Acbar and the South Pole Telescope: Small angular scale CMB and cluster cosmology

John Ruhl, [email protected]

Amundsen-Scott South Pole Station

Why the South Pole? Dry air.

L2

Atmospheric stability:

860 GHz Zenith Optical Depth J.B. Peterson et al. 2002

The ACBAR Collaboration U.C. Berkeley:

Case Western:

Caltech:

W.L. Holzapfel M.D. Daub C.L. Kuo M. Lueker D. Woolsey

J. Ruhl J. Goldstein Z. Staniszewski

A.E. Lange C. Reichardt M.C. Runyan

Cardiff: LBL: C. Cantalupo

CITA: J.R. Bond C.R. Contaldi D. Pogosyan

Winterovers: Matt Newcomb (2001,2002) Paolo Calisse (2003) Justus Brevik (2004) Jessica Dempsey (2005)

P.A.R. Ade C.V. Haynes C. Tucker

CMU: P. Gomez J.B. Peterson A.K. Romer

JPL: J.J. Bock A.D. Turner

Funded by the NSF Office of Polar Programs

Acbar+Viper

Acbar: A 250mK, 16 element mm-wave bolometer array

Viper : An off-axis 2 (+1) m diameter telescope

2+1=3 0.5 meter radius “guard ring” 2 meter diameter primary

Cold stuff 3He/3He/4He

Feed Horns

Fridge Filters

FETs (120K)

240mK Detectors

Bands vs. Cosmic Signals Band Width

CMB

150 20% 219

SZ

15% 274 18%

Bands vs. Atmospheric Transmission Band Width

150 20% 219 15% 274 18%

Measured Performance of ACBAR (2002 Season)

Frequency Band (GHz) Bandwidth (GHz) Number of Detectors Optimal efficiency (%) Beam Size (FWHM) Detector NEP (10-17 W/!Hz) NETRJ (µK !s) (1 detector) NETCMB (µK !s) (1 detector)

150 31 8 40 4.7 9.4 200 350

220 31 4 34 4.2 9.5 250 770

280 48 4 33 3.9 14.8 280 1550

Money channel Sensitivity/sqrt(t_obs) at 150GHz comparable to Boomerang (on a balloon)!

Chopper, calibration monitor

moves beams “horizontally” on the sky. ("2.2° rotation for 1° movement on sky)

Baffle Calibrator Lamp

Scan Strategy Chopping flat rotates to sweep the array “horizontally” by 3 deg on the sky (triangle wave, 0.7 and 0.3 Hz used)

LMT analysis: While tracking (to compensate for Earth rotation), integrate for 30 seconds on “lead” # L 60 seconds on “main” # M 30 seconds on “trail” # T 30s Lead

60s Main

30s Trail

To remove stationary and linearly drifting chopped offsets, our first CMB analysis was done on the pseudo-map:

S = M – (L + T)/2

2001 & 2002 CMB sky coverage 150 GHz Dust Model CMB5 CMB7

CMB2

CMB6

Each field is ~18 deg2. (Finkbeiner, Davis, & Schlegel, 1999)

Point source provides monitor of pointing and beams: Coadded point source image includes beam size and pointing jitter.

FIELD (PMN object) RA (J2000) DEC Time (d) s150/beam CMB2 (J0455-4616) 73.962 -46.266 39 ~9µK CMB5 (J0253-5441) CMB6 (J0210-5101) CMB7 (J2235-4835)

43.372 32.692 338.805

-54.698 -51.017 -48.600

109 23 21

~5µK — —

First Result (2001/2002 data, submitted to ApJ December 2002, published 2004) 150 GHz data only

10% calibration uncertainty

l

Weight = sum(1/sigma^2) = 0.00054 uK^4

Excess at high ell?

CBI’s “SZ excess” scaled to 150 GHz

SZ Clusters

1. Hot electrons in the ICM distort the CMB. 2. Large cluster => 1% of photons up-scattered. 3. CMB distortion => surface brightness is z independent

dT_sz / dT_cmb $

SZ sources are roughly twice as strong in CBI’s CMB maps, and therefore about 4 times stronger in power spectra (uK^2)

SPT

SPT

SPT

SPT

Two paths to better high-ell measurements 1. Optimize the analysis for high-ell (no more LMT subtraction). Expect improvement of about 8/3 in S/N. 2. Take much more good data. (Didn’t happen until 2005)

No LMT Analysis (submitted in 2006, published in 2007) As expected, about a factor of 2 improvement for ell>1000

10% calibration uncertainty

Weight = sum(1/sigma^2) = 0.0024 uK^4

More data: All 150’s in 2005 Frequency band (GHz)

Year

150

220

280

325

2001

4

4

4

4

2002

8

4

4

0

2004

8

4

4

0

2005

16

0

0

0

Money channel. (In 2003 another instrument was on the telescope, doing sub-mm galactic polarization measurements)

Faster chop => microphonics; LHe ran out early

Sky Coverage larger fields in 2005 used to connect calibration to WMAP

Acbar’s Final Power spectrum Narrower bands and smaller errors on each…

2.2% calibration uncertainty

Weight = sum(1/sigma^2) = 0.012 uK^4

Acbar + Boomerang + WMAP

Lambda-CDM works great to ell=2000; hint of maybe an excess from there?

Parameters: From WMAP3 base, adding Acbar, or Acbar +others, pushes a few parameters around at about 2x1014 Msolar. Expect about 20,000 of them.

2. Measure high-l CMB power spectrum very well, to improve limits on ns, %8, etc. 3. Measure CMB B-mode polarization anisotropies all the way down to l = 50. => • Measure primordial gravity waves from inflation • Get neutrino mass from lensing B-modes

SPT’s “CMB/SZ zone”

Features: • Typical cluster sizes ~few arcminutes. • Total SZ proportional to temperature weighted mass (pressure). • Surface brightness is redshift independent. • Size of effect < 1mK Challenges: • Uncertainty in mass-SZ relation (address with self-calibration = using other info in the dataset: z distribution, cluster clustering, SZE luminosity(z) function.)

• Survey completeness/contamination: • primary CMB anisotropy,

• radio galaxies, Address w/ multi-freq. obs. • dusty galaxies, • projection effects/confusion

Should be small… 0.25% ?

N(M,Z) depends on volume and growth factors (as well as other cosmological params) => sensitive to a(t)

Simulation: 3 degrees at 90GHz CMB + SZ (no noise, no point sources)

Carlstrom, Holder, Reese Ann. Rev. Astron. Astrophys. 40:643-680, 2002

SZ Clusters

dN/dz

z=1

z=2

z=3

dN/dz for SPT

Counts per &z = 0.01

(proposal prediction)

4000 sq.deg survey

Figure: G. Holder

Redshift (z) (requires optical followup)

Mass histograms The “mass histogram” evolves as f(z)… which means that N(M,z) can be used to test for consistency with simulations (and whether Mass(SZ) is understood well enough!)

z=0.1

Number Density z=1

Mass

Redshifts via optical followup 1. BCS: “mini-survey” with MOSAIC camera on Blanco 4m (~100 deg2). griz bands. Good to about z=1. Most of the data is in the can. 2. SMI (Simultaneous Multiband Imager) on Magellan 6.5m (griz follow up ~2500 clusters in 30 nights) 3. DES (new camera) on Blanco 4m: complete optical coverage of SPT survey region, to about z=1.3, w/ delta_z about 0.02. Also gives shear maps around clusters => another mass estimate.

The Dark Energy Survey Fermilab, UIUC, U.Chicago, LBL, Argonne, NOAO, NCSA, U.Mich, U.Penn, ANL, OSU, Spain, UK, Brazil

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A study of the dark energy using four independent and complementary techniques – – – –

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Blanco 4m on Cerro Tololo

Galaxy cluster surveys Weak lensing Galaxy angular power spectrum SN Ia distances

Two linked, multiband optical surveys – 5000 deg2 g’, r’, i’ and z’ – Repeated observations of 40 deg2

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Instrument and schedule – New 3 deg2 camera on the Blanco 4m on Cerro Tololo – Construction: 2004-2010 – Survey Operations: 2010 -

Image credit: Roger Smith/NOAO/AURA/NSF

Predicted constraints on 'm , 'DE and w (assuming redshifts from DES, 100 followup mass measurements, and self-calibration analysis) Contours are 68% C.L.

Figure from the SPT white paper for the Dark Energy Task

Science Goal #2: Secondary CMB Acbar’s limit per bin, about 1e-9 K^2

1. Measure the SZ power spectrum after removing obvious clusters… 2. Measure CMB-spectrum power spectrum at high l after removing thermal SZ signal… requires multiple colors (or 220GHz).

500 sq. deg. surveys, Noise is on CMB-only after perfect tSZ subtraction.

Figure: T. Crawford, spectra from W. Hu

Science Goal #3: CMB polarization From Hu & Dodelson, Ann. Reviews 2002

Errors shown are for Planck...

Lensing B-modes (a way to map the dark matter) Primordial B-modes, fingerprint of Inflation. (Shown for T/S = 0.1, a high value)

Design and Pictures

10m diameter primary

SPT optics

250mK focal plane array

10K, 1m diameter secondary

Structure and Shielding 144’ across

Occultation limit: 28°

47’ high

Inner Shield (moves) Outer Shield (fixed)

To DSL

SPT optics cryostat

SPT optics cryostat (10K secondary in vacuum shell, summer 2006)

Optics Baffles (summer 2006)

Baffles and secondary installed (August 2006)

Receiver on optics cryostat (below telescope)

SZ Focal Plane design conical feedhorns above bolometers, 960 elements

Horn array plate

Bolometers Figure: W. Holzapfel

2007 focal plane in dewar (from frontside)

160 Bolometer wedge (fits in 4” diameter wafer)

January 2007

February 2007

Winter

DATA (so far) > 20 Tb of data so far…. (and expect another 20Tb/season from now on)

Winter 2007 data •

Detector sensitivities were poor due to fabrication issues, but nonetheless there will be some interesting science output.

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Two sub regions of the Blanco Cosmology Survey 5.5hr field (which overlaps Boomerang deep field, which was also covered by Acbar) – Large field ~35 deg2 • 300 hours integration time • Cluster discovering • Sensitivity should be ~ 40 uK / arcmin2 – Small field ~6 deg2 • Located inside the large field • 200 hours integration time • small scale (high l cmb) to ~ 20 uK / arcmin2

• Processing is still very “young”… but coming together quickly.

Known clusters, 2008 data AS1063

Bullet Cluster

3 hour observation, 150GHz (scale is n-sigma) 40 Minutes observation 150 GHz

SPT “future” 2008: Observing at 90, 150, 220GHz. Currently going deep (about 15uK/beam now) on a 100 sq deg field. More sky after that. (Note: Poor yield at 90GHz this year, so really it’s 150+220).

2009, 2010: More SZ observations (unpolarized). (Improve detector yields)

2011: Install polarimeter.

END

Very preliminary, “naiive”, 2007 small field maps (also, poor pointing reconstruction)

Telescope

Drive components are all in warm environment

Receiver cabin docks to control room for access

Observing Strategy: Atmospheric Noise and Filtering (no chopper… can we succeed with telescope-scanning?) Input: • celestial signals (CMB, SZ) • detector noise (with 1/f) • Acbar-normalized atmospheric fluctuations • SPT scan rate Process: • Do “fake” array observation to create timestream, • use some method to filter 1/f + atmospheric noise Output: • naïvely “binned” maps • cluster mass detection thresholds, etc

Pure Timestream filtering 3°x 3°

Noise: • 0.1 Hz 1/f • “SP-Acbar Atmosphere” Scan rate: 2'/second

Filter: 0.3Hz HP Tom Crawford, U. Chicago

Array common-mode subtraction only 3°x 3°

Noise: • 0.1 Hz 1/f • “SP-Acbar Atmosphere” Scan rate: 2'/second

Filter: 16 spatial modes at each timestep

Tom Crawford, U. Chicago

Band selection: which of 90, 150, 220, 270, 345 GHz ? CMB

150 + 220 GHz

Thermal SZ IR point sources

270 GHz

Radio point sources

90 GHz ? (but resolution gets worse…)

Expected performance of these bands if used on the SPT (trans)

Optical Design: Off-axis Gregorian Parabolic Primary (f/0.7)

focal plane Elliptical Secondary

lens

Note: no chopper.

S. Padin

10 Kelvin Secondary and Baffle 4 K plastic 300mK

300mK

10 K black

10 K

Pointing budget

Acbar skydips determine atmospheric opacity… (and soon, Bussman etal 2004, atmospheric noise properties in Acbar’s bands…)

(SP summer)

How to measure w? Parameterize dynamics of Dark Energy as:

Where

In a Dark Energy-dominated Universe, the scale factor evolves as:

How can we trace recent expansion history? Number counts vs. redshift of a nonevolving species give you physical volume per unit solid angle per unit redshift.

“Luminosity distance”,

“Angular diameter distance”

Line element vs. redshift

How can we trace recent expansion history? But physical number density of clusters does evolve, luckily in a cosmologydependent manner. Growth of linear perturbations is very sensitive to expansion.

e.g., Peebles 1980 And clusters are highest peaks in density field

Observing/Analysis Challenges •

Mass/Observable relation

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Due to steepness of mass function, we have to know this distribution well. (10%? 20%?) –

The more interesting the distribution, the better we have to know it. (Long tails are bad.)

Observing/Analysis Challenges •

Contributions to the interestingness of Mass/Observable relation

1. Intrinsic scatter in SZ flux vs. mass. • Integrated SZ is total thermal energy in cluster – should be insensitive to internal dynamics. • Motl et al. show ~5% scatter and no large outliers. 2. Instrument noise & primary CMB. 3. Cluster-cluster confusion. • Unresolved background ~5% for 2d14, sigma8=0.9. • Rare superpositions will be caught by follow-up. 4. Point sources. • “Field” source contribution small and modelable. Motl et al. ApJL 623:63-66 • Cluster-correlated population is an issue.

Observing/Analysis Challenges Cluster-correlated radio sources could cause outliers in . • • • • •

dN/dS measured at Jy levels up to 90 GHz (WMAP) and mJy levels up to 30 GHz (CBI, VSA, etc.). Depending on level of self-absorption, “tired electrons”, etc., powerlaw index of synchrotron spectrum could be anywhere from -2 to +1. Good news: recent follow-up of flat- and inverted-spectrum sources show turnover by 40GHz Bad news: factor of ~20 more sources in clusters than in field – may increase with z. NEED MORE DATA

More data on the way •

SZA is operational. –

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Simultaneous hi-resolution observations (i.e., baselines from point-source monitoring “outrigger” scopes) will measure mJy-level cluster radio source population at 30 GHz in ~100 clusters across wide redshift range. 90 GHz follow-up will nail spectral behavior.

While we’re waiting: observations of radio source population in nearby clusters – –

VLA 4.8-40 GHz ATCA 18 GHz

Summary, Part I • •

Cluster counts can constrain Dark Energy equation of state. SZ searches using large-aperture telescopes and bolometerarray cameras are a good way to get a nearly mass-limited cluster sample out to high redshift.

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The South Pole is a great site for mm-wave astronomy, including SZ. DES will provide redshifts (and lots of other good science). Observational / Analysis issues identified; clear paths to overcoming them.

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Telescope Design Goals 1. Angular resolution for clusters (~ 1') at 150 GHz: ! 2. Observe CMB & foregrounds from 1-3mm ! rms < 1mm/100 = 10 microns on small scales, ! !

rms < 1mm/20 = 50 microns on large scales pointing reconstruction ~ 1 arcsecond rms

3. Surveys $ 1° diameter field of view at 150 GHz 4. Low offsets, low loading, low sidelobes ! fixed Gregorian w/ cold secondary and stop, !

2 levels of ground shields.

5. Capable of sub-mm observations in the future ! rms < 20 microns overall (in future) 6. Flexibility for future use ! pure parabolic primary, large optics cabin

Bolometer arrays for SZ observation, present and future • • • • •

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Bolocam and Bolocam-2 – ~150 elements, semiconductor bolometers Penn/NRAO GBT Array – 8x8 TES pop-up array on 100m telescope APEX-SZ – UCB/LBL camera on 12m dish in Chile. ACT – 3-by-1000-element TES pop-up array on 6-meter dish SPT – UCB/LBL/Chicago/CWRU/UIUC/CfA – 1000-element TES horn-coupled array CCAT?

The Facility and Site

Moon Door

Existing Dark Sector Laboratory