The Cosmic Background Imager - a status report -

2The Cosmic Background Imager – Amiba Mini-workshop, 25 Sep 2005

The Cosmic Background Imager

- a status report -Steven T. Myers

National Radio Astronomy Observatory

Socorro, NM


The Instrument

• 13 90-cm Cassegrain antennas– 78 baselines

• 6-meter platform– Baselines 1m – 5.51m

• 10 1 GHz channels 26-36 GHz– HEMT amplifiers (NRAO)

– Cryogenic 6K, Tsys 20 K

• Single polarization (R or L)– Polarizers from U. Chicago

– < 2% leakage

• Analog correlators– 780 complex correlators

• Field-of-view 44 arcmin– Image noise 4 mJy/bm 900s

• Resolution 4.5 – 10 arcmin


CMB Interferometer – The CBI• The Cosmic Background Imager (CBI)

– 13 elements, 90 cm antennas, 26-36 GHz (10 channels)– fixed to 3-axis platform telescope rotation synthesis!


CBI milestones• 1980’s

– 1984 OVRO 40m single-dish work (20 GHz maser Rx!)– 1987 genesis of idea for CMB interferometer

• 1990’s– 1992 OVRO systems converted to HEMTs– 1994 NSF proposal (funded 1995)– 1998 assembled and tested at Caltech– 1999 August shipped to Chile– 1999 November Chile first “light”

• 2000+– 2000 January routine observing begins– 2001 first paper; 2002 first year results; 2003 2yrs; 2004 pol– 2002 continued NSF funding to end of 2004– exploring funding prospects to operate until 2006 and beyond


Site – Northern Chilean Andes


Site – Northern Chilean Andes

CBI site seen from aboveCBI site seen from above


CBI in Chile


CBI Instrumentation


CBI Polarization Program

• Observed September 2002 to April 2005– compact configuration, maximum sensitivity


2002 CBI Upgrade: New NRAO HEMTs

• 2002 Upgrade– New TRW InP HEMTs from NRAO

Ka-band Receiver

0

2

4

6

8

10

12

14

16

18

20

26 28 30 32 34 36 38 40

Frequency (GHz)

No

ise

Tem

per

atu

re (

K)


Ground Signal• Ground emission (polarized) removal

– Strong on shortest baselines (100)– Depends on orientation – AZ/EL & time dependent– Differencing between lead/trail field pairs (8m in RA=2°)

• Use 6-pt x 3m RA scanning for 2002-2003 polarization observations

• ground screen scheduled for construction in late 2005 (Oxford)


Before ground subtraction:

• I, Q, U dirty mosaic images:


After ground subtraction:

• I, Q, U dirty mosaic images (9m differences):


Foregrounds – Sources

• Foreground radio sources– Located in NVSS at 1.4 GHz,

VLA 8.4 GHz

– project out of power spectrum using constraint matrix

– equivalent to masking in image plane

– 3727 total too many!

• Need 30 GHz measurements– locate positions of brightest

sources in I and P

– soon GBT 30 GHz system


CBI & DASI Fields

galactic projection – image WMAP “synchrotron” (Bennett et al. 2003)


CBI Beam and uv coverage

• Over-sampled uv-plane– excellent PSF– allows fast gridded method (Myers et al. 2000)

primary beam transform:primary beam transform:

θθpripri= 45= 45' ' ΔΔll ≈ 4D/ ≈ 4D/λλ ≈ 360 ≈ 360

mosaic beam transform:mosaic beam transform:

θθmosmos= = nn××4545' ' ΔΔll ≈ 4D/ ≈ 4D/nnλλ


NEW RESULTS! CBI Data to 2005…Include data from Sep 2002 – Apr 2005: ~50% more

shaped EE

likelihood vs. zero : 10.1 σ

BB 1.2±1.8K2


NEW RESULTS! CBI 2004 vs. 2005All data from Sep 2002 – Apr 2005: 54% more than in Readhead et al. 2004

Red o’s – 2004Blue x’s - 2005Black Line new best fit Magenta Line old WMAP +CBI+ACBARBlack *’s – old predicted #’s.

2 vs. model: (7 dof each) TT: 10.4 EE: 1.3 BB: 5.7 TE: 5.9

astro-ph/0509203


Combine CBI05, DASI, B03


NEW: Isocurvature

• Are there curvature fluctuations?– if standard model then

matter/photon ratio preserved (adiabatic)

– some inflation (or other) models predict isocurvature modes

• matter & radiation anti-correlated, acoustic peaks not shifted

isocurvature mode:isocurvature mode:polarization peaks aligned w/TTpolarization peaks aligned w/TT


NEW: Isocurvature

CBI Pol – green

All Pol – brown

CBI+B03 - grey

Note – strongest constraints from TT few parameters are better constrained in polarization


NEW: E & B Mode Images20h strip: gridded FT( E + i B) uv-plane, transform to image

Grid visibilities into ℓ-space estimators (e.g. Myers et al. 2003).

Variance of E in rawdata 2.45 times B(ℓ<1000). B isconsistent with noise.

Mixing between E,BIs ~5% in power.


ℓ-space maps

• use gridded visibilities to reconstruct T,E,B in ℓ-space

T image ℓ Tℓ

ℓ -space CLEAN deconvolved!

02h 6x6 field mosaic


ℓ-space mapsuse gridded visibilities to reconstruct T,E,B in ℓ-space

linear filtered reconstruction: B R-1 sub-Nyquist mosaic pattern

“sidelobes” in ℓ-space


CBI Projections

• Will BB (lensing) be foreground limited?


CBI SZE


The CBI SZE Sample

• f 0.1-2.4keV > 1.0 x 10-11 erg cm-2 sec-1

• z < 0.1

• L 0.1-2.4keV > 1.13 x 1044 h-2 erg s-1

• declination –70° < < 24 °

• 24 clusters accessible to CBI

• primary sample 15 most luminous

• sample covers range of cluster types

• detailed in Udomprasert et al. (2004) ApJ 615 63

A85, A399, A401, A478, A754,

A1651, A2597


CBI SZE visibility function

• Xray: θ-3 ( ~ 2/3)• SZE: θ-1 → -exp(-v)• dominated by shortest

baselines


CBI: A478

• A478 – relaxed cooling flow cluster, X-ray cavities from AGN

(left) Raw CBI Image (center) CLEAN source-sub CBI Image (right) CBI w/ROSAT

Udomprasert et al. (2004) ApJ 615 63

differenced lead-main-trail 8m separation


CBI: A478

• A478 – relaxed cooling flow cluster, X-ray cavities from AGN

(left) Raw CBI Image (center) CLEAN source-sub CBI Image (right) CBI w/ROSAT

Chandra: Sun et al. astro-ph/0210054 (inner region + 1.4 GHz radio)


NEW: CBI A3667

• combined Nov00 + Jul05• extended + compact configs.• Kassandra Wells (Carleton)

summer student project


A3667 Xray• XMM observations:

Briel et al. 2004• I, T, S, P maps• Nearby clusters ideal

for study of IGM astrophysics and substructure

• While Chandra & XMM are operational!


CBI Future• CBI

– stopped polarization observing in April 2005• some foreground & SZ observations in summer 2005

– 2005: Oxford joins CBI collaboration • 2005-2006 add ground screen• chase after high-ell excess

– 2006: CBI becomes testbed for QUIET

• Beyond CBI QUIET– detectors are near quantum & bandwidth limit – need more!

– but: need clean polarization (low stable instrumental effects)• polarization B-modes! (at least the lensing signal)

– large format (1000 els.) coherent (MMIC) detector array

• Beyond QUIET?– CMB polarization mega-interferometer?

• use new technology for mega-correlators


Imaging the SZE with ALMA Band 1

ALMA observes SZE

SZE simulation (left) 4 hours ALMA (center) after 4k taper (right)

2.5 × 1014 Msun z=1 34 GHz in compact config. equiv. 22” FWHM

~5σ SZA survey detection 1.5 Jy (14 K) 9.7” beam 2.8 Jy (2.7 K)

ALMA will provide images of high redshift clusters identified in surveys from other instruments like AMI, SZA, SPT, APEX-SZ, ACT


Galactic center at 30 GHz in I,Q,U

Galactic center at 30 GHz in I,Q,U


The CBI CollaborationCaltech Team: Tony Readhead (Principal Investigator), John Cartwright, Alison Farmer, Russ Keeney, Brian Mason, Steve Miller, Steve Padin (Project Scientist), Tim Pearson, Walter Schaal, Martin Shepherd, Jonathan Sievers, Pat Udomprasert, John Yamasaki.Operations in Chile: Pablo Altamirano, Ricardo Bustos, Cristobal Achermann, Tomislav Vucina, Juan Pablo Jacob, José Cortes, Wilson Araya.Collaborators: Dick Bond (CITA), Leonardo Bronfman (University of Chile), John Carlstrom (University of Chicago), Simon Casassus (University of Chile), Carlo Contaldi (CITA/ICL), Nils Halverson (University of California, Berkeley), Bill Holzapfel (University of California, Berkeley), Marshall Joy (NASA's Marshall Space Flight Center), John Kovac (University of Chicago), Erik Leitch (University of Chicago), Jorge May (University of Chile), Steven Myers (National Radio Astronomy Observatory), Angel Otarola (European Southern Observatory), Ue-Li Pen (CITA), Dmitry Pogosyan (University of Alberta), Simon Prunet (Institut d'Astrophysique de Paris), Clem Pryke (University of Chicago).2005 – Oxford joins CBI! Mike Jones, Angela Taylor, Pedro Ferreira, Jo Dunkley, Steve Rawlings

The CBI Project is a collaboration between the California Institute of Technology, the Canadian Institute for Theoretical Astrophysics, the National Radio Astronomy Observatory, the University of Chicago, and the Universidad de Chile. The project has been supported by funds from the National Science Foundation, the California Institute of Technology, Maxine and Ronald Linde, Cecil and Sally Drinkward, Barbara and Stanley Rawn Jr., the Kavli Institute,and the Canadian Institute for Advanced Research.

The Cosmic Background Imager - a status report -

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