Why Are Mergers Important?

What will we use our merger data for?

Mergers are really interesting since they are the main process by which the universe evolves its galaxy population and creates more and more massive galaxies. Additionally, the collision between two galaxies involves ALOT of energy. This energy gets transferred into compressive forces when clouds of gas in the galaxies collide and collapse into violent bursts of star formation. Understanding how all the stars in the universe form is a really important aspect of a full understanding of the cosmos and so mergers help us understand some of the key observations made in modern astronomy. We also want to know what fractions of mergers involve spirals and how many are ellipticals, what is the typical mass ratio between merging galaxies and whether or not mergers tend to happen in clusters or not.

The Merging Anntennae Galaxies

Another important contribution mergers can make is help us understand the formation of Active Galactic Nuclei (AGN). Mergers and, more generally, galaxies with disturbed morphologies often turn out to be Ultra-Luminous-Infra-Red Galaxies (ULIRGs) which are themselves interesting because they tend to host AGNs. An AGN is thought to be a Super Massive Black Hole that sits at the centre of a galaxy and produces vast quantities of radiation as matter falls into it (this is called ‘accretion onto a black hole’). AGNs produce vast amounts of light that far out strips that emitted by all the stars in its galaxy combined. Also, they sometimes produce dramatic jets of matter that fly out at relativistic speeds. Alot is still unknown about the mechanism that produces these jets and so AGN and their formation is a hot-topic of research. Distant quasar galaxies are thought to be AGN and tell us much about the formation of the first galaxies in the universe. The more we know about AGN and how they form, the more we can know about some of the distant events near the beginning of the universe. Specific properties of AGN can be probed by examining the spectra that they produce and we hope to apply these tests to all of the good mergers that we find.

AGN Illustration

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4 responses to “Why Are Mergers Important?”

  1. jokergirl says :

    I have one problem with the merger identification on the site (been doing the merger analysis for the last few days now): It is much easier to classify a spiral-on-spiral or spiral-on-elliptical merger than an elliptical-on-elliptical. I believe the classification will bring up a much higher percentage of spiral mergers than ellipticals even with the additional classification help.


  2. Daniel says :

    Thanks for your comment jokergirl…

    Yes, this is a concern of ours too and we will be sure to examine whether the fraction of spiral-spiral to elliptical-elliptical (and spiral-elliptical) changes with vote-category. If you are right, we’ll find a higher fraction of s-s mergers in, say, the 80-100% voting category compared with the 60-80% and 40-60%. If there is a user-bias of this nature, we will be able to spot it and we’ll do some statistics to correct for it!

    Thanks to everyone for your continued involvement!

  3. lion2007 says :

    very very nice.thanks

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