The importance of environment for galaxy quenching: starbursts and AGN activity
Lead Research Organisation:
University of Sussex
Department Name: Sch of Mathematical & Physical Sciences
Abstract
To first order, the amount of gas in galaxies is determined by the balance between the accretion of pristine gas from the intergalactic medium and the rate at which gas is converted to stars within galaxies. During starbursts, this balance is strongly offset by extreme star formation rates, which consume gas much more quickly than it can be replenished by accretion. In the local Universe, starbursts are often associated with mergers, raising the question of what the role of galaxy-galaxy interactions in general is for gas depletion and quenching.
Mergers and interactions are just one example of environment-related processes shaping galaxies. In addition to quenching by rapid gas consumption in interaction-induced starbursts, gas removal from galaxies will also lead to the cessation of star formation, albeit on longer times scales. Environment-related quenching mechanisms like ram pressure stripping or strangulation are prime examples of this. They give rise to some of the most characteristic environmental trends at low redshift, e.g. the average overall decrease of star formation in dense regions (the 'SFR-density relation'). Direct and indirect evidence for these processes exists for both individual objects and larger samples in the very dense environment of, e.g., the local Virgo cluster. Overall environmental trends seen in massive clusters are, however, the cumulative result of processing already occurring in smaller haloes with ~1e+13 solar masses - which host galaxy groups - or during their assembly phase.
Even at low redshift, studies of the effects of environment on gas in galaxy groups are currently limited either in angular resolution or to the most massive group members (ALFALFA, GASS). For an in-depth understanding of environment quenching, the star formation efficiency and the resolved spatial distribution of gas and star formation activity should be mapped as a function of different environmental indicators (e.g. position within groups or distance to neighbouring galaxies). In this project the student will use a combination of archival data and new JVLA L-band observations obtained by the project supervisor to address the following questions:
- How do environmental effects in galaxy groups affect the gas fraction and star formation efficiency of galaxies?
- What is the relative importance of (a) feedback from active galactic nuclei (AGN) and (b) gas-consumption during starburst events for producing red and dead elliptical galaxies?
Mergers and interactions are just one example of environment-related processes shaping galaxies. In addition to quenching by rapid gas consumption in interaction-induced starbursts, gas removal from galaxies will also lead to the cessation of star formation, albeit on longer times scales. Environment-related quenching mechanisms like ram pressure stripping or strangulation are prime examples of this. They give rise to some of the most characteristic environmental trends at low redshift, e.g. the average overall decrease of star formation in dense regions (the 'SFR-density relation'). Direct and indirect evidence for these processes exists for both individual objects and larger samples in the very dense environment of, e.g., the local Virgo cluster. Overall environmental trends seen in massive clusters are, however, the cumulative result of processing already occurring in smaller haloes with ~1e+13 solar masses - which host galaxy groups - or during their assembly phase.
Even at low redshift, studies of the effects of environment on gas in galaxy groups are currently limited either in angular resolution or to the most massive group members (ALFALFA, GASS). For an in-depth understanding of environment quenching, the star formation efficiency and the resolved spatial distribution of gas and star formation activity should be mapped as a function of different environmental indicators (e.g. position within groups or distance to neighbouring galaxies). In this project the student will use a combination of archival data and new JVLA L-band observations obtained by the project supervisor to address the following questions:
- How do environmental effects in galaxy groups affect the gas fraction and star formation efficiency of galaxies?
- What is the relative importance of (a) feedback from active galactic nuclei (AGN) and (b) gas-consumption during starburst events for producing red and dead elliptical galaxies?
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| ST/N504452/1 | 01/10/2015 | 31/03/2021 | |||
| 1656789 | Studentship | ST/N504452/1 | 01/10/2015 | 31/05/2019 | Rosemary Coogan |
| Description | Collaboration with galaxy evolution research group at IRFU/SAp CEA Saclay |
| Organisation | Alternative Energies and Atomic Energy Commission (CEA) |
| Department | Institute of Research into the Fundamental Laws of the Universe (IRFU) |
| Country | France |
| Sector | Public |
| PI Contribution | Although the team at Sussex has been collaborating with members of the collaboration for several years, it was the long-term attachment funding offered by the SFTC which allowed us the possibility to more actively renew research activity with this group. At Sussex we have experience calibrating, reducing and manipulating the radio and sub-mm data which is crucial to the study of gas and dust in galaxies, when presented with the raw data. We have experience of specific software used to image and analyse the data. |
| Collaborator Contribution | The team at Saclay have very complimentary experience with the analysis of the above mentioned data. This includes using different pieces of software that in fact allow robust analysis of the data without the bias of imaging the interferometric data, and is very effective for the work I wish to carry out. The team has a number of expertise that I have been able to draw upon during this collaboration, and I have been able to work closely with several people with a wide range of research backgrounds. |
| Impact | Several more publications are currently submitted, near completion or underway, which are a result of the strong collaboration between the research team at Sussex University and the research group at CEA Saclay. |
| Start Year | 2016 |