From precision to accuracy: cosmology with large imaging surveys
Hiranya Peiris
University College London
Photometric surveys are often larger and extend to fainter magnitudes than
spectroscopic samples, and can therefore yield more precise cosmological
measurements. However, photometric data are significantly contaminated
by multiple sources of systematics, either intrinsic, observational, or
instrumental. These systematics affect the properties of the raw images
in complex ways, propagate into the final catalogues, and create spurious
spatial correlations. Some of these correlations may also be imprinted
in spectroscopic catalogues, since the latter rely on targets selected
from imaging data. Therefore, not just precise ~W but also accurate ~W
cosmological inferences from imaging surveys require careful mitigation of
spatially-varying systematics. I will present a new framework of extended
mode projection to robustly mitigate the impact of such systematics on
power spectrum measurements. I will demonstrate the effectiveness of
the technique, showing constraints on primordial non-Gaussianity using
the clustering of 800,000 photometric quasars from the Sloan Digital
Sky Survey in the redshift range 0.5 < z < 3.5. Finally, I will present
a framework to map the observing conditions of the Science Verification
data in the Dark Energy Survey (DES) and incorporate them into end-to-end
simulations of the DES transfer function. The considerations presented
here are relevant to all multi-epoch surveys, and will be essential for
exploiting future high-cadence surveys such as the Large Synoptic Survey
Telescope (LSST), which will require detailed null-tests and realistic
end-to-end image simulations for correct cosmological inferences.
Date: | Jeudi, le 9 avril 2015 |
Heure: | 15:30 |
Lieu: | Université McGill |
| McGill Space Institute (3550 University), Conference Room |
Contact: | Robert Rutledge |
|