Galactic archaeology

Unravelling the formation and evolution of galaxies is an active area of astrophysical research. How does the structure form, and what processes are most important in shaping galaxies as we see them today?

Overview

One way to address this is to forensically analyse nearby galaxies, and determine how they have formed over the age of the Universe. This field is often referred to as ‘galactic archaeology’. Rather than trowels and brushes, our tools are large telescopes, and detailed numerical simulations. And the fossils we study are the individual stars within a given galaxy.

As we need to study the properties of individual stars to build up a galaxies formative history, we are limited in which objects we can study, they need to be near enough that we can take images and spectra of their stellar populations. Fortunately, our own local group provides tens of galaxies for which this data can be obtained. Here at Surrey, we are actively involved in a number of large scale surveys of nearby galaxies to address how they are formed.

Resolved stellar populations in nearby galaxies

Group member Dr Noelia Noel’s, leads a team who work extensively with data concerning the two largest satellite galaxies of the Milky Way: The Large and Small Magellanic Clouds. This pair of galaxies are interacting not only with our Galaxy, but also with each other. By studying these interactions, and the stars within the Magellanic Clouds, we can determine their role in shaping our Galaxy today, and learn about their cosmic evolution.

Here at Surrey, we are involved in a large scale survey of these systems, known as SMASH (the Survey of the MAgellanic Stellar History Survey). This survey uses the Dark Energy Camera, located on the 4m Blanco Telescope in Chile.

Deciphering the evolution of the Andromeda Galaxy

Another member of our group, Dr Michelle Collins, is a lecturer here at Surrey whose team works on deciphering the evolution of our nearest spiral neighbor: The Andromeda Galaxy. Dr Collins is part of the Pan-Andromeda Archaeological Survey (PAndAS), which has imaged this system out to half its virial radius. The resulting image shows spectacular evidence for a galaxy that has grown as the result of multiple mergers with smaller galaxies. Dr Collins leads the spectroscopic follow-up of dwarf galaxies orbiting Andromeda, determining their dark matter content. Additionally, the team makes extensive use of data from the Gaia telescope to study our own Galaxy in detail.

Mapping stellar streams

Group member Dr Denis Erkal has been mapping stellar streams throughout the stellar halo of the Milky Way, and determining the influence of the Large Magellanic Cloud on the shape of our Galaxy.

Further research

Members of our group also use the 8m Very Large Telescope in Chile for follow-up, and have begun a new survey of nearby dwarf galaxies using the 4m William Herschel Telescope in the Canary Islands.

In order to interpret these vast datasets, our group also compare data with simulations. Many of these simulations come from our Surrey astrophysicists, with expertise from both Professor Justin Read and Dr Denis Erkal.