arXiv subjects

C. J. MacTavish

Publications and source records attributed to C. J. MacTavish.

27 records · Page 2Linked to original sources

arXiv2009

BOOMERanG Constraints on Primordial Non-Gaussianity from Analytical Minkowski Functionals

We use Minkowski Functionals (MF) to constrain a primordial non-Gaussian contribution to the CMB intensity field as observed in the 150 GHz and 145 GHz BOOMERanG maps from the 1998 and 2003 flights, respectively, performing for the first time a joint analysis of the two datasets. A perturbative expansion of the MF formulae in the limit of a weakly non-Gaussian field yields analytical formulae, derived by Hikage et al. (2006), which can be used to constrain the coupling parameter f_NL without the need for non-Gaussian simulations. We find -1020<f_NL<390 at 95% CL, significantly improving the previous constraints by De Troia et al. (2007) on the BOOMERanG 2003 dataset. These are the best f_NL limits to date for suborbital probes.

astro-ph.CO↗

arXiv2008

The Balloon-borne Large-Aperture Submillimeter Telescope for Polarization: BLAST-pol

The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) is a sub-orbital experiment designed to study the process of star formation in local galaxies (including the Milky Way) and in galaxies at cosmological distances. Using a 2-m Cassegrain telescope, BLAST images the sky onto a focal plane, which consists of 270 bolometric detectors split between three arrays, observing simultaneously in 30% wide bands, centered at 250, 350, and 500 microns. The diffraction-limited optical system provides a resolution of 30" at 250 microns. The pointing system enables raster-like scans with a positional accuracy of ~30", reconstructed to better than 5" rms in post-flight analysis. BLAST had two successful flights, from the Arctic in 2005, and from Antarctica in 2006, which provided the first high-resolution and large-area (~0.8-200 deg^2) submillimeter surveys at these wavelengths. As a pathfinder for the SPIRE instrument on Herschel, BLAST shares with the ESA satellite similar focal plane technology and scientific motivation. A third flight in 2009 will see the instrument modified to be polarization-sensitive (BLAST-Pol). With its unprecedented mapping speed and resolution, BLAST-Pol will provide insights into Galactic star-forming nurseries, and give the necessary link between the larger, coarse resolution surveys and the narrow, resolved observations of star-forming structures from space and ground based instruments being commissioned in the next 5 years.

astro-ph↗

arXiv2008

SPIDER: A Balloon-borne Large-scale CMB Polarimeter

Spider is a balloon-borne experiment that will measure the polarization of the Cosmic Microwave Background over a large fraction of a sky at 1 degree resolution. Six monochromatic refracting millimeter-wave telescopes with large arrays of antenna-coupled transition-edge superconducting bolometers will provide system sensitivities of 4.2 and 3.1 micro K_cmb rt s at 100 and 150 GHz, respectively. A rotating half-wave plate will modulate the polarization sensitivity of each telescope, controlling systematics. Bolometer arrays operating at 225 GHz and 275 GHz will allow removal of polarized galactic foregrounds. In a 2-6 day first flight from Alice Springs, Australia in 2010, Spider will map 50% of the sky to a depth necessary to improve our knowledge of the reionization optical depth by a large factor.

astro-ph↗

arXiv2008

The Balloon-borne Large Aperture Submillimeter Telescope: BLAST

The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) is a sub-orbital surveying experiment designed to study the evolutionary history and processes of star formation in local galaxies (including the Milky Way) and galaxies at cosmological distances. The BLAST continuum camera, which consists of 270 detectors distributed between 3 arrays, observes simultaneously in broad-band (30%) spectral-windows at 250, 350, and 500 microns. The optical design is based on a 2m diameter telescope, providing a diffraction-limited resolution of 30" at 250 microns. The gondola pointing system enables raster mapping of arbitrary geometry, with a repeatable positional accuracy of ~30"; post-flight pointing reconstruction to ~5" rms is achieved. The on-board telescope control software permits autonomous execution of a pre-selected set of maps, with the option of manual override. In this paper we describe the primary characteristics and measured in-flight performance of BLAST. BLAST performed a test-flight in 2003 and has since made two scientifically productive long-duration balloon flights: a 100-hour flight from ESRANGE (Kiruna), Sweden to Victoria Island, northern Canada in June 2005; and a 250-hour, circumpolar-flight from McMurdo Station, Antarctica, in December 2006.

astro-ph↗

arXiv2007

Searching for non Gaussian signals in the BOOMERanG 2003 CMB maps

We analyze the BOOMERanG 2003 (B03) 145 GHz temperature map to constrain the amplitude of a non Gaussian, primordial contribution to CMB fluctuations. We perform a pixel space analysis restricted to a portion of the map chosen in view of high sensitivity, very low foreground contamination and tight control of systematic effects. We set up an estimator based on the three Minkowski functionals which relies on high quality simulated data, including non Gaussian CMB maps. We find good agreement with the Gaussian hypothesis and derive the first limits based on BOOMERanG data for the non linear coupling parameter f_NL as -300<f_NL<650 at 68% CL and -800<f_NL<1050 at 95% CL.

astro-ph↗

arXiv2007

Spider Optimization: Probing the Systematics of a Large Scale B-Mode Experiment

Spider is a long-duration, balloon-borne polarimeter designed to measure large scale Cosmic Microwave Background (CMB) polarization with very high sensitivity and control of systematics. The instrument will map over half the sky with degree angular resolution in I, Q and U Stokes parameters, in four frequency bands from 96 to 275 GHz. Spider's ultimate goal is to detect the primordial gravity wave signal imprinted on the CMB B-mode polarization. One of the challenges in achieving this goal is the minimization of the contamination of B-modes by systematic effects. This paper explores a number of instrument systematics and observing strategies in order to optimize B-mode sensitivity. This is done by injecting realistic-amplitude, time-varying systematics in a set of simulated time-streams. Tests of the impact of detector noise characteristics, pointing jitter, payload pendulations, polarization angle offsets, beam systematics and receiver gain drifts are shown. Spider's default observing strategy is to spin continuously in azimuth, with polarization modulation achieved by either a rapidly spinning half-wave plate or a rapidly spinning gondola and a slowly stepped half-wave plate. Although the latter is more susceptible to systematics, results shown here indicate that either mode of operation can be used by Spider.

astro-ph↗

arXiv2006

Instrumental and Analytic Methods for Bolometric Polarimetry

We discuss instrumental and analytic methods that have been developed for the first generation of bolometric cosmic microwave background (CMB) polarimeters. The design, characterization, and analysis of data obtained using Polarization Sensitive Bolometers (PSBs) are described in detail. This is followed by a brief study of the effect of various polarization modulation techniques on the recovery of sky polarization from scanning polarimeter data. Having been successfully implemented on the sub-orbital Boomerang experiment, PSBs are currently operational in two terrestrial CMB polarization experiments (QUaD and the Robinson Telescope). We investigate two approaches to the analysis of data from these experiments, using realistic simulations of time ordered data to illustrate the impact of instrumental effects on the fidelity of the recovered polarization signal. We find that the analysis of difference time streams takes full advantage of the high degree of common mode rejection afforded by the PSB design. In addition to the observational efforts currently underway, this discussion is directly applicable to the PSBs that constitute the polarized capability of the Planck HFI instrument.

astro-ph↗

arXiv2005

Cosmological Parameters from the 2003 flight of BOOMERANG

We present the cosmological parameters from the CMB intensity and polarization power spectra of the 2003 Antarctic flight of the BOOMERANG telescope. The BOOMERANG data alone constrains the parameters of the $Λ$CDM model remarkably well and is consistent with constraints from a multi-experiment combined CMB data set. We add LSS data from the 2dF and SDSS redshift surveys to the combined CMB data set and test several extensions to the standard model including: running of the spectral index, curvature, tensor modes, the effect of massive neutrinos, and an effective equation of state for dark energy. We also include an analysis of constraints to a model which allows a CDM isocurvature admixture.

astro-ph↗

arXiv2005

A Measurement of the CMB Spectrum from the 2003 Flight of BOOMERANG

We report measurements of the CMB polarization power spectra from the January 2003 Antarctic flight of BOOMERANG. The primary results come from six days of observation of a patch covering 0.22% of the sky centered near R.A. = 82.5 deg., Dec= -45 deg. The observations were made using four pairs of polarization sensitive bolometers operating in bands centered at 145 GHz. Using two independent analysis pipelines, we measure a non-zero signal in the range 100< l <1000 with a significance 4.8-sigma, a 2-sigma upper limit of 8.6 uK^2 for any contribution, and a 2-sigma upper limit of 7.0 uK^2 for the spectrum. Estimates of foreground intensity fluctuations and the non-detection of and signals rule out any significant contribution from galactic foregrounds. The results are consistent with a Lambda-CDM cosmology seeded by adiabatic perturbations. We note that this is the first detection of CMB polarization with bolometric detectors.

astro-ph↗