Astronomy Centre

Jon Loveday

A cosmic census of star formation over the last five billion years

Collaborators: Galaxy and Mass Assembly (GAMA) team (Europe, Australia)

Funding: STFC quota studentship.

Understanding where and when stars form in galaxies is one of the key challenges in extragalactic astronomy.  In this project, you will use data from the Galaxy and Mass Assembly survey (GAMA)  to investigate the dependence of star formation rate on properties of the host galaxies, such as stellar mass, and on environment, as defined by galaxy density and halo mass, and its dependence on redshift over the last third of the age of the Universe. These observations will be used to constrain models of galaxy formation and evolution by comparing with their predictions, thus helping us to understand how the galaxies we see today came to be.  In particular, you will address the following questions:

  •  How does overall star formation rate (SFR) evolve with redshift?
  •  Where is star formation taking place as a function of redshift?
     - In what mass galaxies?
     - In what environments?
     - What is most important in determining SFR, intrinsic galaxy properties or environment, and does this change with redshift?
  • What is the link between star formation and AGN activity? Do AGN activity and SFR drop off at the same rate in massive galaxies?


The GAMA survey provides a valuable resource with which to study in detail the evolution of star formation, including its dependence on intrinsic galaxy properties such as stellar mass as well as environment, since redshift z ~ 0.5, covering a lookback time of 5 Gyr, about one third of the age of the Universe.  GAMA phase 1, completed in 2010, includes more than 100,000 galaxies with spectra and reliable redshifts within three 12 x 4 degree fields to r band magnitude limits of r = 19.4 (two fields) or r = 19.8 (third field).   GAMA phase 2, running from 2010-2014, is extending survey coverage to two additional fields and a uniform depth of r = 19.8, ~375,000 galaxies.   As a GAMA executive team member, Jon Loveday and his students have access to all GAMA data products before they are made publicly available.

Project outline:

Year 1: Directly determine SFR in bins of stellar mass, halo mass, local density and redshift within volume-limited samples.

Year 2: Determine joint multivariate distribution of above properties, correcting for galaxies missed due to low surface brightness.

Year 3: Determine the dependence of galaxy clustering on intrinsic properties, both by subdividing the sample on stellar mass and SFR, and by using marked correlation functions, providing . a detailed picture of the scale out to which environment influences intrinsic galaxy properties.  Write papers and thesis. Present work at international conference.

The student will be expected to visit collaborators within the UK and Europe and to assist with spectroscopic observing and redshifting at the Anglo Australian Telescope at all stages of their DPhil.

For more information/to apply for this project, please contact J.Loveday[AT]sussex.ac.uk.