Ph.D. project, where I was embedded in the Dutch/Belgian ISO-SWS community, and later my position as Spitzer Fellow, which allowed me to join the IRS instrument team. I have also been a very active member of the science team for the Space Infrared Telescope for Cosmology and Astrophysics (SPICA), which would have been the next far-infrared space-based observatory had it not been cancelled. I have been instrumental in establishing the participation of ASIAA/Taiwan in the METIS instrument for ESO’s Extremely Large Telescope.
Other science interests
Observational evidence of evolving exoplanetary systems
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