Cosmology with ACT

Photo of the Atacama Cosmology Telescope by Michele Limon

Mark Halpern, UBC

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

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?

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.

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.

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

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°

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.

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.

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

Photo by Michele Limon

The ground screen under construction at Cerro Toco.

A view looking down the face of the primary, before the panels were installed

Panels Installed

Each panel of the primary mirror is adjusted by hand and locked in place.

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.

Photo: Mike Neimack

The ACT 145 GHz array, fully assembled.

• 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

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.)

UBC and ACT

Mandana Amari

Elia Batastelli

Bryce Burger

Matthew Hasselfield

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.

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!

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

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

Thank You!

Photo by Elia Batastelli, 7 Oct. 2007.

800 lbs

General relation of MBAC to ACT TelescopeScanning is performed by rotating the entire structure about a vertical axis passing through the cryostat.

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.

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

Regions of the Sky covered

BCS

GALEX, XRAY

The bands are the areas Of sky we observe in CMB

Secondary Mirror

Turnoff from Jama Road

APEX

ACT

ACT –5200 meters

APEX ALMA SupportDevlin