Issue |
A&A
Volume 507, Number 2, November IV 2009
|
|
---|---|---|
Page(s) | 1087 - 1105 | |
Section | Astronomical instrumentation | |
DOI | https://doi.org/10.1051/0004-6361/200912539 | |
Published online | 15 September 2009 |
Simulated square kilometre array maps from Galactic 3D-emission models
1
National Astronomical Observatories, CAS, Jia 20, Datun Road, Chaoyang District, Beijing 100012, PR China e-mail: xhsun@nao.cas.cn
2
Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany e-mail: wreich@mpifr-bonn.mpg.de
Received:
20
May
2009
Accepted:
13
August
2009
Context. Planning of the Square Kilometre Array (SKA) requires simulations of the expected sky emission at arcsec angular resolution to evaluate its scientific potential, to constrain its technical realization in the best possible way, and to guide the observing strategy.
Aims. We simulate high-resolution total intensity, polarization, and rotation measure (RM) maps of selected fields based on our recent global 3D-model of Galactic emission.
Methods. Simulations of diffuse Galactic emission were conducted using the hammurabi code modified for arcsec angular resolution patches towards various Galactic directions. The random magnetic field components are set to follow a Kolmogorov-like power-law spectrum. We analysed the simulated maps in terms of their probability density functions (PDFs) and structure functions.
Results. We present maps for various Galactic longitudes and latitudes at
1.4 GHz, which is the frequency where deep SKA surveys are proposed. The maps
are about in size and have an angular resolution of about
.
Total intensity emission is smoother in the plane
than at high latitudes because of the different contributions from the regular and random magnetic field. The high-latitude fields show more extended polarized
emission and RM structures than those in the plane, where patchy emission
structures dominate on very small scales. The RM PDFs in the plane are close
to Gaussians, but clearly deviate from that at high latitudes. The RM
structure functions show smaller amplitudes and steeper slopes towards high
latitudes. These results emerge from much more turbulent cells
being passed through by the line-of-sights in the plane. Although the simulated
random magnetic field components distribute in 3D, the magnetic field spectrum
extracted from the structure functions of RMs conforms to 2D in the plane and
approaches 3D at high latitudes. This is partly related to the outer scale of
the turbulent magnetic field, but mainly to the different lengths of the
lines-of-sight.
Conclusions. The significant scatter of the simulated RM distributions agrees with the large scatter of observed RMs of pulsars and extragalactic sources in the Galactic plane and also at high Galactic latitudes. A very dense grid of RMs from extragalactic sources is required to trace and separate Galactic RM foreground fluctuations. Even at high latitudes, total intensity and polarized emission is highly structured, which will contaminate sensitive high-resolution extragalactic observations with the SKA and have to be separated in an appropriate way.
Key words: magnetic fields / polarization / radiation mechanisms: non-thermal / ISM: magnetic field / ISM: structure
© ESO, 2009
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.