3rd Blog Post: Visual Classification of Galaxies

This week, I have been analysing data about the type of environment in which galactic mergers happen. I have combined my results and the results of Galaxy Zoo with data about the density of galaxies in the superstructure to see whether mergers are more common in denser or less dense regions.

This animation shows the numbers of mergers at each value of ‘logdelta’ for ten intervals of 0.01 redshift between redshifts of 0.8 and 0.9.

The higher the redshift, the further back in time we look, so in a way this animation shows a progression backwards in time of the superstructure. Each of the bands at the bottom of the image represents a different ‘density bin’- the blue colour scheme shows low density, the pink colour scheme shows intermediate density and the green/blue colour scheme shows high density.

As is visible, there is a general trend towards mergers in intermediate density environments further back in time and in higher density environments further forward in time. This could be because as galaxies merge and interact there are more galaxies in a higher density environment and so more mergers happen there.

This animation shows the physical locations of the mergers that I classified going from redshift 0.8 to redshift 0.9 with the density of galaxies. The red stars represent mergers.

The above animation seems to show that the mergers usually occur in higher density areas and can be seen to ‘track’ the high-density areas as they move around. Similarly to the graph, this shows that the mergers I classified occur in intermediate to high-density areas. This would make sense given that mergers require galaxies to be near each other to occur.

This animation is similar to the previous animation, but shows galaxies that more than 50% of people said were merging and covers many more galaxies than I classified.

Again, it can be seen that the mergers roughly follow the high-density areas as the redshift changes. It is possible that this trend would be more marked if only galaxies with a higher percentage of the vote for being a merger were used, but I have not yet tested this hypothesis.

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