UMICH-2015:ChallengeDelensing

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Delensing

Blake Sherwin, Olivier Dore, Chris Sheehy, Josquin Errard, Stephen Feeney, Alex van Engelen, Neelima Sehgal, Hiranya Peiris, Anthony Challinor...


What is the impact of delensing on r, and on nt or BB wiggles?

  • Anthony C - let's think about trying to measure the B-mode spectrum shape
  • Stephen Feeney/Josquin Errand/Peiris/Jaffe: some forecasts of S4 performance on r:

[From Errard*, Feeney*, Peiris and Jaffe (*co-first authors), in prep 2015] Fractional delensing residual after CMB x CMB (solid), CMB x CIB (long-dashed) and CMB x LSS (short-dashed) delensing. We consider cases in which, prior to delensing, synchrotron (light orange), dust (dark orange), or synchrotron and dust (dark red) have been removed, as well as the CMB-only case in which no foregrounds are present (black).

Feeney delens.png

Delens2.png



What sensitivity and resolution do we need for the lensing map?

  • Blake: need high sensitivity lensing map.Plot shows residual delensed B-mode noise on large scales vs. noise of the high-res lens-reconstruction-experiment (right figure from Smith et al. 2010).

BlakeDelens.pngDeLensNoise.png

  • Blake:Improvement from external delensing (e.g. CIB) probably isn't good enough (lensing reduction is only 2-3, compared to ~5 with internal). Combination CIB+noisy lensing can be promising:

DeLensingExt.png DeLensingExt2.png

  • Blake: High resolution is good but not massive gain below few arcmin (figure from CMBPol white paper), assuming source complications for lensing are irrelevant:

DeLensingRes.png


What are the frequency/foreground-removal requirements for the lensing map?

  • I.e. easier to remove foregrounds at small-scales than large

How low a multipole is needed for the lensing-extraction-map?

  • I.e. how is delensing degraded if we have l>50/100/500 etc.