Supermassive Black-Holes in Formation and their Role in Galaxy Evolution

Lead Research Organisation: University of Cambridge
Department Name: Institute of Astronomy


Our Universe contains billions of galaxies like our own Milky Way, each harbouring a supermassive black-hole at its centre. The biggest galaxies today weigh more than a trillion times the mass of our Sun with supermassive black-holes weighing the equivalent of a billion Suns. But how did these galaxies and black-holes get so big? The Universe is almost 14 billion years old but the major growth spurt of galaxies took place more than ten billion years ago. Theory predicts that this epoch in our Universe's history was characterized by violent collisions of small galaxies. These collisions compressed the gas in galaxies to form stars, the new stars provided fuel for the supermassive black-holes to feed on and the massive galaxies of today were assembled with enormous black-holes at their centres.

Despite this well-accepted picture of galaxy formation we still have not observed many of these processes happening, particularly during the very active period of growth in our Universe's history more than 10 billion years ago. We want to catch the most massive galaxies and supermassive black-holes as they are growing but these systems are very rare; looking for them is comparable to looking for a needle in a haystack! Not only do we need sophisticated telescopes that can scan the entire sky searching for these monster galaxies, they also need to be sensitive enough to detect light that has traveled billions of years from when the galaxies were first forming, to reach us today. This has only recently become possible and new digital cameras have been mounted on some of the largest telescopes in the world to provide sensitive images covering most of the sky. I am working on data from several of these new digital imaging surveys.

My research involves scanning the digital images to locate the most enormous galaxies in our Universe as they are undergoing a major growth spurt. I have already identified the first of these ultra-massive growing galaxies in the distant Universe. Through high-resolution imaging of these newly discovered galaxies, we will be able to observe the various physical processes going on within them and how the supermassive black-hole is affecting these processes.

Within our new digital images of the sky lurk even rarer systems such as the first galaxies and supermassive black-holes in our Universe dating back to when the Universe was only 500 million years old. We are now able to watch these galaxies as they begin to feed their supermassive black-hole for the first time on their journey to growing to the monster black-holes of today. Observing this first feeding phase is critical for building up an understanding of how supermassive black-holes grow.

Most digital imaging surveys detect starlight from galaxies in the visible portion of the electromagnetic spectrum. However, dust in galaxies can absorb visible light, which is then re-radiated at the longer infrared wavelengths. Infrared data therefore allows the most unbiased view of star formation in galaxies. Utilising new surveys that trace light at infrared wavelengths, my research will measure the number of stars being formed in distant galaxies with actively feeding supermassive black holes. The aim is to determine if the supermassive black-hole directly impacts the rate at which a galaxy is forming stars, therefore controlling how massive its host galaxy will eventually become.

Taken together my research aims to build up a coherent observational picture of the formation of massive galaxies and supermassive black-holes by directly observing them as they are being assembled in the early Universe. This will be done by bringing together new data from some of the largest astronomical surveys across the electromagnetic spectrum, that are currently underway.
Description AAO 
Organisation Australian Astronomical Observatory
Country Australia 
Sector Public 
PI Contribution I am a member of the OzDES survey being conducted at the Australian Astronomical Observatory and have contributed to both quasar and galaxies science as part of this project.
Collaborator Contribution As a member of the survey, myself and my students get preferential access to proprietary data from the survey for research purposes.
Impact Several research papers have resulted from my involvement in the OzDES survey, details of which can be found in the Publications section of this submission.
Start Year 2012
Description DES 
Organisation Dark Energy Survey (DES)
Country Global 
Sector Charity/Non Profit 
PI Contribution I am a Science Committee member within the Dark Energy Survey collaboration. I co-lead the the Galaxy Evolution and QSO Science Working Group. I have "Builder" status within DES, which recognizes >2 years of infrastructure work within the collaboration.
Collaborator Contribution As a member of the DES Collaboration myself and my students have preferential access to proprietary data from the survey, which is being used for my research.
Impact I have authored or been co-author on a number of scientific publications as part of the DES Collaboration. All relevant publications are listed in the Publications section of this submission.
Start Year 2008
Description LSST 
Organisation LSST Corporation
Country United States 
Sector Charity/Non Profit 
PI Contribution I have recently joined the LSST project through the Galaxies and Dark Energy Science Collaborations. I am also a member of the Science Working Group for LSST:UK, within which I am the Infrared Liaison and I co-ordinate multi-wavelength data fusion efforts.
Collaborator Contribution In collaboration with other members of LSST, we are putting together a Scientific Roadmap for LSST Galaxies science.
Impact Scientific Roadmap for LSST Galaxies science in preparation.
Start Year 2016
Description VISTA 
Organisation VISTA
PI Contribution I am a member of several public surveys being undertaken with the ESO VISTA telescope including the VISTA Hemisphere Survey, VIKING and VIDEO. I lead the new VISTA VEILS survey recently approved as an ESO VISTA Public Survey starting in 2017. I am also a member of the VISTA-4MOST project due to begin scientific operations in the 2020s and am on the Infrastructure Coordination Board for that project.
Collaborator Contribution As a member of these surveys, myself and my students get early access to proprietary data from the surveys for my research purposes.
Impact N/A
Start Year 2009