Edge: Engineering Dwarfs at Galaxy formation's Edge
Lead Research Organisation:
University of Surrey
Department Name: Physics
Abstract
In this project the student will run new simulation of isolated dwarf galaxies in their full cosmological context. The project will make use of a new photon transport model in the RAMSES code, and an algorithm for genetically modifying simulated galaxies to perform controlled numerical experiments of the effect of mergers and environment for the first time.
Organisations
People |
ORCID iD |
| Justin Read (Primary Supervisor) | |
| Matthew Orkney (Student) |
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| ST/N504440/1 | 01/10/2015 | 31/03/2021 | |||
| 1941677 | Studentship | ST/N504440/1 | 01/10/2017 | 31/03/2021 | Matthew Orkney |
| ST/R505134/1 | 01/10/2017 | 30/09/2021 | |||
| 1941677 | Studentship | ST/R505134/1 | 01/10/2017 | 31/03/2021 | Matthew Orkney |
| Description | As a direct result of this funding, I have produced a suite of cosmological "zoom" simulations of dwarf galaxies, submitted two lead-author research papers (with a third in an advanced state of completion) along with several co-authored papers, and exhibited my research at conferences, various research institutions, and to the general public. The primary research objective of this work was to investigate the "Cusp-Core problem" in dwarf galaxies. The Cusp-Core problem relates to the central dark matter densities in galaxies, where observational methods find typically lower central densities than simulations using a Cold Dark Matter cosmology. Prior work has established that this discrepancy can be solved by modelling baryonic physics in simulations, which act to transform dense central densities (cusps) into lower, or even constant, central densities (cores). Through the use of cosmological galaxy simulations, my work has affirmed prior understanding that cusp-core transformations become inefficient in dwarf galaxies of lower stellar mass, and also identified a novel mechanism by which the central dark matter density in dwarf galaxies can be further reduced through impulsive heating from minor mergers. This mechanism is typically sub-dominant to the traditional baryonic physics mechanisms, but can nonetheless have important implications on the dynamics of the faintest dwarf galaxies. My work then investigates the implications of these cusp-core transformations on the properties of an unusual ultra-faint dwarf galaxy, Eridanus II. I use a suite of star cluster simulations to show that it is difficult to justify the existence of the star cluster that is observed within Eridanus II, and that more exotic cosmologies beyond Cold Dark Matter may be needed. I also investigate the shapes of the dark matter halo within my cosmological simulations. Prior work has shown that baryonic physics can lead to a rounding of an otherwise prolate halo shape, but it was not clear whether this rounding would still occur in the faintest dwarf galaxies. I predict that the faintest, most gas-poor, dwarf galaxies retain a prolate halo shape over all radii. In addition to my primary goals, I also researched whether the granularity of dark matter substructure could be probed by measuring the accelerations of tracers, such as stars. I found that the method could hypothetically distinguish between a range of cosmologies, but that the observational precision required would not be seen in the near future. Similarly, I explored whether luminous gas associated with dark matter substructure could be used to distinguish between cosmologies, but found that the brightness was likely far below current detection limits. |
| Exploitation Route | The outcomes of this funding have directed the investigations of new PhD students and postdocs. In addition, the simulation suites that have been run as a result of this funding have formed the bedrock for several other projects, and have informed the development of new simulation suites. Some of the analysis tools developed over the course of this funding have seen use by other members of the scientific community, both within and outside my host institution. |
| Sectors | Other |
| Title | Contribution to the python module pynbody |
| Description | My contribution to this Python package consists of a function that will estimate the shape of a distribution of points, assuming ellipsoidal symmetry. This is used to find the shape and orientation of homoeoidal shells in simulated dark matter halos. |
| Type Of Technology | Software |
| Year Produced | 2018 |
| Open Source License? | Yes |
| Impact | None as of yet |
| URL | https://github.com/pynbody/pynbody/pull/487 |
| Description | Flash talk and poster at the COSMO-DWARFS conference (Durham University) |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Postgraduate students |
| Results and Impact | COSMO-DWARFS was an astrophysics conference held at Durham University on the subject of dwarf galaxies. The conference was attended by approximately 130 people, ranging from PhD students to Professors. During the conference I presented a flash talk (2 minutes in length) on my research topic, which was accompanied by a digital poster. I used the opportunity to discuss my project with collaborators and others. |
| Year(s) Of Engagement Activity | 2019 |
| URL | http://astro.dur.ac.uk/cosmodwarfs/index.html |
| Description | Poster at the European Astronomical Society (EAS) virtual conference |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Postgraduate students |
| Results and Impact | I presented an interactive poster titled "EDGE: star clusters as probes of dark matter cores in ultra-faint dwarfs". |
| Year(s) Of Engagement Activity | 2021 |
| Description | Public outreach talk (University of Surrey) |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | Local |
| Primary Audience | Public/other audiences |
| Results and Impact | Between 70 and 80 members of the general public of all ages attended an official "Stargazing Night" event which runs monthly over the winter period. The first half of the event includes a 45 minute presentation with 15 minutes questions. I provided the presentation on the subject of cosmological galaxy simulations. The audience responded well to the presentation and I continued to discuss the subject with a few of the audience members for over an hour afterwards. |
| Year(s) Of Engagement Activity | 2020 |
| Description | Recurring cross-departmental meetings with MSSL (Mullard Space Science Laboratory) |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | Regional |
| Primary Audience | Postgraduate students |
| Results and Impact | I co-organise a (typically) monthly cross-departmental meeting between the Surrey astrophysics research group and the Mullard Space Science Laboratory (MSSL). These meetings run for between 1.5 and 2 hours, and involve postgraduate students, post-doctoral students, and professors. Each meeting consists of several short presentations, followed by a discussion session. I have presented my own research on two occasions. |
| Year(s) Of Engagement Activity | 2019,2020 |
| Description | Seminar at the ICCUB (University of Barcelona) |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | Local |
| Primary Audience | Postgraduate students |
| Results and Impact | I have a 45-minute seminar, followed by 15-minutes of questions, to the astrophysics department at the University of Barcelona. The title of this seminar was "EDGE: Investigating the many mysteries of Eridanus II's star cluster". |
| Year(s) Of Engagement Activity | 2022 |
| Description | Talk at the European Astronomical Society (EAS) virtual conference |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Postgraduate students |
| Results and Impact | I gave a 15 minute talk titled "The multiple paths to dark matter core formation in low-mass dwarf galaxies" to an audience of undergrad and postgrad members of the scientific community. |
| Year(s) Of Engagement Activity | 2020 |