Kate Land

The Axis of Evil: revisited

astro-ph/0611518, 0502237, 0507289

27/03/07 The Axis of Evil Revisited. Kate Land

THE ISSUESAXIS OF EVIL• Planarity• Alignments• Low-power• Ecliptic issues

OTHER• Asymmetries• Cold spot

27/03/07 The Axis of Evil Revisited. Kate Land

PLANARITY & AOE“Intriguingly, both the quadrupole and the octopole are seen to have power suppressed along a particular spatial axis, which lines up between the two, roughly towards (l, b) ~ (-110, 60) in Virgo.”Tegmark & al.PRD(68)123523

27/03/07 The Axis of Evil Revisited. Kate Land

A posteriori planarity

Quadrupole

l = 2

m = 2 m = 0

27/03/07 The Axis of Evil Revisited. Kate Land

A posteriori planarity

Octopole

l = 3

m = 3 m = 1

27/03/07 The Axis of Evil Revisited. Kate Land

‘Planarity’ is quite normal -

BUT THE AXIS IS NOT!

27/03/07 The Axis of Evil Revisited. Kate Land

Independent of Gaussianity

Hard to test

Axis of Evil

27/03/07 The Axis of Evil Revisited. Kate Land

Maximum Likelihood• Avoid instabilities• Allow model comparison (Bayesian V Freq)

Multipoles share axis, and ratio

27/03/07 The Axis of Evil Revisited. Kate Land

ModelsNull

‘Planarity’ l = 2, 3 m = lParameters:

‘m-preference’ l = 2 - 5 m freeParameters:

27/03/07 The Axis of Evil Revisited. Kate Land

Maximum Likelihood

27/03/07 The Axis of Evil Revisited. Kate Land

SignificanceCompare to simulations

Information criteria‘planarity’ AIC ~ 2, BIC ~ 2.8

‘m-pref’ AIC ~ 2.8, BIC ~ 0Jeffreys’ scale > 2.5 ‘strong’

27/03/07 The Axis of Evil Revisited. Kate Land

Bayesian evidence

27/03/07 The Axis of Evil Revisited. Kate Land

What can we conclude?• Evidence for AOE depends on model and

method!

• Similarly for ns<1 (Liddle astro-ph/0701113)

• Important consequences• Combined with other anomalies• SYSTEMATICS Satellite, data pipeline, …• ASTROPHYSICAL EFFECT Foregrounds,

local lensing, …• COSMOLOGICAL FEATURE Non-FLRW

models, non-trivial topology, …

27/03/07 The Axis of Evil Revisited. Kate Land

The Axis of Evil II - SummaryCorrelations seen for l = 2,3,4,5

But how do we test the significance?Propose a model

Frequentist Bayesian

m-preference

Planarity

27/03/07 The Axis of Evil Revisited. Kate Land

Priors

27/03/07 The Axis of Evil Revisited. Kate Land

Max asym axis (57,10) Ecliptic pole (96,30) SG pole (47,6)

Cold spot (209,-57)

Axis of Evil ~(260,60) Dipole (264,48) Virgo ~(260,70)

27/03/07 The Axis of Evil Revisited. Kate Land

Information criteria

27/03/07 The Axis of Evil Revisited. Kate Land

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