Analysing the next generation of galaxy surveys

Lead Research Organisation: University of Portsmouth
Department Name: Institute of Cosmology and Gravitation

Abstract

The Earth, the Sun and the nearby stars that can be seen in the night sky form part of the Milky Way galaxy. The Milky Way galaxy is just one of the many billions of galaxies in the Universe. These galaxies have many different types and sizes, and are not distributed randomly, but instead cluster in a complex pattern. For example, if you know that there is a galaxy in a particular location, you are more likely to find another galaxy close by than if you picked a different location chosen at random. Although astronomers have observed many different types of galaxy, we do not yet have a complete model for the formation and evolution of these galaxies. Galaxies can change type by forming new stars, old stars can die, and galaxies can merge together. In general, if we observe two types of galaxy then we cannot say that one will turn into the other, or whether they are completely unrelated. Galaxy evolution takes place extremely slowly compared with the human lifespan, so we cannot simply wait and see what happens! A primary goal of modern astronomy is to understand the physics of galaxy formation by providing computer simulations of galaxy populations with properties that match those of observed galaxies. At the moment, many models have been proposed and we cannot tell which is closest tot he behaviour of our Universe. One of the ways to rule out particular models is to collect more data about the Universe in which we live, and the pattern of galaxies of different types and brightness provides a lot of information. I will analyse maps of the positions of many thousands of galaxies observed using large telescopes in order to provide the required information and solve this problem. In addition to learning how and why galaxies form, astronomers can also use the large-scale distribution of galaxies to learn about the physical properties of the Universe. There are two important problems in modern physics that I wish to solve. First, I wish to measure the masses of Neutrinos in the Universe. Neutrinos are particles that only very weakly interact with ordinary matter and are very difficult to observe directly. However, the value of their mass is imprinted on large-scales in maps of galaxy positions. I will therefore be able to learn about Neutrinos by analysing the Universe on very large-scales; an amazing link between the incredibly small- and large-scales considered in modern physics. Secondly, the distribution of galaxies has the potential to tell us about the behaviour of the vacuum - the space between galaxies. It is now thought that the vacuum behaves in a strange way causing the expansion of the Universe to accelerate. I will lead a project to understand the behaviour of the vacuum using the observed galaxy distribution. Because of the importance of maps of the distribution of galaxies, there are many different surveys of galaxies underway and planned that I intend to analyse. Some of these surveys will measure the distance to each galaxy in a new way. Instead of providing accurate distances to the galaxies leading to a 3-dimensional map, some new surveys will instead simply tell us how likely a range of galaxy distances are. At the moment, survey analysis methods cannot use such information. Techniques have previously been developed when there is no information, or when galaxy distances are accurately known, but not for the intermediate case. The work that I am proposing will develop the required techniques and use these techniques to analyse maps in order to set constraints on allowed models of galaxies. One survey for which I am leading the analysis of the distribution of galaxies, aims to map a set of extremely bright galaxies in the distant Universe (this survey is called the SHADE survey). The energetic galaxies within this survey are far brighter than the Milky Way, and are likely to form one of the key stages in the evolution of galaxies. By analysing the distribution of these galaxie

Publications


10 25 50
Abazajian K (2009) THE SEVENTH DATA RELEASE OF THE SLOAN DIGITAL SKY SURVEY in The Astrophysical Journal Supplement Series
Coppin K (2006) The SCUBA Half-Degree Extragalactic Survey - II. Submillimetre maps, catalogue and number counts in Monthly Notices of the Royal Astronomical Society
Cresswell J (2009) Scale-dependent galaxy bias in the Sloan Digital Sky Survey as a function of luminosity and colour in Monthly Notices of the Royal Astronomical Society
Nock K (2010) The effect of redshift-space distortions on projected two-point clustering measurements in Monthly Notices of the Royal Astronomical Society
Percival W (2007) Measuring the Matter Density Using Baryon Oscillations in the SDSS in The Astrophysical Journal
Percival W (2008) Galaxy peculiar velocities and evolution-bias in Monthly Notices of the Royal Astronomical Society: Letters
Percival W (2005) Cosmological structure formation in a homogeneous dark energy background in Astronomy and Astrophysics
 
Description Lots of science, with the main work being analyses of Baryon Acoustic Oscillations in SDSS-II data.
Exploitation Route Led to BAO science becoming one of the pillars of modern observational cosmology.
Sectors Education
 
Description ERC starting Researcher Grant
Amount £660,000 (GBP)
Organisation European Commission (EC) 
Sector Public
Country European Union (EU)
Start 10/2008 
End 10/2013
 
Description Philip Leverhulme Prize
Amount £70,000 (GBP)
Organisation The Leverhulme Trust 
Sector Academic/University
Country United Kingdom of Great Britain & Northern Ireland (UK)
Start 10/2008 
End 10/2011
 
Description Astronomy Society Talk 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Primary Audience Public/other audiences
Results and Impact Approximately 2/year talks to astronomy societies. Audience ~20 (mainly retired engineers)

Good feedback was received by email from some groups
Year(s) Of Engagement Activity 2006,2007,2008,2009,2010