Adding Polarized Point Sources to Simulations

1. Adding Polarized Point Sources to Simulations Development of a polarized point source convolver

2. Polarized 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. Polarized 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. Polarized 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. 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. Polarized 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. Comparisons 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. Comparisons with other Algorithms • p_pntsrcconvolver allows comparisons of Q… Generated with totalconvolver Generated with p_pntsrcconvolver

9. Comparisons with other Algorithms • … as well as U maps. Generated with totalconvolver Generated with p_pntsrcconvolver

10. Q and U maps of Compact catalogue • Catalogue compiled by C. Baccigalupi

11. In 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.