Galaxy And Matter Assembly

Approximately 15 billion years ago, and only ~300,000 years after the Big Bang, we can see the distribution of baryons (the stuff you and I are made of). It is extremely smooth to one part in ~100,000 and comprised mainly of neutral hydrogen, deuterium, helium and lithium with some miniscule quantities of heavier elements (what astronomers call metals). Today we see that the nearby universe is comprised of galaxies - isolated systems of stars, gas, dust and plasma - distributed in a filamentary structure. The filaments contain low density plasma which is slowly infalling into the galaxies dotted along the filaments. The intersections of the filaments constitute giant complex clusters of galaxies. Between the filaments are the voids. The Universe that we see today and the one we see 15 billion years ago in the past are dramatically different. Somehow the baryons in the Universe have reordered themselves from the very smooth distribution we see today. In terms of metals (those atoms you and I are made of) the only locations in which these can be made are in the cores and supernova shells which reside in galaxies, the engines by which collapsing and infalling hydrogen gas is processed (via stars and stellar nucleosynthesis) to produce the metals, dust and stellar relics that ultimately give rise to solar systems, planets and life. In this project we aim to conduct a definitive census of the nearby universe focussing on the baryons and where they reside today. What fraction are in galaxies and what fraction lie in the inter-galactic medium? Within galaxies what fraction of the baryons are in the form of supermassive black holes, young stars, old stars, planets, dust, gas or plasma? How are the stars distributed and what fraction are in bulges, pseudo-bulges, disks or non-equilibrium structures? How are the density and distribution of the stars, gas and dust correlated? The past ten years has seen a revolution in our understanding of the large scale distribution of galaxies and matter. Here we will take the next logical step of exploring galaxy diversity and to comprehensively define what is a galaxy, what types of galaxies exist, how many of each type and how their stars are distributed.