Background on 20 GHz channel

From CMB-S4 wiki
Revision as of 10:42, 6 June 2020 by Flauger (talk | contribs) (Created page with "This posting summarizes the analyses that led to the decision to move the 20 GHz channel from the SATs to the delensing LAT. = Background = During the CDT studies, we notic...")
(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
Jump to navigationJump to search

This posting summarizes the analyses that led to the decision to move the 20 GHz channel from the SATs to the delensing LAT.

Background

During the CDT studies, we noticed a bias for the configuration under study at the time for one of the foreground models. The configuration does not have a number. It can either be thought of as the configuration obtained from configuration 02 by rescaling by a factor sqrt(7/6), or equivalently as configuration 04 but with a 20 GHz channel on the SATs rather than the delensing LAT. For convenience, here is the performance table

Frequency (GHz) 20 30 40 85 95 145 155 220 270
Beam FWHM (arcmin) 76.6 76.6 57.5 27.0 24.2 15.9 14.8 10.7 8.5
white noise level TT (uK-arcmin) 16.66 10.62 10.07 2.01 1.59 4.53 4.53 11.61 15.84
ell knee TT 500 175 175 175 175 230 230 230 230
1/f exponent TT -4.1 -4.1 -4.1 -4.1 -4.1 -3.8 -3.8 -3.8 -3.8
white noise level EE (uK-arcmin) 13.94 8.88 8.42 1.67 1.32 2.12 2.12 5.43 7.42
ell knee EE 200 50 50 50 50 65 65 65 65
1/f exponent EE -2.0 -2.0 -2.0 -2.0 -2.0 -3.0 -3.0 -3.0 -3.0
white noise level BB (uK-arcmin) 13.6 8.67 8.22 1.64 1.30 2.03 2.03 5.19 7.08
ell knee BB 200 50 50 50 50 60 60 60 60
1/f exponent BB -2.0 -2.0 -2.0 -2.0 -2.0 -3.0 -3.0 -3.0 -3.0
ell min 30 30 30 30 30 30 30 30 30
nside 512 512 512 512 512 512 512 512 512

The foreground model that displayed the bias was model 06, which is based on MHD simulations of the ISM.

Closer inspection of the ILC results revealed that the bias originates from synchrotron residuals in bins 4-6 shown in red in the figure below

11.06 ILC.png