A non-linear solution to the S8 tension
We reviewed the evidence for a tension in the value of S8 between Planck CMB and other cosmological observations and proposed a solution. We argue that any discrepancy may be a caused by uncertainties in the theoretical predictions arising from the modelling of the mass fluctuations on non-linear scales. This can either be sourced by non-
We reviewed the evidence for a tension in the value of S8 between Planck CMB and other cosmological observations and proposed a solution. We argue that any discrepancy may be a caused by uncertainties in the theoretical predictions arising from the modelling of the mass fluctuations on non-linear scales. This can either be sourced by non-standard dark matter, or by underestimating the impact of baryon feedback.
See: Amon and Efstathiou 2022;
A tension across scales, rather than across redshifts.
If our proposed explanation of the tension is correct, the required suppression must extend into the mildly non-linear regime, k=0.2h/Mpc.
Baryon feedback: how extreme is too extreme?
We used weak lensing data in combination with CMB measurements of the kinetic Sunyaev Zeldovich (kSZ) effect and Xray measurements of the hot gas to study baryon feedback and its impact on the large scale structure. We found that feedback, as seen by lensing and kSZ, is more extreme than the state-of-the-art hydrodynamical simulations constrain. Bigwood et al. 2022 and Bigwood et al. 2023
Dwarf galaxy mass profiles
We have pioneered a way to extract and characterize large photometric samples of dwarf galaxies using a machine learning technique, using a small, representative spectroscopic sample.
With new data from DESI and LSST, we're excited about our methodology.
See: Thornton, Amon, Wechsler et al (2023)
We've used this to measure the weak lensing mass profiles for one of the lowest mass samples to date.
And to place constraints on the relationship between a galaxy's halo mass and stellar mass in a new regime.
Dark Energy Survey joint weak lensing & clustering cosmology
I played a pivotal role in the Dark Energy Survey Year 3 3x2pt cosmology analysis, leading the weak lensing results and coordinating three analysis teams to the most precise cosmological constraints of its kind, including on the dark energy parameter.
Year 3 Cosmic Shear: I led and coordinated the Dark Energy Survey Year 3 cosmic shear lensing analysis using the most powerful data to date, of 100 million galaxies
We stress-tested these constraints to show that we get consistent results if we change the way we calibrate our data, or if we use subsets of the data.
Estimating GALAXIES' photometric redshifts from their colors
Dark Energy Survey Deep Fields: I co-coordinated this team, responsible for the processing and validation of the deep, optical+NIR fields, crucial for the Year 3 analysis.
SOMPZ: We used machine learning techniques to develop a new method for estimating and calibrating photometric redshifts for the Dark Energy Survey. This method, SOMPZ, incorporates limited NIR data to improve the color-redshift relation.
Cross-survey weak lensing consistency
For the last decade, there have been three independent weak lensing surveys: DES, HSC and KiDS. Their survey data is complementary and the value of having three teams doing the same type of experiment is immense. I have uniquely worked with all three teams and datasets to evaluate the consistency of our measurements, and to forge the best methodology going forwards
We have presented new measurements of the excess surface mass density profiles DES, HSC, KiDS and shown them to be consistent, a program called Lensing without borders. We also jointly analyzed the lensing data with BOSS galaxy clustering to assess their consistency on small and large-scales [Amon and Robertson et al 2022].
More recently,
We have presented new measurements of the excess surface mass density profiles DES, HSC, KiDS and shown them to be consistent, a program called Lensing without borders. We also jointly analyzed the lensing data with BOSS galaxy clustering to assess their consistency on small and large-scales [Amon and Robertson et al 2022].
More recently, the collaborations teamed up for the first joint cosmological analysis -- I played a a leading role. We used an extensive mock analysis to disentangle our different analysis choices and formulate a Hybrid pipeline that was suitable for the joint statistical power - a valuable stepping stone toward analyses with Rubin data.
[DES & KiDS collaborations 2022]
Weak lensing shape calibration
DES PSF and shear estimation
I have worked on validating the Dark Energy Survey's Year 3 galaxy catalogue. Specifically, I tested the shape calibration, point spread function modelling and using image simulations to understand blending, and co-coordinated the shear testing team [11,12,13].
KiDS i-band survey
I processed and analysed the bright-time, single i-band dataset from the KiDS survey, which already spanned >1000 sq. deg. in 2018. I tested the homogeneity of the survey, measured and validated the PSF, shears and redshift distributions and used it as a consistency test of the main KiDS data [Amon, Heymans et al 2017]
E_G: Testing gravity
E_G: Testing gravity
I performed a combined-probe test of General Relativity with weak lensing and spectroscopic data to measure the E_G statistic [Amon+2018]