cosmology with act photo of the atacama cosmology telescope by michele limon mark halpern, ubc
TRANSCRIPT
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Cosmology with ACT
Photo of the Atacama Cosmology Telescope by Michele Limon
Mark Halpern, UBC
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AtacamaCosmologyTelescope
Optical
X-ray
Theory
Columbia HaverfordU. KwaZulu-NatalRutgers U. Catolica
Cardiff
UMassCUNY
UBCNISTINAOE NASA/GSFC
UPenn U. Pittsburgh U. TorontoPrinceton
Collaboration:
A program designed to measure the high-l features of the CMB
ACT is a 3-color off-axis 6m telescope. Beam sizes are 1-2 arc minutes, corresponding to 400< l <7000
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The CMB is still a scientific gold mine.
Small scale anisotropy
Polarization at all angular scales
Better known parameters
Non-gaussianity?
Non-adiabatic modes ?
Neutrino mass?
Measure w(z)
Formation and growth of cosmic structure.
Tests of field theories at 10-35 s.
Something new?
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The overall tilt of the spectrum--- encoded in the “scalar spectral index” ns--- is a new handle on inflation.
Tilt of the Angular Power Spectrum.One example…
Polarization experiments will help resolve r.
Expect results from Planck, Clover, Spider, Ebex, Spud, Bicep, Poincare, bPol, CMB-pol. This is an active field.
Expts in red use UBC TES electronics and NIST-style multiplexors.
ACT and other small scale measurements will resolve ns.
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A 2% variation in ns produces a 5% variation in primary anisotropy at l = 2500.
The relative calibration of WMAP and ACT must be known to <1% to provide useful data. This is easier than knowing the WMAP beam shape well enough.
Comparison of WMAP and ACT spectra will provide a useful measurement of ns.
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ACT will also probe secondary anisotropies which arise during the epoch of structure formation
Sunyaev Zeldovich effect from clusters
Gravitational Lensing of the CMB
Vishniac Effect and Kinetic SZ
Foreground point sources
Epoch of cluster formation
Measure w(z)
Measure mass spectrum
Star formation history
Photo from Act towards llano de Chajnantor by Michele Limon
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SZ Signature: Non-CMB spectrumHot electron gas imposes a unique spectral signature:
photon number is preserved while photons scatter to higher energy
NO SZ Contribution in Central Band
145 GHzdecrement
220 GHznull
270 GHzincrement
1.4°x 1.4°
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Valageas, Balbi &Silk Astro-ph 0009040
Thomson Scattering and structure in either the velocity or the density of free electrons produce a secondary anisotropy.
The frequency spectrum (color) of the anisotropy matches the CMB.
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From Wayne Hu, Astro-ph 9907103
Linear Effects: OV
Structure in ne not correlated with bulk v.
Non-linear: kSZ
Clusters have formed. Cluster velocity produces signal
ACT will measure the matter power spectrum in both linear (Ostriker-Vishniac) and non-linear (kinetic Sunyaev-Zel’dovich) growth regimes.
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The ACT angular resolution is needed to study SZ.
1.40
150 GHz SZ Simulation MBAC on ACT 2X noise
Planck
MAP
PLANCK
Statistical uncertainties based on 1 season with best measured noise.
de Oliveira-Costa
Burwell/Seljak
1.7’ beam
ACT
WMAP
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Photo by Michele Limon
The ground screen under construction at Cerro Toco.
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A view looking down the face of the primary, before the panels were installed
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Panels Installed
Each panel of the primary mirror is adjusted by hand and locked in place.
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Large sensitive arrays of superconducting Transition Edge Sensor bolometers are at the heart of ACT.
We build the control and readout electronics for these arrays.
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Photo: Mike Neimack
The ACT 145 GHz array, fully assembled.
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• Also plot as power in detector vs voltage
• Power constant in superconducting transition
• Power proportional to V2 in normal state
• Responsivity (S) in transition proportional to 1/V
Decreasing heater power
Load curves
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Feedback Error signal
Optical response of five bolometers:
This is 10 kHz readout of a sub-pW optical signal.
(Data collected at UBC on a cryostat in New Jersey. by Elia Batastelli.)
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UBC and ACT
Mandana Amari
Elia Batastelli
Bryce Burger
Matthew Hasselfield
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Cross Linked Scan Strategy is Crucial to Making Maps on Degree Angular Scales
• 240 square degrees in circle• 100 square degrees for CMB
QuickTime™ and aBMP decompressor
are needed to see this picture.
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An image of Jupiter taken in drift scan with an 8x32 camera, taken before primary surface alignment, in fact taken before the ladder was removed from in front of the primary!
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observing• 2007 Season Complete: 30 Days with 1000-element 145 GHz detector array
• 2008 Season to commence in June for 6 months with 145, 215, (and 280) GHz arrays
• 2009 Season: Another 6 months with three arrays
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Bullet cluster SZ
Previous Generation SZACT
-55.8
-55.9
-56.0
-56.1
104.875 104.75 104.625 104.5
ACT Inset
Gomez et al. 2003Black contours are show dark matter distribution
derived from weak lensing and brown contours show gas distribution derived from X-rays. (Clowe et al. 2006)
2007 Data
6 minutes effective observing time..0.03% of our data
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Thank You!
Photo by Elia Batastelli, 7 Oct. 2007.
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800 lbs
General relation of MBAC to ACT TelescopeScanning is performed by rotating the entire structure about a vertical axis passing through the cryostat.
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WMAP-3yr (Black)
WMAP-1 yr (Grey)
Cosmic Variance
The TT power spectrum is now cosmic-variance limited out to l =400.
Notice how little difference there is l by l between 1-year and 3-year data.
The sharp “snake bites” at l=180 and 205 are slightly smaller, but still present.
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Pulse Tube4He Fridge
3He Fridge
40K Shield
3K Shield
Window
3 feet
Detectors
Cylindrically shaped aligned along optical axis
Liquid-Cryogen Free Pulse Tube Coolers 1st stage: 80W @ 45K expected: 30W @ 40K
2nd stage: 2W @ 4.2K expected: 0.2W @ 3K
Helium-4 and Helium-3Sorption Fridges 270 mK temp w/ 60 hour hold time with 15 μW load
MBAC Layout
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Regions of the Sky covered
BCS
GALEX, XRAY
The bands are the areas Of sky we observe in CMB
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Secondary Mirror
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Turnoff from Jama Road
APEX
ACT
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ACT –5200 meters
APEX ALMA SupportDevlin
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