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ACT. Atacama Cosmology Telescope Funded by NSF Will measure CMB fluctuations on small angular scales Probe the primordial power spectrum and the growth of structure. The M illimeter B olometric A rray C amera: 3000 Detectors. Tri co lor : 145, 225, & 265 GHz

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  • Atacama Cosmology Telescope
  • Funded by NSF
  • Will measure CMB fluctuations on small angular scales
  • Probe the primordial power spectrum and the growth of structure
the m illimeter b olometric a rray c amera 3000 detectors
The MillimeterBolometric ArrayCamera: 3000 Detectors
  • Tricolor:
  • 145, 225, & 265 GHz
  • 3 independent 32x32 arrays
  • TES PUDs from GSFC
  • PUDs = Pop-Up Devices
  • TES = Transition Edge Sensor Each pixel: 1 mm x 1 mm
  • TDM Multiplexing
  • 2-stage 1x33 mux chips, followed by Series Array SQUIDs: SAs -- from NIST
  • Nyquist inductors -- from NIST
  • Mux servo electronics & DAQ from UBC (who provided these for SCUBA)
act collaborations








Government Labs



Kwa-Zulu Natal

…united through research, education and public outreach.


Simulations of mm-wave data.

Survey area

High quality area

150 GHz

SZ Simulation

MBAC on ACT 1.7’ beam


2X noise



where will we be with cmb
Where will we be with CMB

Bond et al.


cosmic timeline for act science
Cosmic Timeline for ACT Science
  • First galaxies
  • Universe is reionized
  • Ostriker-Vishniac
  • Surveys of Sunyaev-Zel’dovich (SZ) clusters
  • Diffuse thermal SZ
  • Kinetic SZ signal

Cosmic Microwave Background

  • N(mass,z) – Evolution of Cosmic Structure
  • Lensing of the CMB
  • The growth of structure is sensitive to w and mn
  • Additional cross-checks from correlations among effects
  • Extraction of cosmological parameters
  • Initial conditions for structure formation


z = 1000

t = 4 x 104 yrs

z = 7

t = 3 x 106 yrs

z = 1

t = 1 x 109 yrs

z = .25

t = 12 x 109 yrs

Primary CMB CMB Lensing OV/KSZ Diffuse Thermal SZ Cluster Surveys

sz signature
SZ Signature

Hot electron gas imposes a unique spectral signature

145 GHz


220 GHz


270 GHz


NO SZ Contribution in Central Band

1.4°x 1.4°

coordinated cluster measurements
Coordinated Cluster Measurements

Identify and measure >500 clusters in an unbiased survey with multi-wavelength observations

Galaxy Cluster

Cosmic Microwave Background

HOT Electrons

  • Mass limits of 3 x 1014 estimated from simulations
  • Science derived from N(mass,z)
southern africa large telescope
Southern Africa Large Telescope

World’s Largest Optical Telescope

SALT has achieved 1” seeing

SALT will survey the ACT strip in 4 colors and will then measure spectra for tens of galaxies per cluster

lensing of the cmb


Lensing of the CMB
  • Lensing arises from integrated mass fluctuations along the line of sight.
  • The CMB acts as a fixed distance source, removing the degeneracy inherent to other lensing measurements.
  • Signal at l = 1000-3000
  • Image distortion – only a minor effect in the power spectrum.
  • Must have a deep, high fidelity map to detect this effect.





1.4°x 1.4°

lensing of the cmb1
Lensing of the CMB





  • RMS signal well above noise floor.
  • Isolate from SZ and point sources spectrally.
  • Identify with distinctive 4-point function.

Lensing Signal

2% of CMB RMS

1.4°x 1.4°

where are the baryons
Where are the baryons?
  • Cross-correlate galaxy counts and kinetic SZ signal
    • KSZ signal proportional to tv
      • Measure TKSZ^2 as a function of galaxy position
      • Use redshift distribution to predict v, correlate density/velocity field and measure W
    • Estimates suggest high S/N detection for ACT and should be much better for 1 mm CCAT
act region target for future lensing surveys
ACT \REGION: Target for future lensing surveys

ACT will begin surveying in 2006

We already plan deep multi-band imaging with SALT of low extinction part of ACT strip (200 square degrees)

Would be a very interesting target for a lensing survey

act is but one of several next generation cmb experiments
ACT is but one of several next generation CMB experiments
  • APEX (Atacama Pathfinder Experiment)
    • UCB/MPI
    • 1.4mm and 2 mm obs.
    • SZ science
  • SPT (South Pole Telescope)
    • 8m at South Pole
    • Chicago group (2008)
    • Large area
      • Optimized for SZ/clusters