Data: 26.11.2024

William Pearson (NCBJ,PL)

Galaxy mergers: where, and what, are they?

Streszczenie:
Galaxy mergers underpin our current understanding of how galaxies grow and evolve over cosmic time. In our current dark matter cosmology, the dark matter halos grow hierarchically. As a result, the baryonic component that the halos host, the galaxies, also collide. These mergers can radically change the morphologies of the interacting galaxies, throwing dust, gas and stars around and creating and destroying fainter and finer structures. The merging galaxies can also undergo massively increased star-formation rates or highly enhanced active galactic nuclei activity. But when these powerful events occur, and indeed how powerful they can be, is hotly contested. Thus we need large, statistical samples to better understand what happens.

Identifying galaxies is not as simple as it first appears. Visually checking images is the most obvious method but it is flawed. The most advanced machine learning methods overcome some of these flaws but are not without their own issues. During this seminar we will discuss a range of different techniques that we use to identify galaxy mergers, comparing their strengths and weaknesses. We will get the opportunity to see how some advanced techniques can reduce the galaxy merger identification to a much simpler, yet surprising, problem. We will also explore how we can go beyond a simple binary classification, of merger or not, to something much more refined.

This all assumes that we know what a galaxy merger is. Surprisingly, as we will find out, this is not as obvious as it first appears. So we will also discuss how we can understand exactly what a galaxy merger is