Design and initial performance of SHARP, a polarimeter for the SHARC-II camera at the Caltech Submillimeter Observatory

Li, H.; Dowell, C. D.; Kirby, Larry; Novak, Giles; Vaillancourt, John E.

doi:10.1364/ao.47.000422

Cited by 42 publications

(45 citation statements)

References 28 publications

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“…Polarisation analysis of the 620.701 GHz maser components Linear polarisation measurements are often optimised to determine the Stokes Q and U parameters independently from each other (Li et al 2008;Hezareh & Houde 2010). If we define four intensity measurements I ϕ within the equatorial system with ϕ set to 0 • when pointing north and increasing eastwards, then…”

Section: Hifi Observations At 620701 Ghzmentioning

confidence: 99%

Polarisation observations of VY Canis Majoris H₂O 5₃₂–4₄₁620.701 GHz maser emission with HIFI

Harwit¹,

Houde²,

Sonnentrucker

et al. 2010

A&A

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Context. Water vapour maser emission from evolved oxygen-rich stars remains poorly understood. Additional observations, including polarisation studies and simultaneous observation of different maser transitions may ultimately lead to greater insight. Aims. We have aimed to elucidate the nature and structure of the VY CMa water vapour masers in part by observationally testing a theoretical prediction of the relative strengths of the 620.701 GHz and the 22.235 GHz maser components of ortho H 2 O. Methods. In its high-resolution mode (HRS) the Herschel Heterodyne Instrument for the Far Infrared (HIFI) offers a frequency resolution of 0.125 MHz, corresponding to a line-of-sight velocity of 0.06 km s −1 , which we employed to obtain the strength and linear polarisation of maser spikes in the spectrum of VY CMa at 620.701 GHz. Simultaneous ground based observations of the 22.235 GHz maser with the Max-PlanckInstitut für Radioastronomie 100-m telescope at Effelsberg, provided a ratio of 620.701 GHz to 22.235 GHz emission. Results. We report the first astronomical detection to date of H 2 O maser emission at 620.701 GHz. In VY CMa both the 620.701 and the 22.235 GHz polarisation are weak. At 620.701 GHz the maser peaks are superposed on what appears to be a broad emission component, jointly ejected from the star. We observed the 620.701 GHz emission at two epochs 21 days apart, both to measure the potential direction of linearly polarised maser components and to obtain a measure of the longevity of these components. Although we do not detect significant polarisation levels in the core of the line, they rise up to approximately 6% in its wings.

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Section: Hifi Observations At 620701 Ghzmentioning

confidence: 99%

Polarisation observations of VY Canis Majoris H₂O 5₃₂–4₄₁620.701 GHz maser emission with HIFI

Harwit¹,

Houde²,

Sonnentrucker

et al. 2010

A&A

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“…The understanding of the physical phenomena responsible for polarized interstellar emission provides valuable information about the underlying astrophysical processes, an important example being the formation and evolution of stars. Since the 1990s, polarimetry techniques and instruments have been developed for a wide range of wavelengths, from optical (e.g., Magalhaes et al 1996;Wiktorowicz & Matthews 2008) to the submillimeter and radio regimes (e.g., Platt et al 1991;Hildebrand et al 1997;Shinnaga & Tsuboi 1999;Greaves et al 2003;Li et al 2008;Thum et al 2008;Hildebrand et al 2009;Houde et al 2009;Heiles 2001;Heiles et al 2001aHeiles et al , 2001b.…”

Section: Introductionmentioning

confidence: 99%

A Four-Stokes-Parameter Spectral Line Polarimeter at the Caltech Submillimeter Observatory

Hezareh¹,

Houde²

2010

PUBL ASTRON SOC PAC

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ABSTRACT. We designed and built a new Four-Stokes-Parameter spectral line Polarimeter (FSPPol) for the Caltech Submillimeter Observatory (CSO). The simple design of FSPPol does not include any mirrors or optical components to redirect or reimage the radiation beam and simply transmits the beam to the receiver through its retarder plates. FSPPol is currently optimized for observation in the 200-260 GHz range and measures all four Stokes parameters, I, Q, U, and V . The very low level of instrument polarization makes it possible to obtain reliable measurements of the Goldreich-Kylafis effect in molecular spectral lines. Accordingly, we measured a polarization fraction of a few percent in the spectral line wings of 12 CO (J ¼ 2 → 1) in Orion KL/IRc2, which is consistent with previous observations. We also used FSPPol to study the Zeeman effect in the N ¼ 2 → 1 transition of CN in DR21(OH) for the first time. At this point we cannot report a Zeeman detection, but more observations are ongoing.

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“…Refers to shortest wavelength for polarimeters with several bands. References: (1) Platt et al (1991), (2) Schleuning et al (1997), (3) Dowell et al (1998), (4) Holland et al (1999), (5) Greaves et al (2003), (6) Dowell et al (2003), (7) Li et al (2008), (8) Krejny et al (2008), (9) (Aumont et al 2010, 27 fwhm) and JCMT/SCUPOL (Matthews et al 2009, 20 fwhm) are shown for comparison.…”

Section: Discussionmentioning

confidence: 99%

Submillimeter polarimetry with PolKa, a reflection-type modulator for the APEX telescope

Wiesemeyer

Hezareh

Kreysa

et al. 2014

2014 39th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz)

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Imaging polarimetry is an important tool for the study of cosmic magnetic fields. In our Galaxy, polarization levels of a few up to ∼10% are measured in the submillimeter dust emission from molecular clouds and in the synchrotron emission from supernova remnants. Only few techniques exist to image the distribution of polarization angles, as a means of tracing the plane-of-sky projection of the magnetic field orientation. At submillimeter wavelengths, polarization is either measured as the differential total power of polarization-sensitive bolometer elements, or by modulating the polarization of the signal. Bolometer arrays such as LABOCA at the APEX telescope are used to observe the continuum emission from fields as large as ∼ 0.• 2 in diameter. Here we present PolKa, a polarimeter for LABOCA with a reflection-type waveplate of at least 90% efficiency.The modulation efficiency depends mainly on the sampling and on the angular velocity of the waveplate. For the data analysis the concept of generalized synchronous demodulation is introduced. The instrumental polarization towards a point source is at the level of ∼ 0.1%, increasing to a few percent at the −10db contour of the main beam. A method to correct for its effect in observations of extended sources is presented. Our map of the polarized synchrotron emission from the Crab nebula is in agreement with structures observed at radio and optical wavelengths. The linear polarization measured in OMC1 agrees with results from previous studies, while the high sensitivity of LABOCA enables us to also map the polarized emission of the Orion Bar, a prototypical photon-dominated region.

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Design and initial performance of SHARP, a polarimeter for the SHARC-II camera at the Caltech Submillimeter Observatory

Cited by 42 publications

References 28 publications

Polarisation observations of VY Canis Majoris H₂O 5₃₂–4₄₁620.701 GHz maser emission with HIFI

Polarisation observations of VY Canis Majoris H₂O 5₃₂–4₄₁620.701 GHz maser emission with HIFI

A Four-Stokes-Parameter Spectral Line Polarimeter at the Caltech Submillimeter Observatory

Submillimeter polarimetry with PolKa, a reflection-type modulator for the APEX telescope

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Design and initial performance of SHARP, a polarimeter for the SHARC-II camera at the Caltech Submillimeter Observatory

Cited by 42 publications

References 28 publications

Polarisation observations of VY Canis Majoris H2O 532–441620.701 GHz maser emission with HIFI

Polarisation observations of VY Canis Majoris H2O 532–441620.701 GHz maser emission with HIFI

A Four-Stokes-Parameter Spectral Line Polarimeter at the Caltech Submillimeter Observatory

Submillimeter polarimetry with PolKa, a reflection-type modulator for the APEX telescope

Contact Info

Product

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Polarisation observations of VY Canis Majoris H₂O 5₃₂–4₄₁620.701 GHz maser emission with HIFI

Polarisation observations of VY Canis Majoris H₂O 5₃₂–4₄₁620.701 GHz maser emission with HIFI