US Planck Data Analysis ReviewUS Planck Data Analysis Review

Gary Prézeau US Planck Data Analysis Review • 9–10 May 2006

Adding Polarized Point Sources to Adding Polarized Point Sources to SimulationsSimulations

Development of a polarized point source convolver

2 US Planck Data Analysis Review • 9–10 May 2006Gary Prézeau

Polarized Compact SourcesPolarized Compact Sources

Bright sources contaminate the CMB

– Planck is expected to observe thousands of sources with at least some of them polarized at the few percent level.

Radio-loud active galactic nuclei (AGN’s) almost always contain some detectable amount of polarized light (synchrotron radiation).

Most AGN’s are polarized at less than the 1% level, but approximately 5%-10% of AGN’s are radio loud.

Bright, highly polarized (> 1% level) AGN’s include

– Optically violent variables (OVV’s).

– BL Lac objects.

– Collectively knows as blazars (always radio loud with a relativistically beamed component close to the line of sight).

A few percent of all AGN’s are blazars and may have an observable effect on the measurement of the CMB Stokes parameters (I, Q, U).

At higher frequencies, you also have dusty galaxies.

3 US Planck Data Analysis Review • 9–10 May 2006Gary Prézeau

Polarized Compact Sources as contaminantsPolarized Compact Sources as contaminants

Simulations needed to assess the effect of bright, polarized compact sources on precision measurements of cmb polarization.

Clearly relevant for Planck since one goal is to map ionization history of universe.

Unpolarized point sources can also develop polarization components:

– Cross-polarization: Mismatch between beams of polarized detectors can generate polarization

components of unpolarized compact sources. Beam mismatch (and hence, cross-polarization) can be particularly enhanced

for asymmetric beams.

Unpolarized compact sources are far more numerous than polarized compact sources.

Effect on Q, U components of CMB?

4 US Planck Data Analysis Review • 9–10 May 2006Gary Prézeau

Polarized Compact Sources: ERCSCPolarized Compact Sources: ERCSC

US Planck must deliver the Early Release Compact Source Catalogue (ERCSC).

ERCSC will include

– Unpolarized point sources

It may also include polarized point sources found by Planck.

Simulations of algorithms that identify and extract previously unknown compact sources are crucial.

What is the accuracy with which Planck will be able to identify the polarization angle and percentage of compact sources?

5 US Planck Data Analysis Review • 9–10 May 2006Gary Prézeau

LevelS ‘pntsrcconvolver’LevelS ‘pntsrcconvolver’

In order to perform simulations with compact sources, the simulation package ‘LevelS’ includes a code called ‘pntsrcconvolver’:

– It performs the convolution between point sources and detector beams ∑ (beam) * (point source intensity) over beam width. Convolution can occur over entire sky for any scanning strategy. Allows as input symmetric/asymmetric detector beams. Requires a compact source catalogue as input with compact source

positions in ecliptic coordinate and intensities in Jy.

– Useful for understanding the effect of compact sources on temperature component of CMB for realistic Planck detector beams and simulated sky.

Does not distinguish between polarized and unpolarized detectors:

– Can not be used to answer questions outlined previously. Polarized compact source contamination of Q and U. Compilation of ERCSC.

6 US Planck Data Analysis Review • 9–10 May 2006Gary Prézeau

Polarized pntsrcconvolverPolarized pntsrcconvolver

Polarized pntsrcconvolver ‘p_pntsrcconvolver’ takes into account beam and CMB polarization

– It performs the convolution between point sources and detector beams 0.5*∑ (beam_I *src_I + beam_Q*src_Q+beam_U*src_U) over beam width. Convolution can occur over entire sky for any scanning strategy. Allows as input symmetric/asymmetric detector beams. Requires a compact source catalogue as input with compact source

positions in ecliptic coordinate and intensities in Jy. Also requires polarization angle and percentage for each compact source.

– Can be used for realistic simulations of the data collected by the Planck satellite and eventually split into I, Q, and U components.

7 US Planck Data Analysis Review • 9–10 May 2006Gary Prézeau

Comparisons with other AlgorithmsComparisons with other Algorithms

Pntsrcconvolver is a brute force convolution algorithm.Can compare with other convolution algorithms like the Fourier space algorithm of totalconvolver.– HEALPix temperature maps below

generated with springtide for

nside=128 (27’).

8 US Planck Data Analysis Review • 9–10 May 2006Gary Prézeau

Comparisons with other AlgorithmsComparisons with other Algorithms

p_pntsrcconvolver allows comparisons of Q…

Generated with totalconvolver

Generated with p_pntsrcconvolver

9 US Planck Data Analysis Review • 9–10 May 2006Gary Prézeau

Comparisons with other AlgorithmsComparisons with other Algorithms

… as well as U maps.

Generated with totalconvolver

Generated with p_pntsrcconvolver

10 US Planck Data Analysis Review • 9–10 May 2006Gary Prézeau

Q and U maps of Compact catalogueQ and U maps of Compact catalogue

Catalogue compiled by C. Baccigalupi

11 US Planck Data Analysis Review • 9–10 May 2006Gary Prézeau

In SummaryIn Summary

Polarized compact sources may adversely affect CMB Stokes parameter measurements.

Simulations required for understanding effect of polarized compact sources on CMB Stokes parameters.

Simulations also needed for assessment of algorithms designed to identify and extract compact sources including polarized sources.

p_pntsrcconvolver an essential tool for these simulations which until now did not exist.