COSMOLOGY WITH THE NEW GENERATION OF GALAXY SURVEYS
Lead Research Organisation:
University of Portsmouth
Department Name: Institute of Cosmology and Gravitation
Abstract
My research proposal focuses on three main projects, which in my opinion represent the most exciting fields of contemporary cosmology. The first project discusses the measurement of non-Gaussianity in the distribution of density fluctuations in the Universe. Density fluctuations in the early Universe have been shown to follow a Gaussian form meaning that the distributions of densities around the mean density can be described by only one number, the standard deviation. The current standard model of cosmology includes an inflationary period in the very early Universe, which seeded the large-scale density distributions we observe today. The Gaussian nature of the early density fluctuations is a direct consequence of the inflationary physics. While the simplest model of inflation (single field slow roll inflation) is expected to produce almost perfect Gaussian density fluctuations, other inflationary models can produce significant levels of non-Gaussianity. Such non-Gaussianity would show up as excess large-scale clustering in the galaxy distribution, and hence we can use the distribution of galaxies to test physics that happened within the first second of our Universe's existence.
The second project I discuss in my proposal concerns the sum of the neutrino masses. Study of neutrino oscillations has shown that neutrinos cannot be massless, as proposed in the standard model of particle physics. Therefore neutrinos carry a certain fraction of the matter content of the Universe, which impacts the matter clustering of the Universe. Most cosmic neutrinos are produced during the Big Bang and therefore have a close to relativistic velocity, which allows them to escape the gravitational potential of low mass dark matter haloes. This reduces the clustering of matter on small scales and provides a signal for the measurement of the sum of the neutrino masses using galaxy survey datasets. The cosmological constraints on the sum of the neutrino masses are now more than one order of magnitude lower compared to laboratory experiments and it is expected that the next generation of galaxy surveys will provide a detection of this parameter.
Finally, the third project discussed in my proposal addresses the relative velocity effect. The relative velocity effect describes a relative velocity between baryonic matter and cold dark matter due to physics that happened in the first 300 000 years of the Universe's existence. The relative velocity of these components changes the clustering on very large scales and potentially modifies the Baryon Acoustic Oscillation (BAO) scale. The BAO scale is a special scale in the distribution of galaxies. In our Universe, there are more galaxy pairs separated by 150 Mpc compared to the number of galaxy pairs at 140 Mpc or 160 Mpc. This special scale can be used to map out the expansion history of the Universe using galaxy redshift surveys. The measurement of the BAO scale has emerged as one of the most powerful tools of current cosmology and represents the main science driver for the next generation of galaxy surveys. Given the potential impact of the relative velocity on the BAO scale, studying and measuring the relative velocity effect is essential to ensure the correct interpretation of the BAO scale. Furthermore, a first detection of the relative velocity effect has the potential to alter our understanding of galaxy formation.
The second project I discuss in my proposal concerns the sum of the neutrino masses. Study of neutrino oscillations has shown that neutrinos cannot be massless, as proposed in the standard model of particle physics. Therefore neutrinos carry a certain fraction of the matter content of the Universe, which impacts the matter clustering of the Universe. Most cosmic neutrinos are produced during the Big Bang and therefore have a close to relativistic velocity, which allows them to escape the gravitational potential of low mass dark matter haloes. This reduces the clustering of matter on small scales and provides a signal for the measurement of the sum of the neutrino masses using galaxy survey datasets. The cosmological constraints on the sum of the neutrino masses are now more than one order of magnitude lower compared to laboratory experiments and it is expected that the next generation of galaxy surveys will provide a detection of this parameter.
Finally, the third project discussed in my proposal addresses the relative velocity effect. The relative velocity effect describes a relative velocity between baryonic matter and cold dark matter due to physics that happened in the first 300 000 years of the Universe's existence. The relative velocity of these components changes the clustering on very large scales and potentially modifies the Baryon Acoustic Oscillation (BAO) scale. The BAO scale is a special scale in the distribution of galaxies. In our Universe, there are more galaxy pairs separated by 150 Mpc compared to the number of galaxy pairs at 140 Mpc or 160 Mpc. This special scale can be used to map out the expansion history of the Universe using galaxy redshift surveys. The measurement of the BAO scale has emerged as one of the most powerful tools of current cosmology and represents the main science driver for the next generation of galaxy surveys. Given the potential impact of the relative velocity on the BAO scale, studying and measuring the relative velocity effect is essential to ensure the correct interpretation of the BAO scale. Furthermore, a first detection of the relative velocity effect has the potential to alter our understanding of galaxy formation.
People |
ORCID iD |
Florian Beutler (Principal Investigator / Fellow) |
Publications
Hand N
(2018)
nbodykit: An Open-source, Massively Parallel Toolkit for Large-scale Structure
in The Astronomical Journal
Hand Nick
(2017)
nbodykit: an open-source, massively parallel toolkit for large-scale structure
in ArXiv e-prints
Description | The award was only active for 6 months (switch to an URF), so the project has not been finished. |
Exploitation Route | Myself and my students made code and tools available online https://github.com/minaskar/hankl https://github.com/grnet/zeus https://github.com/fbeutler/pk_tools |
Sectors | Education |
Title | nbodykit: A tool to analyze galaxy survey datasets and nbody simulations |
Description | nbodykit is an open source project written in Python that provides a set of state-of-the-art, large-scale structure algorithms useful in the analysis of cosmological datasets from N-body simulations and observational surveys. All algorithms are massively parallel and run using the Message Passing Interface (MPI). |
Type Of Technology | Software |
Year Produced | 2017 |
Open Source License? | Yes |
Impact | Even though we released the tool just recently it already has been used in several galaxy survey studies (see http://nbodykit.readthedocs.io/en/latest/cookbook/index.html) |
URL | http://nbodykit.readthedocs.io/en/latest/index.html |
Title | www.benty-fields.com: Web application which uses machine learning to help researchers with daily publications |
Description | Benty-fields.com is a web application on which researchers can follow the latest publications (currently working for Arxiv and Socarxiv). It uses machine learning to highlight publications of particular interested to the individual users. |
Type Of Technology | Webtool/Application |
Year Produced | 2015 |
Impact | The application is now used by more than 2000 academics worldwide. |
URL | http://www.benty-fields.com |
Description | blog about research activity and related topics |
Form Of Engagement Activity | Engagement focused website, blog or social media channel |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Public/other audiences |
Results and Impact | I am writing a blog in which I summarize publications for a general audience and discuss questions related to my research |
Year(s) Of Engagement Activity | 2017,2018 |
URL | https://mystatisticsblog.blogspot.com/ |