Observations of anomalous dust emission (AME) with AMI

Clive DickinsonJodrell Bank Centre for Astrophysics, University of Manchester

AMI discussion meeting, U. Cambridge, 30 September 2011

• AME is interesting!

• We think it is electric dipole radiation from small spinning dust grains

• An important foreground for CMB in total-intensity (possibly strongest at ~15-60 GHz)

• If polarized at any level, will be important for CMB in polarization!

• Interesting physical phenomenon

• New diagnostic for studying dust grains

• Complementary to IR

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Why is AME interesting?

Davies et al. (2006)

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Planck confirms spinning dust grains do exist!

Planck early results paper(Planck collaboration et al. 2011)

arXiv:1101.2031 Spinning dust

3-colour image of the Perseus molecular cloud region

• ~15 GHz is close to the peak of AME emission

• Molecular clouds peak ~30 GHz

• Diffuse emission peak ~15 GHz

• Need to understand this!

• 15 GHz probes different grain properties

• Large grains, larger dipole moments...

• Fantastic follow-up instrument e.g. of Planck sources

• Additional angular resolution

• Low frequency side of peak or at the peak

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Why is AMI useful?

Ali-Hamoud, Hirata, Dickinson (2009)

SPDUST

• Survey of Galactic clouds

• Which objects show significant AME, which do not?

• What causes the peak to vary? (grains themselves or the environment?)

• Low frequency side of AME peak (measuring slightly larger grains)

• Follow-up observations from Planck, CBI etc.

• Identify UCHII regions

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What should be done with AMI?

Planck collaboration et al. (2011)

G107.1+5.2

• Christopher Tibbs (ex-Manchester student) now at IPAC, Caltech

• Clive Dickinson, Anna Scaife etc...

• Multiple pointings observed with AMI (2010)

• Perseus molecular cloud known to emit large amount of AME with minimal free-free emission

• COSMOSMOAS (Watson et al. 2005)

• VSA (Tibbs et al. 2010)

• AMI (Tibbs et al., in preparation)

• Aims:

• Confirm AME

• Investigate correlations with FIR/mid-IR templates including PAH indicators

• Investigate environment in detail (c.f. Tibbs et al. 2011)

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AMI observations of Perseus

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AMI observations of Perseus

MIPS 24um - VSA contours

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AMI observations of Perseus

MIPS 24um - AMI 16 GHz contours

Galactic science with the VSA at 33 GHz

VSA Galactic plane survey, l ~ 27o – 46o and |b| < 4o, 13 arcmin beam.

Paper I:1. Searching for AME, 40% of total is AME

2. Map of the Galactic plane

Paper 21. The VSA source catalogue

2. Used 33 GHz to 100 micron and 33 GHz to 2.7 GHz ratios to characterize

sources3. Investigating the clumpiness of the ISM

Proposal – AME in nearby galaxies

A survey of nearby face-on and edge-on HI rich spiral galaxies:

- search for AME (e.g. NGC6946, Scaife et al. 2010)

- deriving statistics of spatial distribution of AME relative to SF regions and spiral arms.

- quantitative studies: percentage of free-free due to AMI.

- estimating diffuse emission

- follow-up studies of selected candidates with EVLA and e-MERLIN.