1. 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.

2. Independent Beams > 4
SKA specifications
Independent Beams > 4

3. Xilostudios and SKA Project Office
SKA Reference Design
Xilostudios and SKA Project Office

5. 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

6. 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 !

7. 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 !

8. SKADS DS2-T1 Polarization Simulations Part 1: Milky Way

9. 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)

10. 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.)

11. 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)

12. SKADS DS2-T1 Polarisation Simulations Part 2: Galaxies

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

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

15. 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)

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

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

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

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

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

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

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

23. 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

24. 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

25. 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