planck’s constraints on the missing baryons (pip-105) carlos hernández-monteagudo centro de...

Planck’s constraints on the missing

baryons(PIP-105)

Carlos Hernández-MonteagudoCentro de Estudios de Física del Cosmos de Aragón (CEFCA), Teruel, Spain

On behalf of the Planck collaboration

Outline

The kinetic Sunyaev-Zel’dovich effect (kSZ) The central galaxy catalogue (CGC) Measuring the kSZ pairwise momentum Correlating with a reconstruction of the peculiar

velocity field Constraints on the missing baryons

2Hernández-Monteagudo, "Planck's Constraints on the missing baryons"

The kinetic Sunyaev-Zel’dovich effect

Hernández-Monteagudo, "Planck's Constraints on the missing baryons" 3

• The kSZ effect expresses the Doppler kick experienced by CMB photons when scattering off rapidly moving electrons

• The kSZ temperature anisotropies is independent of frequency (just like primary CMB anisotropies)

• When looking at the direction of hot gas clouds, it is likely to be contaminated by the (dominant) thermal Sunyaev-Zel’dovich (tSZ) effect, which flips from negative to positive at the cross-over frequency of 217 GHz.

• To avoid the tSZ and other contamination, we use different channels and foreground-cleaned maps, like SEVEM, SMICA and NILC.

The Central Galaxy Catalogue (CGC)


• Based upon SDSS DR7 NYUAV galaxy catalogue after isolating brightest galaxies in 1 Mpc (transversal direction) and 1000 km/s (LOS)

• It consists of 262 673 galaxies placed at z~0.12, of which ~83% should be true central galaxies.

• When placing them in a grid, we retain only the 150,000 most nearby ones

Fraction of brightest galaxies that are actually central galaxies in the Millenium simulation (Guo et al. 2011, Planck PIP-XI)

Measuring the kSZ pairwise momentum


• The peculliar kSZ parwise momentum (pkSZ) is built upon quantities evaluated along the line of sight,

• It expresses the gravitational infall/collapse of structure

• The estimates of the kSZ temperature anisotropies are obtained after applying aperture photometry (AP, TAP) on the CGs, with varying aperture

• We subtract the average TAP within a thin redshift shell of width σz ~0.01 (as in Hand et al. 2012, although results do not depend critically on this choice)



We found a colour-free decrement that becomes more significant (up to 4 σ) for the cleaned SEVEM map and for apertures of 8 – 12 arcmin. For SEVEM @ 8 arcmin, a fit to the output of numerical simulations yields S/N ~ 4.5

Error computation


…

[1] [2] … Ncg

AP est.# [0] [1] [2] [3] … [50] We rotate/displace the entire CGC over the CMB maps with no known sources



The behaviour of the kSZ signal wrt aperture is different to what is found in simulated clusters: this constitutes evidence for signal outside halos.

The impact of tSZ seems to be negligible

Hand et al. 2012

Simulated clusters of Dolag & Sunyaev. 2013

Inverting galaxy density into velocity


• Three approaches: LINEAR, LOG-LINEAR, LOG-2LPT

• Impact of mask: LINEAR method most promising after all

We invert the linear continuity equation to estimate the peculiar velocity field from the CG density field

Correlation coefficient

Without maskWith mask

Logarithmic linearisation

Inverting galaxy density into velocity


• Linear reconstruction performs best, S/N ~ 4.6• We normalise recovered velocities to unit RMS• Adopting the velocity amplitude form the

numerical sims, we can infer a value of τT

(Thomson optical depth)

<TkSZ . v/σv >: correlation between kSZ temperature anisotropies and recovered velocities (with RMS=1)

Consistency tests


• We compute correlation after shuffling the recovered velocities among the CGs: the correlation is only recovered for the correct configuration

• The coupling of intrinsic CMB large modes with large spatial modes of the recovered velocities constitutes the largest contribution to the variance: the low-k modes of the recovered velocities are suppressed after shuffling these

Consistency tests


As for the peculiar kSZ pairwise momentum, we find more kSZ signal at apertures close to 8 arcmin (~0.8 Mpc at z~0.12) than at 5 arcmin, and it extends up to ~12 arcmin.

The typical CG virial radius is below 200 Kpc: gas outside halos?

χ2

Aperture [arcmin]

Measuring the amoung of gas


• From the <TkSZ . v/σv > correlation, from the LINEAR approach, we obtain

τT = 1.7+0.6-1.0 x 10-4

• From the kSZ pairwise momentum, we obtain

τT = 2.5 +/- 0.6 x 10-4

• For a typical CG halo we expect

τT = 4 x 10-5

Implications for the missing baryons


τT = σT ne Δg Leff

The Thomson optical depth (τT) is proportional/degenerate to the product of density and length

Leff = 0.8 Mpc

Leff = 38 Mpc

Leff = 105 Mpc

τT = 1.7+0.6-1.0 x 10-4



In this plot, solid lines provide the Δg

(gas overdensity in volumes around CGs) required to reach cosmic density limit in all structures below dobs,max


Leff = 2x0.8 Mpc (spheres)

Leff = 38 Mpc (cylinders)


τT = 1.7+0.6-1.0 x 10-4



In this plot, solid lines provide the Δg

(gas overdensity in volumes around CGs) required to reach cosmic density limit in all structures below dobs,max





τT = 1.7+0.6-1.0 x 10-4

Cylinders centred upon CGs within d=300 Mpc/h occupy a volume fraction fvol= <nCGC> π rp

2 Leff and contain a fraction of the cosmic baryon budget fb :

≠ f(Leff )






τT = 1.7+0.6-1.0 x 10-4

According to Planck, cylinders centred upon CGs up to a distance d=300 Mpc/h contain a fraction of 80+30

-50 % of all baryons. That is, Planck’s observations are compatible to having detected all missing baryons at z~ 0.12

Conclusions


• Planck has measured a pairwise momentum in the direction of central galaxies (CGs) at z=0.12 that is independent of frequency and shows a form very close to expectations from numerical simulations and previous measurements of Hand et al. 2012. The signficance level for frequency maps lies at the level of 3σ, increasing to > 4σ for foreground-cleaned maps.

• The value of the Thomson optical depth from this pairwise momentum is τT = 2.5 +/- 0.6 x 10-4

• After inverting the CG density field into an estimate of the peculiar velocity field, and cross-correlating it to Planck kSZ temperature estimates, we find evidence for bulk flows extending up to ~ 100 Mpc/h with S/N> 4.5. The inferred value for the Thomson optical depth is

τT = 1.7+0.6-1.0 x 10-4

• In both cases, we find evidence for kSZ signal arising outside halos. Accounting for the CG number density, we find that structures contributing to the kSZ around all CGs up to 300 Mpc/h contain 80+30

-50 % of all baryons.

The scientific results that we present today are a product of the Planck Collaboration, including individuals from more than 100 scientific institutes in Europe, the USA and Canada

Planck is a project of the

European Space Agency, with instruments

provided by two scientific

Consortia funded by ESA member

states (in particular the

lead countries: France and Italy)

with contributions

from NASA (USA), and telescope

reflectors provided in a collaboration

between ESA and a scientific

Consortium led and funded by

Denmark.


planck’s constraints on the missing baryons (pip-105) carlos hernández-monteagudo centro de...

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