• Research in astrophysics
• PhD thesis

Research in astrophysics

The galaxy NGC 4449

False-colour SDSS image of NGC 4449.

In my previous research in astrophysics I studied nearby galaxies. In particular, I focused on unevolved galaxies, which means those smaller in size, lower in mass and lacking heavy elements. They are referred to as low-metallicity dwarf galaxies. NGC 4449, situated at a distance of 3.8 Mpc (12.4 million light-years), is one of the most studied low-metallicity dwarf irregular galaxies with an exceptional coverage of multiwavelength observations.

Observations of these galaxies give us an insight into the physical and chemical conditions in the first generations of galaxies formed in the Universe. My work focused on understanding their physical and chemical composition, their star formation histories and the evolutionary processes determining the properties of their interstellar medium.

Measuring dust masses in supernova ejecta

Interstellar dust takes the form of small particles spread throughout space in galaxies. Dust is believed to form around evolved stars and in the material ejected from massive stars in supernova explosions.

Before and after Spitzer/IRAC images of NGC 1058 showing the supernova SN 2007gr.

The physical and chemical properties of dust encode the past star formation activity and, by regulating the local heating and cooling processes of gas, also determine the properties of the stars that may be formed in the future.

Improving treatment of Swift/UVOT images of extended sources

The isophotal setup applied to NGC 4449.

In the course of my PhD I also developed a strategy to make a non-standard use of images taken with the Swift Ultraviolet/Optical Telescope (UVOT), which was built by UCL’s Mullard Space Science Laboratory.

In Swift/UVOT each ultraviolet/optical photon that enters the telescope is electronically multiplied to produce a splash of photons on the detector. While this engineering solution allows for sub-pixel accuracy of the incoming signal, it is at the same time very sensitive to saturation effects, where positional information can be lost due to too many photons arriving at a similar location on the detector within one readout cycle. In my PhD I presented a method that can handle images that suffer from this pile-up effect.