Laura Fissel

Publications (5)6.02 Total impact

• Article: Empirical modelling of the BLASTPol achromatic half-wave plate for precision submillimetre polarimetry

  Lorenzo Moncelsi, Peter Ade, Francesco Elio Angile, Steven Benton, Mark Devlin, Laura Fissel, Natalie Gandilo, Joshua Gundersen, Tristan Matthews, C. Barth Netterfield, [......], David Nutter, Enzo Pascale, Frederick Poidevin, Giorgio Savini, Douglas Scott, Juan Soler, Locke Spencer, Matthew Truch, Gregory Tucker, Jin Zhang
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  ABSTRACT: A cryogenic achromatic half-wave plate (HWP) for submillimetre astronomical polarimetry has been designed, manufactured, tested, and deployed in the Balloon-borne Large-Aperture Submillimeter Telescope for Polarimetry (BLASTPol). The design is based on the five-slab Pancharatnam recipe and it works in the wavelength range 200-600 micron, making it the most achromatic HWP built to date at submillimetre wavelengths. The frequency behaviour of the HWP has been fully characterised at room and cryogenic temperatures with incoherent radiation from a polarising Fourier transform spectrometer. We develop a novel empirical model, complementary to the physical and analytical ones available in the literature, that allows us to recover the HWP Mueller matrix and phase shift as a function of frequency and extrapolated to 4K. We show that most of the HWP non-idealities can be modelled by quantifying one wavelength-dependent parameter, the position of the HWP equivalent axes, which is then readily implemented in a map-making algorithm. We derive this parameter for a range of spectral signatures of input astronomical sources relevant to BLASTPol, and provide a benchmark example of how our method can yield unprecedented accuracy on measurements of the polarisation angle on the sky at submillimetre wavelengths.
  08/2012;
• Source

  Available from: ArXiv

  Article: Substellar Objects in Nearby Young Clusters (SONYC) III: Chamaeleon-I

  Koraljka Muzic, Alexander Scholz, Vincent Geers, Laura Fissel, Ray Jayawardhana
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  ABSTRACT: SONYC - Substellar Objects in Nearby Young Clusters - is a survey program to investigate the frequency and properties of substellar objects with masses down to a few times that of Jupiter in nearby star-forming regions. In this third paper, we present our recent results in the Chamaeleon-I star forming region. We have carried out deep optical and near-infrared imaging in four bands (I, z, J, Ks) using VIMOS on the ESO Very Large Telescope and SOFI on the New Technology Telescope, and combined our data with mid-infrared data from the Spitzer Space Telescope. The survey covers ~0.25 sqdeg on the sky, and reaches completeness limits of 23.0 in the I-band, 18.3 in the J-band, and 16.7 in Ks-band. Follow-up spectroscopy of the candidates selected from the optical photometry (I <~ 21) was carried out using the multi-object spectrograph VIMOS on the VLT. We identify 13 objects consistent with M spectral types, 11 of which are previously known M-dwarfs with confirmed membership in the cluster. The 2 newly reported objects have effective temperatures above the substellar limit. We also present two new candidate members of Chamaeleon-I, selected from our JK photometry combined with the Spitzer data. Based on the results of our survey, we estimate that the number of missing very-low-mass members down to ~0.008 MSun and Av <= 5 is <= 7, i.e. <= 3% of the total cluster population according to the current census.
  03/2011;
• Source

  Available from: Rebecca Tucker

  Article: Modeling and characterization of the SPIDER half-wave plate.

  Sean A Bryan, Peter A R Ade, Mandana Amiri, Steve Benton, Richard Bihary, James J Bock, J Richard Bond, Joseph A Bonetti, H Cynthia Chiang, Carlo R Contaldi, [......], Daniel Riley, John E Ruhl, Marcus C Runyan, Matthew A Schenker, Jamil Shariff, Juan Diego Soler, Amy Trangsrud, Rebecca Tucker, Carole Tucker, Anthony Turner
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  ABSTRACT: Spider is a balloon-borne array of six telescopes that will observe the Cosmic Microwave Background. The 2624 antenna-coupled bolometers in the instrument will make a polarization map of the CMB with approximately one-half degree resolution at 145 GHz. Polarization modulation is achieved via a cryogenic sapphire half-wave plate (HWP) skyward of the primary optic. We have measured millimeter-wave transmission spectra of the sapphire at room and cryogenic temperatures. The spectra are consistent with our physical optics model, and the data gives excellent measurements of the indices of A-cut sapphire. We have also taken preliminary spectra of the integrated HWP, optical system, and detectors in the prototype Spider receiver. We calculate the variation in response of the HWP between observing the CMB and foreground spectra, and estimate that it should not limit the Spider constraints on inflation.
  06/2010;
• Source

  Available from: ArXiv

  Article: Substellar Objects in Nearby Young Clusters (SONYC): The Bottom of the Initial Mass Function in NGC 1333

  Alexander Scholz, Vincent Geers, Ray Jayawardhana, Laura Fissel, Eve Lee, David Lafreniere, and Motohide Tamura
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  ABSTRACT: SONYC—Substellar Objects in Nearby Young Clusters—is a survey program to investigate the frequency and properties of substellar objects with masses down to a few times that of Jupiter in nearby star-forming regions. Here, we present the first results from SONYC observations of NGC 1333, a ~1 Myr old cluster in the Perseus star-forming complex. We have carried out extremely deep optical and near-infrared imaging in four bands (i', z', J, K) using Subaru Prime Focus Camera and Multi-Object InfraRed Camera and Spectrograph (MOIRCS) instruments at the Subaru telescope. The survey covers 0.25 deg2 and reaches completeness limits of 24.7 mag in the i' band and 20.8 mag in the J band. We select 196 candidates with colors as expected for young, very low mass objects. Follow-up multi-object spectroscopy with MOIRCS is presented for 53 objects. We confirm 19 objects as likely brown dwarfs (BDs) in NGC 1333, seven of them previously known. Nine additional objects are classified as possible stellar cluster members, likely with early to mid M spectral types. The confirmed objects are strongly clustered around the peak in the gas distribution and the core of the cluster of known stellar members. For 11 of them, we confirm the presence of disks based on Spitzer/Infrared Array Camera photometry. The effective temperatures for the BD sample range from 2500 K to 3000 K, which translates to masses of ~0.015-0.1 M ☉, based on model evolutionary tracks. For comparison, the completeness limit of our survey translates to mass limits of 0.004 M ☉ for AV 5 mag or 0.008 M ☉ for AV 10 mag. Compared with other star-forming regions, NGC 1333 shows an overabundance of BDs relative to low-mass stars, by a factor of 2-5. On the other hand, NGC 1333 has a deficit of planetary-mass objects: based on the surveys in σ Orionis, the Orion Nebula Cluster and Chamaeleon I, the expected number of planetary-mass objects in NGC 1333 is 8-10, but we find none. It is plausible that our survey has detected the minimum mass limit for star formation in this particular cluster, at around 0.012-0.02 M ☉. If confirmed, our findings point to significant regional/environmental differences in the number of BDs and the minimum mass of the initial mass function.
  The Astrophysical Journal 08/2009; 702(1):805. · 6.02 Impact Factor
• Article: An Unbiased Survey of 500 Nearby Stars for Debris Disks: A JCMT Legacy Program

  Brenda Matthews, Jane S. Greaves, Wayne S. Holland, Mark C. Wyatt, Michael J. Barlow, Pierre Bastien, Chas. A. Beichman, Andrew Biggs, Harold M. Butner, William R. Dent, James Di Francesco, Carsten Dominik, Laura Fissel, Per Friberg, A. G. Gibb, Mark Halpern, R. J. Ivison, Ray Jayawardhana, Tim Jenness