Research

PhD: DLAs and the relation to Lyman-break galaxies

In my PhD (1996–2000, with Palle Møller and Bjarne Thomsen) I worked on Damped Lyα Absorbers (DLAs) as high-z galaxies selected via absorption in QSO spectra. Absorption selection provides an alternative and complementary view of the galaxy population and its chemical enrichment.

The thesis is available here: thesis.ps.gz. Two central outcomes on the original page were: (1) DLAs must belong to a much more numerous, typically fainter galaxy population than the then-known Lyman-break galaxies; (2) an early example of what later became known as “Lyα blobs”.

Broadening the selection: absorption, emission, and transients

After the PhD I worked as a fellow at ESO and continued collaborating with Palle Møller. From ~2000–2010 the focus broadened to galaxies selected in other ways than absorption: GRBs and their host galaxies, and Lyα emitters.

The guiding idea is to combine multiple selection techniques (absorption, emission, dust bias, multi-wavelength data) into a consistent picture of galaxy formation.

Dusty DLAs via searches for red quasars

From around 2010, dust in DLAs and GRB hosts became a main focus. One key activity has been to identify dusty and metal-rich DLAs via searches for red quasars, leading to multiple ongoing projects.

Gaia: purely astrometric quasar selection

Together with Erik Høg and Kasper Heintz, I started work on using Gaia astrometry to build a more unbiased quasar sample. This has resulted in a method description and pilot results.

• A&A (2015): purely astrometric selection
• A&A (2018): unidentified quasars in Gaia DR2
• A&A (2020): spectroscopic classification of astrometric candidates