Matthew Hasselfield

Detection of

We report results from the BICEP2 experiment, a cosmic microwave background (CMB) polarimeter specifically designed to search for the signal of inflationary gravitational waves in the B-mode power spectrum around ℓ∼80. The telescope comprised a 26 cm aperture all-cold refracting optical system equipped with a focal plane of 512 antenna coupled transition edge sensor 150 GHz bolometers each with temperature sensitivity of ≈300  μK(CMB)√s. BICEP2 observed from the South Pole for three seasons from 2010 to 2012. A low-foreground region of sky with an effective area of 380 square deg was observed to a depth of 87 nK deg in Stokes Q and U. In this paper we describe the observations, data reduction, maps, simulations, and results. We find an excess of B-mode power over the base lensed-ΛCDM expectation in the range 30 < ℓ < 150, inconsistent with the null hypothesis at a significance of >5σ. Through jackknife tests and simulations based on detailed calibration measurements we show that systematic contamination is much smaller than the observed excess. Cross correlating against WMAP 23 GHz maps we find that Galactic synchrotron makes a negligible contribution to the observed signal. We also examine a number of available models of polarized dust emission and find that at their default parameter values they predict power ∼(5-10)× smaller than the observed excess signal (with no significant cross-correlation with our maps). However, these models are not sufficiently constrained by external public data to exclude the possibility of dust emission bright enough to explain the entire excess signal. Cross correlating BICEP2 against 100 GHz maps from the BICEP1 experiment, the excess signal is confirmed with 3σ significance and its spectral index is found to be consistent with that of the CMB, disfavoring dust at 1.7σ. The observed B-mode power spectrum is well fit by a lensed-ΛCDM+tensor theoretical model with tensor-to-scalar ratio r = 0.20_(-0.05)(+0.07), with r = 0 disfavored at 7.0σ. Accounting for the contribution of foreground, dust will shift this value downward by an amount which will be better constrained with upcoming data sets.

B

We report the first detection of the gravitational lensing of the cosmic microwave background through a measurement of the four-point correlation function in the temperature maps made by the Atacama Cosmology Telescope. We verify our detection by calculating the levels of potential contaminants and performing a number of null tests. The resulting convergence power spectrum at 2° angular scales measures the amplitude of matter density fluctuations on comoving length scales of around 100 Mpc at redshifts around 0.5 to 3. The measured amplitude of the signal agrees with Lambda cold dark matter cosmology predictions. Since the amplitude of the convergence power spectrum scales as the square of the amplitude of the density fluctuations, the 4σ detection of the lensing signal measures the amplitude of density fluctuations to 12%.

-Mode Polarization at Degree Angular Scales by BICEP2

We present measurements of the cosmic microwave background (CMB) power spectrum made by the Atacama Cosmology Telescope at 148 GHz and 218 GHz, as well as the cross-frequency spectrum between the two channels. Our results clearly show the second through the seventh acoustic peaks in the CMB power spectrum. The measurements of these higher-order peaks provide an additional test of the ΛCDM cosmological model. At l>3000, we detect power in excess of the primary anisotropy spectrum of the CMB. At lower multipoles 500 < l < 3000, we find evidence for gravitational lensing of the CMB in the power spectrum at the 2.8σ level. We also detect a low level of Galactic dust in our maps, which demonstrates that we can recover known faint, diffuse signals.

Detection of the power spectrum of cosmic microwave background lensing by the Atacama Cosmology Telescope.

The Atacama Cosmology Telescope was designed to measure small-scale anisotropies in the Cosmic Microwave Background and detect galaxy clusters through the Sunyaev-Zel’dovich effect. The instrument is located on Cerro Toco in the Atacama Desert, at an altitude of 5190 meters. A six-meter off-axis Gregorian telescope feeds a new type of cryogenic receiver, the Millimeter Bolometer Array Camera. The receiver features three 1000-element arrays of transition-edge sensor bolometers for observations at 148GHz, 218GHz, and 277GHz. Each detector array is fed by free space mm-wave optics. Each frequency band has a field of view of approximately 22 × 26. The telescope was commissioned in 2007 and has completed its third year of operations. We discuss the major components of the telescope, camera, and related systems, and summarize the instrument performance. Subject headings: Microwave Telescopes, CMB Observations

The Atacama Cosmology Telescope: a measurement of the cosmic microwave background power spectrum at 148 and 218 GHz from the 2008 southern survey

We present a joint analysis of the overlapping Balloon-borne Large Aperture Submillimetre Telescope (BLAST) 250, 350, 500 μm, and LABOCA 870 μm observations [from the LABOCA ECDFS Submm Survey (LESS) survey] of the Extended Chandra Deep Field-South. Out to z∼ 3, the BLAST filters sample near the peak wavelength of thermal far-infrared (FIR) emission from galaxies (rest-frame wavelengths ∼60–200 μm), primarily produced by dust heated through absorption in star-forming clouds. However, identifying counterparts to individual BLAST peaks is very challenging, given the large beams [full-width at half-maximum (FWHM) 36–60 arcsec]. In contrast, the ground-based 870 μm observations have a significantly smaller 19 arcsec FWHM beam, and are sensitive to higher redshifts (z∼ 1–5, and potentially beyond) due to the more favourable negative K-correction. We use the LESS data, as well as deep Spitzer and VLA imaging, to identify 118 individual sources that produce significant emission in the BLAST bands. We characterize the temperatures and FIR luminosities for a subset of 69 sources which have well-measured submillimetre (submm) spectral energy distributions (SEDs) and redshift measurements out to z∼ 3. For flux-limited sub-samples in each BLAST band, and a dust emissivity index β= 2.0, we find a median temperature T= 30 K (all bands) as well as median redshifts: z= 1.1 (interquartile range 0.2–1.9) for S250 > 40 mJy; z= 1.3 (interquartile range 0.6–2.1) for S350 > 30 mJy; and z= 1.6 (interquartile range 1.3–2.3) for S500 > 20 mJy. Taking into account the selection effects for our survey (a bias towards detecting lower-temperature galaxies), we find no evidence for evolution in the local FIR–temperature correlation out to z∼ 2.5. Comparing with star-forming galaxy SED templates, about 8 per cent of our sample appears to exhibit significant excesses in the radio and/or mid-IR, consistent with those sources harbouring active galactic nuclei (AGN). Since our statistical approach differs from most previous studies of submm galaxies, we describe the following techniques in two appendices: our ‘matched filter’ for identifying sources in the presence of point-source confusion; and our approach for identifying counterparts using likelihood ratios. This study is a direct precursor to future joint FIR/submm surveys, for which we outline a potential identification and SED measurement strategy.

Overview of the Atacama Cosmology Telescope: receiver, instrumentation, and telescope systems

For the first time, measurements of the cosmic microwave background radiation (CMB) alone favor cosmologies with w = -1 dark energy over models without dark energy at a 3.2-sigma level. We demonstrate this by combining the CMB lensing deflection power spectrum from the Atacama Cosmology Telescope with temperature and polarization power spectra from the Wilkinson Microwave Anisotropy Probe. The lensing data break the geometric degeneracy of different cosmological models with similar CMB temperature power spectra. Our CMB-only measurement of the dark energy density Ω(Λ) confirms other measurements from supernovae, galaxy clusters, and baryon acoustic oscillations, and demonstrates the power of CMB lensing as a new cosmological tool.

A joint analysis of BLAST 250–500 μm and LABOCA 870 μm observations in the Extended Chandra Deep Field-South

Erminia Calabrese, Renée A. Hlozek, Nick Battaglia, Elia S. Battistelli, J. Richard Bond, Jens Chluba, Devin Crichton, Sudeep Das, 8 Mark J. Devlin, Joanna Dunkley, Rolando Dünner, Marzieh Farhang, 11 Megan B. Gralla, Amir Hajian, Mark Halpern, Matthew Hasselfield, 12 Adam D. Hincks, Kent D. Irwin, Arthur Kosowsky, Thibaut Louis, Tobias A. Marriage, 2, 15 Kavilan Moodley, Laura Newburgh, Michael D. Niemack, 13, 17 Michael R. Nolta, Lyman A. Page, Neelima Sehgal, Blake D. Sherwin, Jonathan L. Sievers, Cristóbal Sifón, David N. Spergel, Suzanne T. Staggs, Eric R. Switzer, and Edward J. Wollack Sub-department of Astrophysics, University of Oxford, Keble Road, Oxford OX1 3RH, UK Dept. of Astrophysical Sciences, Peyton Hall, Princeton University, Princeton, NJ 08544, USA Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA Department of Physics, University of Rome ‘Sapienza’, Piazzale Aldo Moro 5, I-00185 Rome, Italy CITA, University of Toronto, Toronto, ON M5S 3H8, Canada Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218-2686, USA High Energy Physics Division, Argonne National Laboratory, 9700 S Cass Avenue, Lemont, IL 60439, USA BCCP, LBL and Department of Physics, University of California, Berkeley, CA 94720, USA Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd St., Philadelphia,PA 19104,USA Departamento de Astronomı́a y Astrof́ısica, Pontifićıa Universidad Católica de Chile, Casilla 306, Santiago 22, Chile Department of Astronomy and Astrophysics, University of Toronto, 50 St George , Toronto, ON, M5S 3H4 Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z4, Canada NIST Quantum Devices Group, 325 Broadway Mailcode 817.03, Boulder, CO 80305, USA Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260, USA Joseph Henry Laboratories of Physics, Jadwin Hall, Princeton University, Princeton, NJ 08544,USA Astrophysics and Cosmology Research Unit, School of Mathematical Sciences, University of KwaZulu-Natal, Durban, 4041, South Africa Department of Physics, Cornell University, Ithaca, NY, USA 14853 Physics and Astronomy Department, Stony Brook University, Stony Brook, NY 11794-3800, USA Leiden Observatory, Leiden University, PO Box 9513, NL-2300 RA Leiden, Netherlands NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA

Evidence for dark energy from the cosmic microwave background alone using the Atacama Cosmology Telescope lensing measurements.

We report on extragalactic sources detected in a 455 deg2 map of the southern sky made with data at a frequency of 148 GHz from the Atacama Cosmology Telescope (ACT) 2008 observing season. We provide a catalog of 157 sources with flux densities spanning two orders of magnitude: from 15 mJy to 1500 mJy. Comparison to other catalogs shows that 98% of the ACT detections correspond to sources detected at lower radio frequencies. Three of the sources appear to be associated with the brightest cluster galaxies of low-redshift X-ray-selected galaxy clusters. Estimates of the radio to millimeter-wave spectral indices and differential counts of the sources further bolster the hypothesis that they are nearly all radio sources, and that their emission is not dominated by re-emission from warm dust. In a bright (>50 mJy) 148 GHz selected sample with complete cross-identifications from the Australia Telescope 20 GHz survey, we observe an average steepening of the spectra between 5, 20, and 148 GHz with median spectral indices of α5-20 = –0.07 ± 0.06, α20-148 = –0.39 ± 0.04, and α5-148 = –0.20 ± 0.03. When the measured spectral indices are taken into account, the 148 GHz differential source counts are consistent with previous measurements at 30 GHz in the context of a source count model dominated by radio sources. Extrapolating with an appropriately rescaled model for the radio source counts, the Poisson contribution to the spatial power spectrum from synchrotron-dominated sources with flux density less than 20 mJy is C Sync = (2.8 ± 0.3) × 10–6μK2.

Cosmological parameters from pre-planck cosmic microwave background measurements

We describe SPIDER, a balloon-borne instrument to map the polarization of the millimeter-wave sky with degree angular resolution. Spider consists of six monochromatic refracting telescopes, each illuminating a focal plane of large-format antenna-coupled bolometer arrays. A total of 2,624 superconducting transition-edge sensors are distributed among three observing bands centered at 90, 150, and 280 GHz. A cold half-wave plate at the aperture of each telescope modulates the polarization of incoming light to control systematics. SPIDERs first flight will be a 20-30-day Antarctic balloon campaign in December 2011. This flight will map ~8% of the sky to achieve unprecedented sensitivity to the polarization signature of the gravitational wave background predicted by inflationary cosmology. The SPIDER mission will also serve as a proving ground for these detector technologies in preparation for a future satellite mission.

The Atacama Cosmology Telescope: Extragalactic Sources at 148 GHz in the 2008 Survey

We present a measurement of the gravitational lensing of the Cosmic Microwave Background (CMB) temperature and polarization fields obtained by cross-correlating the reconstructed convergence signal from the first season of Atacama Cosmology Telescope Polarimeter data at 146 GHz with Cosmic Infrared Background (CIB) fluctuations measured using the Planck satellite. Using an effective overlap area of 92.7 square degrees, we detect gravitational lensing of the CMB polarization by large-scale structure at a statistical significance of