ACT: The Atacama Cosmology Telescope Probing Fundamental Physics Through Measurements of Cosmic Structure Jack Hughes, Rutgers University for the ACT Team

Toronto Princeton Penn Católica CUNY Columbia Haverford ACT Institutions U Mass Pittsburgh NSF funding began Jan 2004

ACT aims to make a high-resolution (1’), low-noise (1  K) map of the CMB The emergence of structure manifests itself as non-Gaussian features in a map, with both compact and diffuse components. The detail to which these are understood depends directly on the quality of the map. High fidelity maps facilitate direct comparisons to other surveys e.g., PLANCK, IRAS, HST, SIRTF. Allow calibration with WMAP anisotropy.

Cluster (SZ, KSZ X-ray, & optical) Diffuse SZ OV CMB to l~10,000 Lensing Observations: Science: Growth of structure Eqn. of state Neutrino mass Ionization history ACT Optical X-ray Theory Power spectrum

CMB Temperature Power Spectrum WMAP PLANCK  Measure the linear regime and the transition to the non-linear  Overlap with WMAP for calibration ACT (Tegmark and Oliveira-Costa)

Thermal SZ effect Inverse Compton Scattering Spectral Signature ACT Bands bridge SZ null Redshift independent “clean” cluster selection 150GHz SZ Simulation PLANCK 1.4° < 1% of survey area ~2% of high quality area MBAC on ACT (Seljak and Burwell 2000)

Camera

The M illimeter B olometric A rray C amera: 3000 Detectors Tricolor : 145, 215, & 280 GHz 3 independent 32x32 arrays TES PUDs from GSFC PUDs = Pop-Up Devices TES = Transition Edge Sensor Each pixel: ~1 mm x ~1 mm (MBAC) Field of View: 22 arcmin square Bandpasses: GHz Multiplexing readout from NIST + UBC

Detectors and Readout Transition Edge Sensor (TES) bolometers –0.3 K operation –Voltage biased at superconducting transition –Negative electrothermal feedback –Low-T current readout => SQUIDs MoAu TES

Filled Detector Arrays Three 32 x 32 “pop-up” detector arrays (SHARC, HAWC) ½ F detector spacing (at 2mm) ~1mm 2 bolometers 8x32 Mechanical Model Light

Filled Detector Arrays 8x32 Prototype ACT array (Judy Lau) ACT first light instrument

Telescope

ACT - Atacama Cosmology Telescope Remote Controlled Flexible Focal Plane Near the ALMA Site Highly rigid structure 6 Meter Aperture (F~1) Low Ground Pickup (< 20µK dc) No Moving Optics Scan in azimuth by 5 o in 5-6 s No existing telescope incorporates the features required for these measurements. Extreme control of potential systematic errors.

ACT at AMEC Dynamic Structures in PoCo, B.C. (Sept 06)

port of Vancouver Shipped early Jan 2007

ACT in Chile March 2007 Photos: M. Limon

ACT in Chile March 2007 Photos: M. Limon

ACT in Chile March 2007 Photos: M. Limon

ACT in Chile March 2007 Photos: M. Limon

ACT in Chile March 2007 Photos: M. Limon

ACT in Chile March 2007 Photos: M. Limon

Site

Location, Location, Location! 5200 meter elevation One of driest places on planet Gently sloping topography  low turbulence The future site for ALMA Logistical support available Only 26 hours travel from East Coast to site The Atacama in Chile: The ideal site for our science.

Sky Coverage ACT’s sky coverage overlaps with that of Northern and Southern hemisphere telescopes.

From Carlos Hernandez-Monteaugo The Act Strip 2 o wide strip in declination centered at o Galactic coords

ACT – 5200 meters APEX ALMA Support Devlin

TOCO Site ALMA ACT – 5200 meters Cerro Toco

Cross Linked Scan Strategy is Crucial to Making Maps on Degree Angular Scales 240 square degrees in circle 100 square degrees for CMB Connect to MAP satellite for calibration No cross-linking Single cross-linked scan Simulations by Tobias Marriage

Supporting Observations

Blanco Cosmology Survey Mosaic Camera on 4-m Blanco Telescope (J Mohr, PI) Observations –2/3 (30/45 nights) now complete –4 bands: griz –Current sky area coverage 100 ptgs (5 hr field) 19 ptgs (23 hr field) ACT Strip  = 2 o ACT Strip  = 2 o

Blanco Cosmology Survey ACT-team Data Reduction –Developed full reduction pipeline using mscred tools in IRAF Applies all basic analysis steps resulting in merged final images registered to the sky –Photometry pipeline developed and zeropoints generated on nightly basis –Object catalogs being generated 1/100 of 50 sq-degrees 1/6400 of 50 sq-degrees Cluster detection underway Galaxy-galaxy lensing under investigation F. Menanteau

Galex Survey GALEX Survey of the Atacama Cosmology Telescope Strip (R Jimenez, PI) –Cycle 3 approved –207 ks Legacy program –Obtain UV photometry to improve photo-z accuracy –Study star formation history at z<0.5

X-ray Survey Approximately 0.5 Ms awarded by XMM-Newton (Hans Bohringer, PI) “A Coordinated XMM, SZE, and Optical Survey for Galaxy Cluster Cosmology” AO-6 Observation period (May 07-May 08) Current baseline plan: 44 separate 12-ks pointings covering 6.5 sq-deg total Located within optical survey (low extinction 23h BCS field) where ACT and SPT are to observe as well X-ray flux sensitivity of 6.5x erg/s/cm 2 (0.5-2 keV) (100 fainter than ROSAT All Sky Survey) Expect to detect clusters

X-ray Clusters 1ES z=0.296 Abell 3404 z=0.167 XMM RXC J Abell S0520 z= XMM

ACT Status/Schedule Current approximate schedule Deploying telescope in Atacama now Finish install/align/debug telescope (~2 months) Use single band 8x32 detector for first light Single band MBAC observations (32x 32 detector) during austral winter this year Full up 3 color MBAC observations in 2008

Properties of Known Clusters CTIO 1.5 m

SALT Status Telescope Inaugurated: Nov. 05 Performance Verification Observations: 06 50% Science Time, 50% Engineering: Sept 06 All instrument modes verified Direct ImageryHigh Speed Photometry Polarimetry Long-Slit SpectroscopyMulti-Slit Spectroscopy Fabry-Perot SpectroscopySpectro-Polarimetry First Scientific Publication: First science with the Southern African Large Telescope: peering at the accreting polar caps of the eclipsing polar SDSS J O'Donoghue, D. et al. MNRAS 372, , 2006

Sample SALT Science Direct & RSS Fabry-Perot: NGC 1365 Multi-Slit Spectroscopy: NGC 6822

32 x 32 array 0.4° x 0.4° Ground-based Mapping – Dealing with Elevation Induced Gradients A 7K zenith temperature gives a 165 mK/deg gradient at an observing angle of 45°. From the upper row to the bottom row of the array there is a 65 mK gradient. => Over 1000 times the signal level! 65 mK This gradient exists for any of the best observing sites. How can you make a true 2D map in the presence of such a large gradient?

SCP Horizon West Scan 208 Az, 45 el East Scan 152 Az, 45 el East or West scan at Constant Elevation. 2° peak to peak Cross-linked Scans Modulation on multiple time scales: 20 ms – pixel transit along scan 1 second – array transit 3 seconds – chop 9 seconds – pixel drift 3 minutes – array drift 7 hours – E-W scans 1 day – repeat same scans => Very low atmospheric offset.

Cross-linked and Overlapping Scans Subtract a single level and gradient from East and West scans to link at the center. The largest total offset before full interlocking mapping solution, at l ~ 300, is less than 100 µK. Each detector samples all points of the map without EVER changing elevation. Multiple pixels per PSF. Produce many 1.4° x 1.4° maps. East Scan West Scan All scans done at constant elevation. Cross-linking key to MAP, PLANCK, BOOMERanG, MAXIMA, QMAP

ACT Schedule Assemble telescope at factory: 4/15/06 Install MBAC and test telescope: 5/1/06 – 6/16/06 7/1/06 Factory Acceptance: 6/20/06 7/2/06 Disassemble (3-4 parts) and ship to Chile: 7/20/06 8/20/06 Assemble in San Pedro: 8/06 – 9/06 9/06-10/06 Install at site – 9/06 – 10/06 10/06-11/06 Site Acceptance Test: 10/06 11/06 Install receiver and first light: 11/06 12/06

SZ Studies Cluster physics, evolution of structure Follow-up redshifts + mass estimates (optical – SALT)(x-ray, lensing, or velocity dispersions)  N cluster (m,z) Sensitive to both w and neutrino mass w  0, earlier dark energy domination  fewer low-z clusters relative to high-z m    suppression of growth of structure

How a TES Bolometer Works TES Detector features good noise performance, high sensitivity, high speed, linear behavior Increasing P opt raises TES T and increases resistance. Device is voltage biased, so Joule heating decreases. We measure reduction in current with SQUID. Acceptable time constant of device 40  s <  det < 400  s. Multiplexed readouts have been developed, permitting large arrays with simple electronics T bias T bath G C Absorber R TES P ohm =V 2 bias /R TES P cool =P opt +P ohm P opt