The cycle of life, death and rebirth in massive early-type galaxies; star formation, black-holes and feedback

Lead Research Organisation: Cardiff University
Department Name: School of Physics and Astronomy

Abstract

My research focuses on understanding the biggest galaxies that exist around us in the local universe. These objects are interesting because they are thought to be the end point of galaxy evolution. They are made up of billions of old stars, have red optical colours, and are generally thought to be free of cold gas - the fuel for new stars. Thus they are often described as "red and dead". Astronomers still don't fully know what caused these galaxies to die off, or if they can come back to life again. It is these processes that I am investigating.

One of the ways astronomers think these massive galaxies become "red and dead" is due to the supermassive black-holes that lie at their cores. These enigmatic objects are clearly linked to galaxy formation, as they seem to grow in step with their galaxy host. In order to understand the role of black holes in the formation of galaxies, I developed a new technique to measure their masses, by tracing the motions of molecular gas clouds swirling around them. This technique is exciting, because it opens up the possibility of measuring black hole masses more accurately, and in more galaxies than ever before. As part of my Rutherford fellowship I aim to use this technique to reveal the dark monsters lurking at the hearts of nearby galaxies.

When black holes swallow matter they emit large amounts of high energy light, and can accelerate large jets of particles. Both of these processes can affect gas clouds, throwing them out of galaxies. These outflows are one mechanism that can help form the gas-poor massive galaxies I study. A few years ago I helped identify one of the nearest examples of a black hole expelling large amounts of gas in this way. During my Rutherford fellowship I will use the chemistry of the gas in this outflow to determine whether it is the extremely strong light from the black hole, or the jet of particles that is causing the outflow we see. This will give us one more piece of the puzzle, helping to explain why most massive galaxies with big black holes are gas poor.

Massive galaxies, like the ones I study, don't have to stay "red and dead". The can come back to life if material from dying stars can cool and become fuel for a new generation of stars. They can also merge with other small galaxies and steal their fuel. Around 1/4 of the massive "red and dead" galaxies around us today are currently in the process of being reborn. Understanding which process causes this, and what effect surrounding galaxies have, will allow us to determine whether these galaxies are destined to fail and go back to being "red and dead", or if they can eventually come back to life fully.

I have discovered that these objects that have obtained fuel for star-formation, don't seem to be using it very effectively. They are very inefficient at forming stars when compared to galaxies like our own Milky Way. I aim to find out why this is happening, and what this can tell us about the physics controlling star formation in the universe.

Publications

10 25 50
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Agius N (2015) H-ATLAS/GAMA and HeViCS - dusty early-type galaxies in different environments in Monthly Notices of the Royal Astronomical Society

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Alatalo K (2015) Evidence of boosted 13CO/12CO ratio in early-type galaxies in dense environments in Monthly Notices of the Royal Astronomical Society

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Davis T (2019) Gas accretion as fuel for residual star formation in Galaxy Zoo elliptical galaxies in Monthly Notices of the Royal Astronomical Society: Letters

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Davis T (2016) On the depletion and accretion time-scales of cold gas in local early-type galaxies in Monthly Notices of the Royal Astronomical Society

Related Projects

Project Reference Relationship Related To Start End Award Value
ST/L004496/1 01/10/2014 30/09/2015 £394,480
ST/L004496/2 Transfer ST/L004496/1 01/10/2015 30/09/2019 £316,632
 
Description STFC Studentship
Amount £245,000 (GBP)
Organisation Science and Technologies Facilities Council (STFC) 
Sector Public
Country United Kingdom
Start 10/2016 
End 03/2020
 
Title KinMS_mcmc 
Description Linking the KinMS tools to an MCMC wrapper to better fit SMBH masses as part of the WISDOM project 
Type Of Material Data analysis technique 
Year Produced 2014 
Provided To Others? Yes  
Impact The model has been used by various other groups working in this field. 
URL https://github.com/TimothyADavis/KinMS
 
Description CARS 
Organisation European Southern Observatory (ESO)
Country Germany 
Sector Charity/Non Profit 
PI Contribution I lead the molecular followup of CARS sources, especially those with outflows.
Collaborator Contribution The other team members deal with the MUSE IFU data that forms the basis of the survey, and the ancillary data (radio, X-ray, etc).
Impact First papers incoming shortly.
Start Year 2015
 
Description CARS 
Organisation Leibniz Association
Department Leibniz Institute for Astrophysics Potsdam
Country Germany 
Sector Academic/University 
PI Contribution I lead the molecular followup of CARS sources, especially those with outflows.
Collaborator Contribution The other team members deal with the MUSE IFU data that forms the basis of the survey, and the ancillary data (radio, X-ray, etc).
Impact First papers incoming shortly.
Start Year 2015
 
Description CARS 
Organisation Observatory of Paris
Country France 
Sector Academic/University 
PI Contribution I lead the molecular followup of CARS sources, especially those with outflows.
Collaborator Contribution The other team members deal with the MUSE IFU data that forms the basis of the survey, and the ancillary data (radio, X-ray, etc).
Impact First papers incoming shortly.
Start Year 2015
 
Description CARS 
Organisation University of Cologne
Department Department of Physics
Country Germany 
Sector Academic/University 
PI Contribution I lead the molecular followup of CARS sources, especially those with outflows.
Collaborator Contribution The other team members deal with the MUSE IFU data that forms the basis of the survey, and the ancillary data (radio, X-ray, etc).
Impact First papers incoming shortly.
Start Year 2015
 
Description CARS 
Organisation Yale University
Department Yale Center for Astronomy and Astrophysics (YCAA)
Country United States 
Sector Academic/University 
PI Contribution I lead the molecular followup of CARS sources, especially those with outflows.
Collaborator Contribution The other team members deal with the MUSE IFU data that forms the basis of the survey, and the ancillary data (radio, X-ray, etc).
Impact First papers incoming shortly.
Start Year 2015
 
Description MASSIVE 
Organisation Max Planck Society
Department Max Planck Institute For Extraterrestrial Physics (MPE)
Country Germany 
Sector Academic/University 
PI Contribution I lead the molecular gas aspects of the survey, providing crucial information on the cold phases of the ISM in the most massive galaxies in our universe.
Collaborator Contribution UCB and Princeton staff members primarily supplied the optical IFU information that the survey is based on, while other members provided analysis and ancillary data sets.
Impact 10.1088/0004-637X/795/2/158 10.1088/0004-637X/807/1/11 10.1093/mnras/stv2313
Start Year 2014
 
Description MASSIVE 
Organisation NRC Herzberg Institute of Astrophysics (NRC-HIA)
Country Canada 
Sector Academic/University 
PI Contribution I lead the molecular gas aspects of the survey, providing crucial information on the cold phases of the ISM in the most massive galaxies in our universe.
Collaborator Contribution UCB and Princeton staff members primarily supplied the optical IFU information that the survey is based on, while other members provided analysis and ancillary data sets.
Impact 10.1088/0004-637X/795/2/158 10.1088/0004-637X/807/1/11 10.1093/mnras/stv2313
Start Year 2014
 
Description MASSIVE 
Organisation Princeton University
Department Department of Astrophysical Sciences
Country United States 
Sector Academic/University 
PI Contribution I lead the molecular gas aspects of the survey, providing crucial information on the cold phases of the ISM in the most massive galaxies in our universe.
Collaborator Contribution UCB and Princeton staff members primarily supplied the optical IFU information that the survey is based on, while other members provided analysis and ancillary data sets.
Impact 10.1088/0004-637X/795/2/158 10.1088/0004-637X/807/1/11 10.1093/mnras/stv2313
Start Year 2014
 
Description MASSIVE 
Organisation University of California, Berkeley
Department Department of Astronomy
Country United States 
Sector Academic/University 
PI Contribution I lead the molecular gas aspects of the survey, providing crucial information on the cold phases of the ISM in the most massive galaxies in our universe.
Collaborator Contribution UCB and Princeton staff members primarily supplied the optical IFU information that the survey is based on, while other members provided analysis and ancillary data sets.
Impact 10.1088/0004-637X/795/2/158 10.1088/0004-637X/807/1/11 10.1093/mnras/stv2313
Start Year 2014
 
Description WISDOM 
Organisation Graduate University for Advanced Studies (SOKENDAI), Okazaki
Country Japan 
Sector Academic/University 
PI Contribution I co-lead the team, overseeing strategy, coordinating observing applications and distributing the workload.
Collaborator Contribution The other partners provide expertise, and work on the outputs of the observational program. Some of the research outputs are also being lead from these other institutes.
Impact A figure of merit for black hole mass measurements with molecular gas, MNRAS, 2014, Volume 443, Issue 1, p.911-918 A black-hole mass measurement from molecular gas kinematics in NGC4526. Nature, 2013, 494, 328-330
Start Year 2013
 
Description WISDOM 
Organisation University of California, Berkeley
Department Department of Astronomy
Country United States 
Sector Academic/University 
PI Contribution I co-lead the team, overseeing strategy, coordinating observing applications and distributing the workload.
Collaborator Contribution The other partners provide expertise, and work on the outputs of the observational program. Some of the research outputs are also being lead from these other institutes.
Impact A figure of merit for black hole mass measurements with molecular gas, MNRAS, 2014, Volume 443, Issue 1, p.911-918 A black-hole mass measurement from molecular gas kinematics in NGC4526. Nature, 2013, 494, 328-330
Start Year 2013
 
Description WISDOM 
Organisation University of Hertfordshire
Department Centre for Astrophysics Research (CAR)
Country United Kingdom 
Sector Academic/University 
PI Contribution I co-lead the team, overseeing strategy, coordinating observing applications and distributing the workload.
Collaborator Contribution The other partners provide expertise, and work on the outputs of the observational program. Some of the research outputs are also being lead from these other institutes.
Impact A figure of merit for black hole mass measurements with molecular gas, MNRAS, 2014, Volume 443, Issue 1, p.911-918 A black-hole mass measurement from molecular gas kinematics in NGC4526. Nature, 2013, 494, 328-330
Start Year 2013
 
Description WISDOM 
Organisation University of Oxford
Department Department of Physics
Country United Kingdom 
Sector Academic/University 
PI Contribution I co-lead the team, overseeing strategy, coordinating observing applications and distributing the workload.
Collaborator Contribution The other partners provide expertise, and work on the outputs of the observational program. Some of the research outputs are also being lead from these other institutes.
Impact A figure of merit for black hole mass measurements with molecular gas, MNRAS, 2014, Volume 443, Issue 1, p.911-918 A black-hole mass measurement from molecular gas kinematics in NGC4526. Nature, 2013, 494, 328-330
Start Year 2013
 
Title KinMS 
Description The KinMS (KINematic Molecular Simulation) package can be used to simulate observations of arbitary molecular/atomic cold gas distributions. It is also useful for creating input datacubes for further simulation, for instance to prepare ALMA observations. 
Type Of Technology Physical Model/Kit 
Year Produced 2015 
Impact The routines are written with flexibility in mind, and have been used in various different applications, including investigating the kinematics of molecular gas in early-type galaxies (Davis et al, MNRAS, Volume 429, Issue 1, p.534-555, 2013), and determining supermassive black-hole masses from CO interferometric observations (Davis et al., Nature, 2013, Onishi et al., 2015). 
URL https://github.com/TimothyADavis/KinMS
 
Title KinMS_MCMC 
Description MCMC modelling toolkit that interfaces with KinMS, another product of this award. 
Type Of Technology Physical Model/Kit 
Year Produced 2016 
Impact This tool underpins the research output of the WISDOM team. 
URL https://github.com/TimothyADavis/KinMS_MCMC
 
Description How we caught a glimpse of a supermassive black hole having a meal 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Press Release and Media appearances based around the CARS collaboration and associated papers.
Year(s) Of Engagement Activity 2016
URL https://theconversation.com/how-we-caught-a-glimpse-of-a-supermassive-black-hole-having-a-meal-60736
 
Description Science Storytelling 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact ~50 different people attended two "Stories of Science" events
Year(s) Of Engagement Activity 2017,2018,2019