The ASKAP

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The ASKAP Rotation Measure and Polarization Invest
igaTion (ARMPIT) Bryan Gaensler Sydney
Institute for Astronomy School of Physics The
University of Sydney
C. Fluke
C. Fluke / Reich et al. (2004)
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Cosmic Magnetism

• Something creates maintains coherent µG
  magnetic fields on enormous scales

20 kpc
M51 optical/radio (Stern und Weltraum / Beck et
al. / Hubble Heritage)
Abell 2255 (Govoni et al. 2005)
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ARMPIT Overview

• Co-PIs Gaensler (U. Sydney), Taylor (U.
  Calgary), Landecker (DRAO)
• Wide ARMPIT (commensal with EMU Wide,
  WALLABY)
• - all-sky (d lt 40o) polarised continuum
  at 1.4 GHz
• - rms sensitivity 10 µJy/beam
• - rotation measures (RMs) for 1.5 million
  sources (50 RMs/deg2)
• Deep ARMPIT (commensal with EMU Deep DINGO
  Deep?)
• - deep pointing of single field over
  0.7-1.8 GHz
• - rms sensitivity 1 µJy/beam
• - polarised properties of sources as faint
  as 0.1 mJy/beam
• Diffuse ARMPIT (commensal with FLASH?)
• - shallow all-sky (d lt 40o) diffuse
  polarisation over 0.7-1.8 GHz
• - brightness sensitivity 2-3 mK at 3
  resolution
• - combine w. single-dish data for
  comprehensive view of magnetised ISM

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Wide ARMPIT (1)

• All-sky (d lt 40o) polarised continuum at 1.4
  GHz
• - rms sensitivity 10 µJy/beam
• - rotation measures for 1.5 million sources
  (50 RMs/deg2)
• Science goal 1
• Milky Way as test-bed for problem of how
  large-scale
• magnetic fields are amplified, organised and
  sustained
• - Definitive measurement of strength / direction
  of B in arms and inter-arms
• - Determination of parity of Galactic B above /
  below Galactic plane
• - Spectrum of magnetised ISM turbulence as
  continuous function of l, b
• - Detection / mapping of B in HVCs, SNRs, H II
  regions, etc.

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Wide ARMPIT (2)

• All-sky (d lt 40o) polarised continuum at 1.4
  GHz
• - rms sensitivity 10 µJy/beam
• - rotation measures for 1.5 million sources
  (50 RMs/deg2)
• Science goal 2
• Leveraging a vast sample of background rotation
  measures
• to carry out unique studies of magnetism beyond
  the Milky Way
• - Magnetic structure of all nearby galaxies
• - Definitive census of sources with extreme RMs
• - Statistical examination of B in local clusters
  / super-clusters using bkg RMs
• - Comprehensive study of B vs. time over 0 lt z lt
  3, by correlating RM vs. z

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Deep ARMPIT

• Deep pointing of single field over 0.7-1.8 GHz
• - rms sensitivity 1 µJy/beam
• - polarised properties of sources as faint as
  0.1 mJy/beam2
• Science goal
• Study the polarisation and magnetic fields of
  very faint AGN
• and star-forming galaxies up to a redshift z 2
• - logN - logP down to10 µJy to constrain
  evolution of B in AGN SF
• - Power spectrum of B in intergalactic medium
• - Polarisation properties overall B properties
  of unresolved disk galaxies

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Diffuse ARMPIT

• Shallow all-sky (d lt 40o) diffuse polarisation
  over 0.7-1.8 GHz
• - brightness sensitivity 2-3 mK at 3
  resolution
• - combine w. single-dish data for
  comprehensive view of magnetised ISM
• Science goal 1
• A three-dimensional view of the magnetised ISM
• - Scale height of Galactic B disk/halo
  transition
• - Variation of B w. Galactocentric radius, via
  in situ data on SNRs, PNe, H II
• - Mapping of B in bubbles chimneys,
  cross-correlation with H I and Ha
• Science goal 2
• Large-scale magnetic fields between galaxies
• - Mapping of polarised accretion shocks around
  galaxy clusters
• - Direct detection of synchrotron filaments in
  the IGM

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The Rotation Measure Grid
NVSS RMs (Russ Taylor)
ASKAP simulated polarised sky (10 hours, 1.4 GHz)
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Rotation Measure Synthesis
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Wide ARMPIT High-RM Components

• Probe of extreme densities magnetic fields in
  central engine
• - RMemitted ? (1z)2 , e.g., RMobs 800 rad
  m-2, z 2.8
• ? RMemit 12000 rad m-2
• ? strength / scale of B in NLR, BLR, jets
• (e.g., Zavala Taylor 2004
  OSullivan Gabuzda 2007)
• Geometry unification schemes
• (e.g., Bicknell et al. 1997 Zavala
  Taylor 2002)
• Low and high RM in same source compact component
• ? binary black holes multiple high-RM
  components?

TXS 0402379 (Rodriguez et al. 2006)
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Deep ARMPIT RM vs. Redshift

• RMs at high redshift should be diluted by (1z)2
• Observations to z 2 consistent with
• population of absorbers (galaxies) with
• µG fields over 10 billion years of cosmic
  time!
• (Kronberg et al. 2008 Bernet et al. 2008
  Wolfe et al. 2008)
• Dramatic improvement in
• removal of foreground Galactic RM
• 20,000 RMs ( zH I, zphoto) to derive
• magnetic power spectrum of IGM to z 3

Kronberg et al. (2008)
Kolatt (1998)
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Diffuse ARMPIT The Cosmic Web

• Low-resolution radio images of clusters
• (Kronberg et al. 2007 Pizzo et al. 2008)
• - filaments diffuse synchrotron emission
• on periphery of between galaxy clusters
• - direct probe of cosmic rays and magnetic
• fields in intergalactic space
• (Keshet et al. 2004 Hoeft Brüggen 2007
  
• Ryu et al. 2008 Battaglia et al. 2008)
• Continuum imaging, polarimetry
• Faraday rotation with ASKAP GMIMS
• ? superb probe of magnetised large
• scale structure in local Universe
• ? test of primordial vs outflow for origin
  
• of intergalactic B ? (Donnert et al.
  2008)

Coma field (Kronberg et al. 2007)
MHD simulation of magnetised large-scale
structure (Brüggen et al. 2005)
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Technical Requirements
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Design Study
Management Team (Gaensler, Landecker, Taylor)
Surveys
Calibration Pipeline
Science Simulations
Polarisation leakage
Milky Way
Wide ARMPIT
Wide-field imaging
SNRs, HVCs, H II
Deep ARMPIT
Turbulence
RM synthesis
Diffuse ARMPIT
Nearby galaxies
Single-dish combination
AGN
EMU, WALLABY,
Stacking
Source counts
GMIMS, WHAM,
Source finding cross-IDs
Clusters IGM