Dictionary of problems with observations

The data are susceptible to many biases, either from their stochastic nature or from systematics in the data acquisition. We can understand as coming from three broad classes:

  • the angular selection: this one is the easiest but also the most complicated to understand and model. It corresponds to problems that are incurred by the location of the observer. The observation will be susceptible to absorption/contamination due to several conditions that happen along different lines of sights, which changes our capacity to detect the object of interests. In the case of cosmology, we are interested in detecting galaxies typically. The additional complexity of these objects is that, from far away, they look a lot like like individual stars when one considers only wide band photometry.

The radial selection

The angular selection

Light cone evolution

Data application

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