We work on a variety of projects analyzing existing datasets in order to constrain our cosmological model and astrophysical phenomena related to galaxy formation and evolution. The main datasets we currently investigate originate from the Dark Energy Survey, the Dark Energy Spectroscopic Instrument, and public CMB datasets from Planck, South Pole Telescope and Atacama Cosmology Telescope.
When combining these datasets the main question is whether the cosmological probes included are statistically correlated or independent. In the latter case the individual analyses can be performed independently and combined at the level of their posterior probabilities. If probes are correlated the situation becomes much more complex and all observables need to be forward-modeled in a joint analysis as a function of the underlying cosmological and systematics parameters.
Our lab is pursuing several directions in terms of joint, multi-probe analyses. We are experts in modeling the required joint, analytical covariance matrices that capture the statistical correlations of observables that originate from the fact that they trace the same underlying matter density field.
Some cosmological observables, e.g. weak lensing and galaxy clustering, are statistically correlated since they trace the same underlying dark matter structure.
Combining weak lensing, galaxy clustering, CMB lensing, and their cross-correlations
In this project we explore analysis strategies to combine cosmological probes extracted from photometric data with CMB lensing.
Weak lensing and photometric galaxy clustering are extracted from Dark Energy Survey data, which is then combined with CMB lensing data from Planck, SPT, and/or ACT.
This type of analysis will be even more interesting with data from LSST and Roman in combination with latter stages of ACT and SPT and then with Simons Observatory and CMB-S4. These next generation analyses will require new models for astrophysical and observational systematics such that the increase in data quality is translated into additional constraining power on cosmological parameters.
Combining weak lensing, galaxy clustering, galaxy clusters, and their cross-correlations
Including information from galaxy clusters into the standard analysis of galaxy weak lensing and galaxy clustering is another powerful combination of cosmological probes.
In principle, the number density of galaxy clusters as a function of their redshift and mass is an excellent source of cosmological information, however, several aspects make this probe complicated to model. Firstly, galaxy clusters need to be identified as such and secondly, estimating their mass is complicated in itself.
Our lab is pursuing several projects that aim to develop the full potential of galaxy clusters as a cosmological probe.
Combining photometric and spectroscopic surveys
Spectroscopic surveys such as DESI measure the precise redshift of galaxies by taking spectra of the galaxy light, which allows us to map the 3-dimensional distribution of the galaxy density field. Photometric surveys such as DES and LSST only measure the flux of galaxies over a few different wavelength ranges, which only gives approximate redshift information. As a result photometric surveys measure projections of the 3D matter density field and can at best slice the 3D matter field into a few tomographic redshift bins.
Photometric surveys can however map the galaxy distribution much faster and deeper than spectroscopic surveys, which makes it useful to combine the two in a joint analysis.
Our lab is developing a joint analysis framework for 2D+3D analyses that is based on a combination of DES and DESI data right now, which will evolve to conduct 2D+3D data analyses using LSST and DESI/SPHEREx, and Roman spectroscopic and imaging data as well.