0226-it is customary to mask detected point sources in order to eliminate this spurious contribution

CROW

the binned power spectrum values are referred to as bandpowers.

It is often more convenient to work with the lensingmass (convergence) field κ since the lensing potential has a red spectrum while the lensing-mass field has a nearly flat spectrum

In the main line analysis for tensor-to-scalar ratio r (BK-I, BK-VI, BK-X, BK-XIII), the most fundamental guard against systematics are the map jackknife (or null) tests. Maps are made splitting the data into (approximate) halves according to criteria which would be expected to result in nearly equal signal, but potentially different systematic contamination. The split maps are then differenced and the EE, BB and EB spectra of the result compared to simulations of signal plus noise. Well chosen jackknife splits can amplify systematics which cancel in the full coadd map (BK-III). It must be emphasized again that the published BK measurements of the tensor-to-scalar ratio, including the latest BK18 release, have passed all these null tests.

Since the telescope is constantly scanning the sky, a time-varying spurious systematic effect will translate into a position-dependent error in the map, which can be associated with different distortions.

Variations of the actual absolute calibration values between detectors can translate into spatial amplitude modulation of the coadded maps. This amplitude variation could also be introduced by bandpass mismatches (BK-II) between pairs of detectors.

PAPER

Reconstruction of the cosmic microwave background lensing for Planck arxiv:0903.1308

From now on, we move to a full-sky analysis of the CMB lensing effect. Some large areas of the map, where the CMB signal is highly dominated by the foreground emission (e.g. the galactic plane, the point source directions), have to be masked out. Cutting to zero introduces some mode-coupling within the CMB observables. As the lensing reconstruction methods rely on the off-diagonal terms of the CMB data covariance matrix, the map-masking yields some artifacts in the projected potential estimate if not accounted for.

Correlation of CMB with large-scale structure: II. Weak lensing arxiv:0801.0644

The point sources can be subdivided into ‘‘radio’’ sources, which emit via synchrotron and free-free radiation and are brightest (relative to the CMB) at low frequency, and ‘‘infrared’’ sources, i.e., dusty galaxies. The brightest radio sources are usually active galactic nuclei, although star-forming galaxies also emit synchrotron and free-free. Note that it is possible for the same object to be both a radio and an infrared source.

Cross-correlation of CMB with large-scale structure: weak gravitational lensing arxiv:0406004

In some regions of the sky, particularly the Galactic plane, microwave emission from within the Milky Way and from nearby galaxies dominates over the cosmological signal. For their CMB analysis, the WMAP team removed this signal by (i) masking out a region based on a smoothed contour of the K-band temperature, which they denote “Kp2” , and (ii) projecting out of their map microwave emission templates for synchrotron, freefree, and dust emission based on other observations. When analyzing primary CMB anisotropies, it is customary to mask detected point sources in order to eliminate this spurious contribution to the temperature.