5 years ago

A Small-Scale Modification to the Lensing Kernel.

Boryana Hadzhiyska, Joanna Dunkley, David Spergel

Calculations of the Cosmic Microwave Background lensing power implemented into the standard cosmological codes such as CAMB and CLASS usually treat the surface of last scatter as an infinitely thin screen. However, since the CMB anisotropies are smoothed out on scales smaller than the diffusion length due to the effect of Silk damping, the photons which carry information about the small-scale density distribution come from slightly earlier times than the standard recombination time. The dominant effect is the scale dependence of the mean redshift associated with the fluctuations during recombination. We find that fluctuations at $k = 0.01 {\rm \ Mpc^{-1}}$ come from a characteristic redshift of $z \approx 1090$, while fluctuations at $k = 1 {\rm \ Mpc^{-1}}$ come from a characteristic redshift of $z \approx 1200$. We then estimate the corrections to the lensing kernel due to the finite size of the thickness of the surface of last scatter.

We conclude that neglecting it would result in a deviation from the true value of the lensing kernel at the half percent level at small scales. For future high signal-to-noise CMB experiments (e.g., CMB-S4), this corresponds to a $\sim 0.3 \sigma$ shift on scales $k \sim 1 {\rm \ Mpc^{-1}}$.

Publisher URL: http://arxiv.org/abs/1711.03168

DOI: arXiv:1711.03168v1

You might also like
Discover & Discuss Important Research

Keeping up-to-date with research can feel impossible, with papers being published faster than you'll ever be able to read them. That's where Researcher comes in: we're simplifying discovery and making important discussions happen. With over 19,000 sources, including peer-reviewed journals, preprints, blogs, universities, podcasts and Live events across 10 research areas, you'll never miss what's important to you. It's like social media, but better. Oh, and we should mention - it's free.

  • Download from Google Play
  • Download from App Store
  • Download from AppInChina

Researcher displays publicly available abstracts and doesn’t host any full article content. If the content is open access, we will direct clicks from the abstracts to the publisher website and display the PDF copy on our platform. Clicks to view the full text will be directed to the publisher website, where only users with subscriptions or access through their institution are able to view the full article.