Quantifying the rareness of clusters.(and using rareness to constrain new physics)

Shaun HotchkissarXiv:1105.3630 S.H.Home/Dropbox/shared folders/clusters Ian Harrison, S.H.

bonus...arXiv:1104.1145 A. Paranjape, C. Gordon and S.H.arXiv:1108.5458 B. Hoyle, R. Jimenez, L. Verde and S.H*

Summary and motivation

● Planck, ACT, SPT, e-Rosita and XCS are seeing and are going to see 1000's of clusters.

● Pink elephant clusters could be the first evidence of new physics

● There have been claims that some extreme clusters are highly improbable➔ If correct, this could have indicated primordial non-Gaussianity

● All of these claims were the result of a subtle a posteriori bias➔ Examined correctly, no existing cluster or set of clusters are improbable

Ranking “extremeness” is still interesting.

Clusters and non-Gaussianity

Effect of NG on cluster formation

+fNL +skewness+gNL +kurtosis

(+fNL cannot explain voids!)

How can one cluster fool a Fisher analysis?

● Deep into the tail of the distribution the errors aren't Gaussian.● If sufficiently rare, the mere existence of a pink elephant cluster could “rule out” LCDM.

Why are pink elephants interesting

How do you quantify how 'rare' something is?

Early 2011 results.X-rays, etc.

But!which includes these clusters

SPT

Hoyle et al. Enqvist et al. Cayon et al.

Jee et al. Jimenez and verde Hoyle et al.Enqvist et al.Jee et al. (2011)

What were the odds of getting exactly this weekend's lottery

numbers?

M

z

Small R simply isn't uncommon

Equivalent mass at redshift zero

What does unbiased R look like?

What about ensemble rareness?

R1

R2

What if you do it unbiasedly?

(and not conservatively)

As good as it gets right now...

Tension? Maybe... but I wouldn't bet on it.

Can we derive constraints?

Can we derive constraints?

(not without a selection function)

Hypothetical future constraints

Where do we expect the most extreme clusters to appear?

“For standard LCDM structure formation... there should be no giant arcs in the entire sky

as bright in F814W as the observed arc”

Summary and motivation

● Planck, ACT, SPT, e-Rosita and XCS are seeing and are going to see 1000's of clusters.

● Pink elephant clusters could be the first evidence of new physics

● There have been claims that some extreme clusters are highly improbable➔ If correct, this could have indicated primordial non-Gaussianity

● All of these claims were the result of a subtle a posteriori bias➔ Examined correctly, no existing cluster or set of clusters are improbable

Ranking “extremeness” is still interesting.

The Olympics of Space