2. The Cosmic Background Imager - a status report -
Steven T. Myers
National Radio Astronomy Observatory
Socorro, NM

3. The Instrument 13 90-cm Cassegrain antennas 6-meter platform
78 baselines
6-meter platform
Baselines 1m – 5.51m
10 1 GHz channels 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

4. CMB Interferometer – The CBI
The Cosmic Background Imager (CBI)
13 elements, 90 cm antennas, GHz (10 channels)
fixed to 3-axis platform  telescope rotation synthesis!

5. 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; yrs; 2004 pol
2002 continued NSF funding to end of 2004
exploring funding prospects to operate until 2006 and beyond

6. Site – Northern Chilean Andes

7. Site – Northern Chilean Andes
CBI site seen from above

8. CBI in Chile

9. CBI in Chile

10. CBI in Chile

11. CBI Instrumentation

12. CBI Polarization Program
Observed September 2002 to April 2005
compact configuration, maximum sensitivity

13. 2002 CBI Upgrade: New NRAO HEMTs
New TRW InP HEMTs from NRAO

14. Ground Signal Ground emission (polarized) removal
Strong on shortest baselines (100l)
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 polarization observations
ground screen scheduled for construction in late 2005 (Oxford)

15. Before ground subtraction:
I, Q, U dirty mosaic images:

16. After ground subtraction:
I, Q, U dirty mosaic images (9m differences):

17. 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

18. galactic projection – image WMAP “synchrotron” (Bennett et al. 2003)
CBI & DASI Fields
galactic projection – image WMAP “synchrotron” (Bennett et al. 2003)

19. CBI Beam and uv coverage
primary beam transform:
θpri= 45' Δl ≈ 4D/λ ≈ 360
mosaic beam transform:
θmos= n×45' Δl ≈ 4D/nλ
Over-sampled uv-plane
excellent PSF
allows fast gridded method (Myers et al. 2000)

20. 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±1.8mK2

21. NEW RESULTS! CBI 2004 vs. 2005
All data from Sep 2002 – Apr 2005: 54% more than in Readhead et al. 2004
Red o’s – 2004
Blue x’s
Black Line
new best fit
Magenta Line
old WMAP
+CBI+ACBAR
Black *’s – old
predicted #’s.
2 vs. model:
(7 dof each)
TT: 10.4
EE:
BB:
TE:
astro-ph/

22. Combine CBI05, DASI, B03

23. polarization peaks aligned w/TT
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:
polarization peaks aligned w/TT

24. NEW: Isocurvature CBI Pol – green All Pol – brown CBI+B03 - grey
Note – strongest constraints from TT
 few parameters are better constrained in polarization

25. 20h strip: gridded FT( E + i B) uv-plane, transform to image
NEW: E & B Mode Images
20h 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 raw
data 2.45 times B
(ℓ<1000). B is
consistent with
noise.
Mixing between E,B
Is ~5% in power.

26. ℓ -space CLEAN deconvolved!
ℓ-space maps
use gridded visibilities to reconstruct T,E,B in ℓ-space
02h 6x6 field mosaic
T image  ℓ Tℓ
ℓ -space CLEAN deconvolved!

27. ℓ-space maps use gridded visibilities to reconstruct T,E,B in ℓ-space
sub-Nyquist mosaic pattern  “sidelobes” in ℓ-space
linear filtered reconstruction: B R-1 D

28. CBI Projections
Will BB (lensing) be foreground limited?

29. CBI SZE

30. The CBI SZE Sample f 0.1-2.4keV > 1.0 x 10-11 erg cm-2 sec-1
L keV > 1.13 x 1044 h-2 erg s-1
declination –70° < d < 24 °
24 clusters accessible to CBI
primary sample 15 most luminous
sample covers range of cluster types
detailed in Udomprasert et al. (2004) ApJ
A85, A399, A401, A478, A754, A1651, A2597

31. CBI SZE visibility function
Xray: θ-3 (b ~ 2/3)
SZE: θ-1 → -exp(-v)
dominated by shortest baselines

32. Udomprasert et al. (2004) ApJ 615 63
CBI: A478
(left) Raw CBI Image (center) CLEAN source-sub CBI Image (right) CBI w/ROSAT
differenced lead-main-trail 8m separation
A478 – relaxed cooling flow cluster, X-ray cavities from AGN
Udomprasert et al. (2004) ApJ

33. CBI: A478 A478 – relaxed cooling flow cluster, X-ray cavities from AGN
Chandra: Sun et al. astro-ph/ (inner region GHz radio)
(left) Raw CBI Image (center) CLEAN source-sub CBI Image (right) CBI w/ROSAT
A478 – relaxed cooling flow cluster, X-ray cavities from AGN

34. NEW: CBI A3667 combined Nov00 + Jul05 extended + compact configs.
Kassandra Wells (Carleton) summer student project

35. 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!

36. CBI Future CBI Beyond CBI  QUIET Beyond QUIET?
stopped polarization observing in April 2005
some foreground & SZ observations in summer 2005
2005: Oxford joins CBI collaboration
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

37. Imaging the SZE with ALMA Band 1
ALMA observes SZE
SZE simulation (left) hours ALMA (center) after 4kl taper (right)
2.5 × 1014 Msun z= GHz in compact config equiv. 22” FWHM
~5σ SZA survey detection mJy (14 mK) 9.7” beam mJy (2.7 mK)
ALMA will provide images of high redshift clusters identified in surveys from other instruments like AMI, SZA, SPT, APEX-SZ, ACT

38. Galactic center at 30 GHz in I,Q,U

39. The CBI Collaboration
Caltech 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.