Probing Cosmology with ultra faint dwarf galaxies

Lead Research Organisation: Durham University
Department Name: Physics

Abstract

My research focuses on exploring one of the fundamental unknowns in physics and cosmology: mysterious "dark matter" which makes up 80% of the matter in the Universe. The nature of dark matter is not known but its evidence in galaxies and clusters of galaxies has been observed using its gravitational influence on the matter and light; e.g. affecting the motion of stars in galaxies.
According to the current cosmological model, galaxies inhabit the centre of more extended dark matter halos. The dark matter halos of low mass galaxies (dwarf galaxies) and their fainter counterparts (ultra faint dwarfs or UFDs) are thought to be much more massive than the galaxies themselves. Dwarf galaxies and UFDs are therefore excellent laboratories to explore the properties of dark matter. Due to their low mass and faint nature, however, the study of these objects has been observationally and theoretically challenging. Most of the known UFDs have been discovered only in the very recent years, and theoretical understanding of, and predictions for, these objects are missing from the picture.
During my fellowship, I develop and exploit extremely high resolution simulations of the formation and evolution of UFDs in their dark matter halos using a complex, state-of-the-art galaxy formation model. Such detailed and high resolution models of these extremely faint galaxies have not been possible up to this day.
In my studies, I explore in detail the connection between UFDs and their dark matter halos using my simulations. I will address questions such as what is the dark matter content of UFD and how massive are their dark matter halos? What is the smallest halo that host UFDs? UFDs are amongst the first galaxies to form in the Universe after the Big Bang. I follow the formation of these objects in their dark matter halos and explore their different formation channels. Moreover, I study how these first galaxies affect their environment when the Universe was very young.
Most of the currently known UFDs are located close to us, i.e. around our own galaxy, the Milky Way, and are satellites of the Milky Way. More of these extremely faint objects are expected to be discovered in the following years using up-coming telescopes, e.g. the Extremely Large Telescope. It is however not known how many more UFD are awaiting discovery. Using my research, I predict how many UFDs are expected to exist around the Milky Way and how they are distributed. My findings will guide the search for the missing dwarfs and UFDs in the up-coming years.
In summary, I study the formation and evolution of ultra faint dwarf galaxies in a cosmological context in order to understand the connection between dark matter halos and galaxies at the faint end, and to provide predictions for the up-coming telescopes (e.g. the Extremely Large Telescope and the James Webb Space Telescope) which are expected to discover more of these galaxies in the nearby Universe, as well as early times.

Planned Impact

This proposal is addressing some of the fundamental questions in physical sciences about how the Universe and galaxies within, formed and evolved; and it will ultimately shed light on the nature of ''dark matter''. The mysterious dark matter builds up 80% of the matter in the Universe, and yet we do not know what it is. Understanding its nature has profound consequences for science.
Through this proposal I will develop and exploit computer models (simulations) which will compete with the best efforts in the world and will advance on them in terms of the level of detail. Therefore, this proposal will help in international recognition of UK's science in short (during the course of the fellowship) and medium terms.
Besides the astrophysics scientific community (field of this research), the scientific outcome of this proposal will impact wider academic research on the fundamental laws of nature; e.g. particle physics, string theory, or gravity. The impact will happen both on short and long time scales.

Private sector (indirect impact): The complexity of the simulations that I develop and their large computational cost, can motivate the design of new algorithms and specialised hardware, in partnership with computer scientists and engineers. Additionally, the foundation of these simulations (fluid mechanics) are applicable in industries such as aerospace and automobile.

Third sector (direct impact): Astronomy is a very visual science. Science museums can potentially benefit directly from the outcome of this proposal, since cosmological simulations have the potential to produce inspiring and/or interactive visual material which are excellent for educational purposes.

Wider public: This proposal will contribute to the basic human knowledge and benefit the general public, nationally and internationally, in both the short and long term. In particular, members of the local communities and the general public in the UK will benefit from it in the short term due to public engagement activities of the PI. (Please refer to "Pathways to Impact" document for more detail).

Publications

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Belokurov V (2023) Energy wrinkles and phase-space folds of the last major merger in Monthly Notices of the Royal Astronomical Society

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Blanchette K (2023) Velocity-dependent J-factors for Milky Way dwarf spheroidal analogues in cosmological simulations in Journal of Cosmology and Astroparticle Physics

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Borukhovetskaya A (2022) Galactic tides and the Crater II dwarf spheroidal: a challenge to LCDM? in Monthly Notices of the Royal Astronomical Society

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Borukhovetskaya A (2022) The tidal evolution of the Fornax dwarf spheroidal and its globular clusters in Monthly Notices of the Royal Astronomical Society

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Borukhovetskaya Alexandra (2021) Galactic tides and the Crater II dwarf spheroidal: a challenge to LCDM? in arXiv e-prints

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Deason A (2023) Unravelling the mass spectrum of destroyed dwarf galaxies with the metallicity distribution function in Monthly Notices of the Royal Astronomical Society

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Deason A (2022) Dwarf stellar haloes: a powerful probe of small-scale galaxy formation and the nature of dark matter in Monthly Notices of the Royal Astronomical Society

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Evans T (2022) Observing EAGLE galaxies with JWST : predictions for Milky Way progenitors and their building blocks in Monthly Notices of the Royal Astronomical Society

 
Description We have shown that the dark matter content of dwarf galaxies that are relatively large for their stellar mass (e.g. Crater 2 and Antlia 2), can be in tension with LCDM predictions from hydrodynamical simulations.
We have shown that the abundance and extent of ultra faint dwarf galaxies are a powerful prob of the nature of dark matter and galaxy formation. We provided predictions based on semi-analytic models.
We are running very high resolution simulations of these systems and we will be able to provide more accurate predictions based on hydrodynamical galaxy formation simulations.
Exploitation Route As a pure science proposal, the outcome can be used for educational purpose (public outreach) or the big datasets produced through the simulations can be used to train student for data analysis and programming.
Sectors Digital/Communication/Information Technologies (including Software)

Education

 
Description NAM
Geographic Reach National 
Policy Influence Type Participation in a guidance/advisory committee
 
Description STFC's DiRAC panel
Geographic Reach National 
Policy Influence Type Membership of a guideline committee
 
Description LYRA 
Organisation Max Planck Society
Department Max Planck Institute for Astrophysics
Country Germany 
Sector Academic/University 
PI Contribution The PI, her PhD student and PDRA are working on projects with the LYRA collaboration, which is directly linked to the grant objectives. The phd student is analysing the simulations run in this collaboration. The outcome of this will scientifically benefit the whole collaboration. The PDRA (funded by this grant) is working on developing a new suite of high resolution simulation in this collaboration. I contribute by supervising those projects as well as helping with making initial condition for the simulation.
Collaborator Contribution Making software and hardware (simulation code and access to the data) available to us.
Impact No output yet
Start Year 2021
 
Description Virgo - LJMU 
Organisation Liverpool John Moores University
Department Astrophysics Research Institute
Country United Kingdom 
Sector Academic/University 
PI Contribution The PI co-supervises a student at LJMU who works with the PI on topics related to this award
Collaborator Contribution The numerical simulations developed by the student at LJMU will be used by the PI and her team in relation to the scientific objective of the award
Impact outputs are under prep
Start Year 2020
 
Description Virgo - Leiden 
Organisation Leiden University
Department Leiden Observatory
Country Netherlands 
Sector Academic/University 
PI Contribution The outcome of the computer simulations my research team is developing will complement their efforts.
Collaborator Contribution My research team uses the numerical tools developed by collaborators at Leiden
Impact outputs and publications under development
Start Year 2020
 
Description Durham Orchestra 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact a concert with a science theme (planets) -- astronomy related outreach talks were organised to acompany the music side of the program.
Year(s) Of Engagement Activity 2023
 
Description Eyes 2 the sky 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Schools
Results and Impact Eyes to the Sky is a STFC funded science (astronomy) outreach program. I attended multiple events as a scientist collaborating with the project.
I participated (online) to the event for 3 schools.
At each event (school) we reached ~20 pupils.
We show great engagement by the young pupils with space science.
The program has been very successful - so funding has been applied for a second round.
Year(s) Of Engagement Activity 2022
URL https://4fvirtual.org.uk/eyestothesky/
 
Description Girls Day 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact ~60 female students from 6-7 schools visited the research institute .
There were various science demos and talks organised for the pupils.
Year(s) Of Engagement Activity 2023
URL https://durham-astro-girlsday.com/
 
Description School Visit 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact Visited 2 secondary schools in the county, alongside other colleagues from astronomy, and showed up in their science classrooms and told them about our research - interacted with a total of ~200 pupils in year 8 and 9.
Year(s) Of Engagement Activity 2022