New Radio telescopes like the MeerKAT and the future SKA are opening up a new window of 21 cm emission by atomic hydrogen gas, the fuel of the Universe. This new perspective on the Universe allows us to explore topics of spiral disk evolution,
for example, the interaction and merger of spiral galaxies. Mergers are thought to be the main mechanism driving evolution of spirals to ellipticals. But how important? When did most of these mergers take place? There are many ways to estimate the number of mergers but here I focus on how galaxies look (morphology)
Morphology of spirals can be quantified using specific parameters: concentration (C), asymmetry (A), smoothness (S), second-order-moment (M20), the GINI coefficient (G), and a mix between the last two (GM). Within these parameters, we can identify different Hubble types in optical images. Some of them are sensitive to when a merger happens as the galaxies start to look disturbed. In this project I had a look how well these parameters work on radio images of atomic hydrogen.
Combined with an estimate how long a galaxy looks disturbed, we can now measure how many galaxies are merging in a given volume of the Universe from how they look in HI radio maps. The new surveys with MeerKAT and its Australian counterpart ASKAP, will immediately give us a better idea how often mergers happen in the local Universe. In the SKA era, this can be extended to the earlier Universe.