I'm Dr. Ryan Turner, a cosmologist and science communicator.
I use the peculiar motions of galaxies to learn about the evoultion of the Universe
and to measure its expansion, in order to answer some of cosmology's biggest questions.
About Me
I am a Postdoctoral Research Associate at Swinburne University of Technology in Melbourne, Australia. I am interested in all things cosmology, but the focus of my research is in peculiar velocity cosmology. I use statistical methods to measure the growth rate of large-scale structure and expansion history of the Universe to test cosmological models and theories of gravity, better understand dark energy, and resolve the Hubble tension. I am also interested in large spectrographic surveys, and I am a member of the Dark Energy Spectroscopic Instrument (DESI) and the 4MOST Hemisphere Survey (4HS) collaborations, as well as the ARC Centre of Excellence for Gravitational Wave research (OzGrav). My general scientific interests are:
- Peculiar velocities
- Statistics
- Large-scale structure
- Dark energy
- Spectroscopic surveys
- Weak lensing
- Baryon acoustic oscillations
Some of my presentations have been recorded and uploaded to YouTube, you can find them below:
Click here to check out my performance during Melbourne International Comedy Festival
Click here to see the talk I prepared for Cosmology from Home 2022
Research
Peculiar Velocities
All galaxies have velocities that are some combination of their movement in an expanding universe and their peculiar motion. Galaxy peculiar velocities are caused by the gravitational influence of large-scale structure, and thus can be used as a probe of the underlying distribution of matter in the Universe. I use peculiar velocities to constrain the growth rate of structure in the Universe, which can be used as a direct test of General Relativity and modified theories of gravity.
Velocity Field Reconstructions
The galaxy density field is related to the peculiar velocity field in linear theory, and so we can use the observed galaxy distribution in a volume to infer the velocity field at any point in that volume. I use a modified version of techniques used to reconstruct the Baryon Acoustic peak in order to make accurate reconstructions of the velocity field that can be used to improve redshift measurements for local distance indicators such as Type Ia supernovae and gravitational wave events.
Below are some key figures from my recent work:
An excerpt from a plot showing the improvement in cosmological constraints when cross-correlating galaxy clustering and peculiar velocity statistics.
A plot showing that an improved method of linearly reconstructing the velocity field can produce unbiased measurements of the growth rate
A plot summarising recent measurements of the growth rate made using various datasets and methodologies, showing their consistency with the standard cosmological model
Publications
A full list of my publications can be found on ADS or my ORCID page, here are a selection of my most recent first-author publications:
Turner, R. J. et al., "Cosmology with Peculiar Velocity Surveys", arXiv pre-print, arXiv:2411.19484
Turner, R. J. et al., "Biases in velocity reconstruction: investigating the effects on growth rate and expansion measurements in the local universe", Monthly Notices of the Royal Astronimcal Society, vol. 526, issue 1, Nov 2023, Pages 337-346, https://doi.org/10.1093/mnras/stad2713
Turner, R. J. et al., "A local measurement of the growth rate from peculiar velocities and galaxy clustering correlations in the 6dF Galaxy Survey", Monthly Notices of the Royal Astronimcal Society, vol. 518, issue 2, Jan 2023, Pages 2436-2452, https://doi.org/10.1093/mnras/stac3256
Contact
Feel free to contact me at rjturner[at]swin.edu.au, or get in touch on social media following the icons located on the sidebar.