Cosmology with ACT. Mark Halpern, UBC. Photo of the Atacama Cosmology Telescope by Michele Limon. A tacama C osmology T elescope. A program designed to measure the high- l features of the CMB.
Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.
Mark Halpern, UBC
Photo of the Atacama Cosmology Telescope by Michele Limon
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
Small scale anisotropy
Polarization at all angular scales
Better known parameters
Non-adiabatic modes ?
Formation and growth of cosmic structure.
Tests of field theories at 10-35 s.
Tilt of the Angular Power Spectrum.
The overall tilt of the spectrum--- encoded in the “scalar spectral index” ns--- is a new handle on inflation.
ACT and other small scale measurements will resolve ns.
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.
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.
Sunyaev Zeldovich effect from clusters
Gravitational Lensing of the CMB
Vishniac Effect and Kinetic SZ
Foreground point sources
Epoch of cluster formation
Measure mass spectrum
Star formation history
Photo from Act towards llano de Chajnantor by Michele Limon
Hot electron gas imposes a unique spectral signature:
photon number is preserved while photons scatter to higher energy
NO SZ Contribution in Central Band
The frequency spectrum (color) of the anisotropy matches the CMB.
Valageas, Balbi &Silk Astro-ph 0009040
Clusters have formed. Cluster velocity produces signal
Linear Effects: OV
Structure in ne not correlated with bulk v.
From Wayne Hu, Astro-ph 9907103
MBAC on ACT
Statistical uncertainties based on 1 season with best measured noise.
Photo by Michele Limon
Each panel of the primary mirror is adjusted by hand and locked in place.
We build the control and readout electronics for these arrays.
Photo: Mike Neimack
Decreasing heater power
This is 10 kHz readout of a sub-pW optical signal.
(Data collected at UBC on a cryostat in New Jersey. by Elia Batastelli.)
Cross Linked Scan Strategy is Crucial to Making Maps on Degree Angular Scales
6 minutes effective observing time..0.03% of our data
Previous Generation SZ
104.875 104.75 104.625 104.5
Gomez et al. 2003
Black contours are show dark matter distribution
derived from weak lensing and brown contours show
gas distribution derived from X-rays. (Clowe et al. 2006)
Photo by Elia Batastelli, 7 Oct. 2007.
Scanning is performed by rotating the entire structure about a vertical axis passing through the cryostat.
The sharp “snake bites” at l=180 and 205 are slightly smaller, but still present.
Notice how little difference there is l by l between 1-year and 3-year data.
WMAP-1 yr (Grey)
aligned along optical axis
Pulse Tube Coolers
1st stage: 80W @ 45K
expected: 30W @ 40K
2nd stage: 2W @ 4.2K
expected: 0.2W @ 3K
Helium-4 and Helium-3
270 mK temp w/
60 hour hold time
with 15 μW load
The bands are the areas
Of sky we observe in CMB