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2012May 7
Brunetto Ziosi
Physics and Astronomy Department,University of Padua
JC
ATC - Atacama Cosmology Telescope(2008 Southern Survey)
â–ª first light on 22 October 2007â–ª at resolutions of about an arcminute in three frequencies: 145 GHz, 215 GHz and 280 GHzâ–ª will map about two hundred square degrees of the skyâ–ª Atacama desert
WMAP - Wilkinson Microwave Anisotropy Probe
â–ª launched on June 30, 2001â–ª full-sky map of the CMB, with a 13 arcminute resolution via multi-frequency observationâ–ª five discrete radio frequency bands, from 23 GHz to 94 GHzâ–ª L2 orbit
Probe and constrain the primordial power spectrum of adiabatic scalar perturbations
â–ª due to ACT sensitivity: resolution beyond
on the CMB =
probe the primordial power spectrum up to
â–ª constraints on many cosmological parameters from small scales anisotropies in the CMB (which probes early universe physics)
How?
Considerations
by inflation SMs (close to scale invariant)
parametrized with 20 bins in [0.001-0.35] Mpc-1
CDM and baryon physical densities
measure of the angular scale of the first acoustic peak
optical depth at reionization
secondary emissions: SZ from clusters, Poisson and clustered point sources
â–ª limits on the power spectrum bands â–ª no inflation model on the PS to easier comparison with other modelsâ–ª more parameters = better fit but more noise fittingâ–ª one likelyhood point for each parameter alternative models should do betterâ–ª prior on the Hubble constant (degeneracy matter density-PS)
In-depth 2: resolution notes
In-depth 1: the
â–ª removing the
prior: degeneracy between the primordial power
on scales 0.01-0.02 Mpc-1 and the parameters describing
the content and the expansion rate of the universe;this affect the first acoustic peak
â–ª effects exluded by WMAP observation
6 - no significant change in the likelyhood
1 - modify
and move the first acoustic peak (FAP) on larger
(power law) scales, increasing also the amplitude
2 - need a compensation to be in agreement with WMAP measures
3 -
decreases,
decrease,
and
grows to mantain the FAP
amplitude,
decreases to mantain the height
4 - disfavoured by ACT CMB lensing observations
5 - possible constraints relaxation considering a
modified by
massive neutrinos
prior
â–ª due ACT resolution they can constrain the PS to larger values of k (less than 0.19 Mpc-1 instead of 0.15)â–ª primary CMB PS decreases exponentially due to Silk damping at l greater than 2000 while the PS from diffuse emission of secondary sources begins to rise from that l
ACT provides a new window to with wich to constrain any deviation from a standard power law spectrum
â–ª before: no data on l>1000 that is k>0.1 ACT+WMAP improve constraints in 0.1<k<0.19 resulting spectrum consistent with n=0.963
Results
â–ª Markov Chain Monte Carlo on 27 parametersâ–ª CosmoMC
â–ª no scale-invariant spectrum â–ª power law with n=0.956â–ª no running indexâ–ª no significant features in the small-scale power
Results
â–ª comparison with SDSSâ–ª comparison with CMB lensingâ–ª cluster measurement: measurement of the matter power spectrum on a characteristic scale kcâ–ª Lya plot illustrative (different cosmology models or fiducial values fitting rather than direct fit)â–ª mass variance
Reconstructed
at
Conclusions
â–ª they constrain the primordial PS as a function of scale in 20 bands using ACT+WMAPâ–ª no assumption on the smoothness beyond a spline interpolation between bandsâ–ª ACT arcmin resolution = constraints on scales between 0.1 Mpc-1 - 0.19 Mpc-1 not yet well constrained by other CMB experimentsâ–ª test for deviation in a "model independent framework" no deviation from power-law with best fit n=0.968 consistent with a power law model in the LCDM contestâ–ª PS mapped to now and in agreement with galaxies and cluster measurement on larger scales: k~0.001 Mpc-1 corresponding to 1015-1022 Msun
That's all Folks!
Summary
ATC - Atacama Cosmology Telescope
WMAP
Probe and constrain the primordial power spectrum of adiabatic scalar perturbations
Reconstruct and compare
at
temperature or polarization
(CMB temperature angular power spectrum)
for each bin
fitted values
matter perturbationgrowth
matter transferfunction