SKADS Polarization Simulations The MPIfR team (Milky Way & star-forming galaxies): Tigran Arshakian, Rainer Beck, Marita Krause, Wolfgang Reich, XiaoHui Sun The Cambridge team (radio galaxies): Paul Alexander, Dave Green, Julia Riley, N.N.

Independent Beams > 4 SKA specifications Independent Beams > 4

Xilostudios and SKA Project Office SKA Reference Design Xilostudios and SKA Project Office

Projects : SKA Key Science Project: The Origin and Evolution of Cosmic Magnetism Shepherds: Bryan Gaensler & Rainer Beck Projects : All-sky survey of Faraday rotation measures High-resolution polarization mapping of nearby galaxies and clusters Faraday tomography of the Milky Way and nearby galaxies

This needs improvement ! SKA RM Survey Image the whole sky to S  0.1 μJy at 1.4 GHz, FoV ≈ 1 deg2 , 1h / pointing (~1 year total) : RMs for ~(1–5) x 107 polarized extragalactic sources expected, spaced by ~ 60"–90" on the sky This needs improvement !

SKA Design Study - Simulations (SKADS DS2-T1-WP3, MPIfR & Cavendish Lab. Cambridge/UK) Preparing for future SKA projects on magnetism by simulating the polarized sky: Diffuse Galactic emission at high resolution Depolarization and Faraday screens Density of polarized background sources & density of RM grid Simulate RM surveys based on Galactic magnetic field models Important also for BPOL !

SKADS DS2-T1 Polarization Simulations Part 1: Milky Way

RMs of Background Sources Powerful probe of B in the Milky Way, galaxies & clusters Until 2000: RMs of ~1200 polarized extragalactic sources plus ~300 pulsars Galactic plane surveys with ATCA & DRAO: several 100 new RMs New Effelsberg survey (Han & Reich): ~1500 new RMs DRAO Canadian Galactic Plane Survey (Brown et al. 2003, 2004)

All-Sky polarization survey Reich et al. Reich et al. (in prep.), combined from northern sky (Wolleben et al., 2006) + southern sky (Testori et al.)

Simulated PI map at 800 MHz: Models of polarized synchrotron emission Waelkens & Enßlin (MPE Garching), Reich & Sun (MPIfR Bonn) + Ne distribution B-field: regular, reversal Simulated PI map at 800 MHz: regular field field reversal RM map (reversal)

SKADS DS2-T1 Polarisation Simulations Part 2: Galaxies

RMs of background sources behind galaxies Han et al. 1998 RMs of 21 polarized sources shining through M31

RMs through M31 with the SKA (simulation by B. Gaensler) ~10000 polarized sources shining through M31

Galaxies at high z SKA Hopkins et al. (2003) 95% of radio sources at z<3 and >0.1μJy will be star-forming galaxies (Jackson 2004)

The star-formation rate ? The magnetic field ? What determines the total radio luminosity of a galaxy ? The star-formation rate ? The magnetic field ?

Needed: Models of the strength & evolution of magnetic fields in normal galaxies

The gas flow ? The dynamo ? What determines the polarization degree of a galaxy ? The gas flow ? The dynamo ?

M51 (Fletcher, Beck et al. 2006) Spiral galaxies: symmetric fields Low polarization expected at high z

NGC253 (Heesen et al.) Edge-on galaxies: strong regular fields High polarisation expected at high z

NGC4569 (Chyzy et al.) Interacting Galaxies: strong regular fields High polarization expected at high z Replace by Eff

The Antennae (Chyzy & Beck 2004) Merging galaxies: Strong regular field in compression region High polarisation expected at high z

Polarized emission: Results Regular fields form symmetric spiral patterns → weak polarization of face-on galaxies at high z Radio halos are highly polarized → high polarization of inclined galaxies Interaction and ram pressure enhance polarized emission → high polarization at high z

Galaxies at high z Irregular galaxies more frequent IGM denser Interactions more frequent Starbursts more frequent We may expect to see many strongly polarized galaxies at high z

Polarized emission from distant galaxies (SKADS DS2-T1-WP3) Aims : Models of field generation and evolution in star-forming galaxies Degree of field alignment as a function of z Polarization degree as a function of z Faraday rotation and depolarization within galaxies as a function of z → log N / log Sp diagram for polarized sources