Science

 

This is a brief (and somewhat outdated/incomplete, update in progress) summary of what I work on. If you want to know more, please check my publication list and/or ask me about it.

[Or you can invite me to give a talk at your department and we can chat about my work extensively and in detail ;-) ]

 

My general research interests include galaxy evolution, in more detail: the transformation from disk galaxies into ellipticals and the influence of environment on galaxy parameters such as shape and colour gradients. I am best known for my more technical work on fitting galaxy profiles, though, that I have carried out throughout my career (with gaps). I was involved in developing a new, multi-wavelength method to do this, please check here for details.

 

Survey and Collaboration Memberships
(selection)

 

 

 

Galaxy Profile Fitting
(GEMS, STAGES, MegaMorph, GAMA, VIDEO)

 

Profile fitting is an important and powerful tool to study galaxy parameters and galaxy evolution. I have written and tested software to do this which was used for work on magnitude-size relations (Barden et al., 2005) and quite a few others by now

See publications here (GEMS) and here (STAGES, chapter 2.4-2.5).

 

For the most advance of these works, our new multi-wavelength tool, developed by the MegaMorph project, please see here.

 

Blue Ellipticals
(GEMS)

 

Blue Spheroids/Ellipticals are a vital stage in the life of elliptical galaxies. A recent merger transformed a galaxy into an elliptical shape, but young, blue stars still exist. Using the largest sample of such galaxies in existence (from GEMS) and deeper data (e.g. UDF), most of the blue ellipticals indeed show faint signs of recent merger events and, by comparing their numbers to the numbers of mergers, we show that they indeed seem to form this transition population. 

See chapter 4 in my thesis.

 

Galaxy Colour Gradients
(GEMS, CANDELS, MegaMorph)

 

Colour gradients in galaxies can give important clues about the assembly history of the galaxy. 

I have looked at galaxy colour gradients in GEMS, but the data wasn’t good enough, unfortunately.

With MegaMorph, for the first time, a tool exists that allows the measurement of colour gradients in an automated, fully understood fashion on large sample of galaxies (Kennedy et al, in prep). 

 

Image from DSS

Testing detection completeness
(GEMS, STAGES)

 

I used and use image simulations to test the detection completeness (and fitting reliability) as a function of galaxy shape, brightness and size. This helps to understand observational biases within our surveys.

 

See here (GEMS) and here (STAGES, chapter 2.5).

 

Galaxy 'Classifications'
(e.g. CANDELS, Galaxy Zoo) 

 

Robust galaxy classifications are vital when trying to separate galaxy populations (e.g. disks vs ellipticals). Galaxy Zoo provides a great setup to get these classifications. Already having classified both local (SDSS in Galaxy Zoo 1&2) and more distant data (GEMS, AEGIS, COSMOS, GOODS in Galaxy Zoo: Hubble), CANDELS data is a natural next step for classifications. IR-data shows galaxies at higher redshifts, thus creating a huge & uniformly classified sample of galaxies at all redshifts.

I can't wait to get my hands on the classifications in order to work with CANDELS data, especially in combination with MegaMorph.

 

Image from GalaxyZoo

Last updated September 2020