Separating the Intrinsic Alignment Signal and the Lensing Signal using
  Self-Calibration in Photo-z Surveys with KiDS450 and KV450 Data
  To reach the full potential for the next generation of weak lensing surveys,
it is necessary to mitigate the contamination of intrinsic alignments (IA) of
galaxies in the observed cosmic shear signal. The self calibration (SC) of
intrinsic alignments provides an independent method to measure the IA signal
from the survey data and the photometric redshift information. It operates
differently from the marginalization method based on IA modeling. In this work,
we present the first application of SC to the KiDS450 data and the KV450 data,
to split directly the intrinsic shape - galaxy density (Ig) correlation signal
and the gravitational shear - galaxy density (Gg) correlation signal, using the
information from photometric redshift (photo-z). We achieved a clear separation
of the two signals and performed several validation tests. Our measured signals
are found to be in general agreement with the KiDS450 cosmic shear best-fit
cosmology, for both lensing and IA measurements. For KV450, we use partial
(high-z) data, and our lensing measurements are also in good agreement with
KV450 cosmic shear best-fit, however, our IA signal suggests a larger IA
amplitude. We discussed the impact of photo-z quality on IA detection and
several other potential systematic biases. Finally, we discuss the potential
application of the information extracted for both the lensing signal and the IA
signal in future surveys.
