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Mark Devlin – University of PennsylvaniaFor the ACT Collaboration

Probing Fundamental Physics Through Measurements of Cosmic Structure

ACT: The Atacama Cosmology Telescope

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ACT SiteALMA

PolarBearACT

(CLASS)

• 5200 m• Latitude -23o

• 0.5 mm PWV -> 150GHz = 0.02

ACT Site

Generators

15,000 liter Diesel Tank

High bay and Workshop

ABSSupplies

Control and Equipment Room

Telescope

Radio Linkto San Pedro

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ACT Optics

4

6m

400 kg

1.3 arcmin at 150 GHz

2m

ACTPolOMT TES

Silicon arrays

Feedhorn array

• 3 Optics Tubes• 1 deg FOV• 80 mK DR• 100 µW

1.8 m

30cm

A typical SZE observation with ACT• ACT has 1.3’ resolution at 148 GHz.• ACT images are typically smoothed to 2.4’ for 

display purposes (see Hincks et al. 2010).

Hincks et al. 2010

ACT taken by the light of a full Moon(30 second exposure)

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ACT Results2013• Cosmological parameters from three seasons of data

Sievers et al.• Sunyaev-Zel'dovich Selected Galaxy Clusters at 148 GHz

Hasselfield et al.• The stellar content of galaxy clusters selected using the Sunyaev-Zel'dovich effect

Hilton et al.• Likelihood for small-scale CMB data - Dunkley et al.

2012• Evidence of Galaxy Cluster Motions with the Kinematic Sunyaev-Zel'dovich Effect

Hand et al. - PHYSICS WORLD “Top Ten” Breakthrough for 2012• The Atacama Cosmology Telescope: ACT-CL J0102-4915 "El Gordo,"

a Massive Merging Cluster at Redshift 0.87Menanteau et al. – DISCOVER Magazine #64 Science News 2012

2011• Detection of the Power Spectrum of Cosmic Microwave Background Lensing

Das et al. - PHYSICS TODAY Top Search and Discovery result of 2011

El Gordo

• 11 Sept 2013 – 24 Dec 2013 (500 hrs)• One 150 GHz array installed• Four ~ 70 deg2 patches• Overlap with other surveys for cross-correlation

ACTPol First Season Observations(Naess et al, JCAP(2014))

• One of the 4 ACTPol fields: D6• (Area ~ 60 deg2)

ACTPol First Season Observations(Naess et al, JCAP(2014))

Circa – Just before this meeting(November 2014)

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• BICEP2• ACTPol hi-res data• Planck data read off plots • POLARBEAR & ACTPol are

direct BB• SPT & “preliminary”

ACTPol are indirect lensing BB

Compilation by L. Page

We detect halo lensing from 12,000 stacked CMASS galaxies at S/N of 3.2 sigma

Best-fit of M200 = 2.0+-1.0 1013 Msolar and C200 = 5.4+-0.8

● Excess seen in all three observing regions

● Signal consistent with Optical Weak Lensing measurement from Miyatakeet. al. 2013

Thermal SZ One-Point PDF at 148 GHzHill et al. (2014) arXiv:1411.8004 — see poster session!

tSZ decrements

148 GHz Tfilt

BinnedHistogram(negative Tfilt only)

• Simple observable: histogram of pixel temperature values• Use info from all clusters in the map, including SNR<5• Optimal one-halo term tSZ statistic: very sensitive to σ8

• Build on earlier ACT tSZ skewness measurement (Wilson++ 2012)

Thermal SZ One-Point PDF at 148 GHzHill et al. (2014) arXiv:1411.8004 — see poster session!

σ8

likelihood

~2x smaller than stat. error from tSZ skewness alone (Wilson++12)

Errors assume 3 seasons of AdvACTPol observations

• Cosmic variance‐limited EE measurement out to ell=2000

• 5x better resolution than Planck with 5x the Plancksensitivity

• 3x more polarization modes than Planck

• New constraints on the CDM cosmology

Advanced ACTPol (AdvACT)

Complete overlap with DES, LSST & DESI survey regions

AdvACT Survey Plans

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South Pole

ChileD56

BOSS

D7

BICEP2

r=1r=0.01

Planck Foreground Level in Effective r

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AdvACT Specifications

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Detector Array Center[GHz]

Width [GHz]

# TES NETCMB[ ]

Map Noisearcmin]

Beamarcmin

Low Frequency (LF) 28 6 80 35 78 7.1

Low Frequency (LF) 41 19 80 32 71 4.8

Medium Frequency (MF) 90 38.5 1760 5.8 7.8 2.2

MF/HF 150 41 2816 5.4 6.9 1.3

High Frequency (HF) 230 100 1056 20 25 0.9

20,000 deg2

Half the sky ‐> r=0.01 at 3‐4 ‐> Subdivide to check isotropy

detector passbands

Advanced ACTPol (AdvACT)

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• New dichroic polarimeters

• Datta et al., JLTP (2014)

• Array to be deployed on ACT in Jan 2015

Detector wafer

Horn array

Assembled Array

Rotating HWP Provides Stability

• 2Hz rotation ‐> • 8 Hz Modulation ‐>• 800 sec Stability!

Three 30 cm HWPs installed directly in front of the AdvACT receiver

AdvACT Will Test Large‐Field Inflation

Can detect r = 0.01 signal

• Can clean synch and dust• Cleaned maps at both 90 

and 150• Can confirm signal is 

isotropic and that result is independent of foregrounds

• Measure B mode spectrum

Advanced ACTPol (AdvACT)

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Projected to improve Planck limit on m

Projected to improve LSST’s DE FOM by 20x!

Big Telescope for Big B‐Modes

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Antarctica December 2010

BLAST‐Pol 500 μm Inferred B‐Field 

Direction in Vela C

Background image: 500 μm polarized intensityContours: 500 μm Total Intensity

4400 Nyquist sampled vectors when smoothed to 2.5 arcmin resolution

Coming Soon – BLAST-TNG

• 2.5 meter Carbon Fiber Mirror• 2200 detectors at 250, 350 and 500 m• 22 arcsec resolution at 250 m• 16 times the speed of BLAST-Pol

• First flight December 2016 with Shared Risk Observing

THE END

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