Cross‐Correlation Spectropolarimetry in Single‐Dish Radio Astronomy

Heiles, Carl

doi:10.1086/323291

Cited by 22 publications

(15 citation statements)

References 7 publications

(7 reference statements)

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“…The full-Stokes data were calibrated using a variation on the procedures described in Heiles (2001); Heiles et al (2001b,a), which we briefly review. A single noise diode is used to inject noise into each of LCP and RCP, and this (coherent) signal is used to determine the phase difference between the two IF paths.…”

Section: Observations and Calibrationmentioning

confidence: 99%

A Limit on the Polarized Anomalous Microwave Emission of Lynds 1622

Mason

Robishaw

Heiles

et al. 2009

ApJ

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The dark cloud Lynds 1622 is one of a few specific sites in the Galaxy where, relative to observed free-free and vibrational dust emission, there is a clear excess of microwave emission. In order to constrain models for this microwave emission, and to better establish the contribution which it might make to ongoing and nearfuture microwave background polarization experiments, we have used the Green Bank Telescope to search for linear polarization at 9.65 Ghz towards Lynds 1622.We place a 95.4% upper limit of 88 µK (123 µK at 99.7% confidence) on the total linear polarization of this source averaged over a 1 ′ .3 FWHM beam. Relative to the observed level of anomalous emission in Stokes I these limits correspond to fractional linear polarizations of 2.7% and 3.5%.

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Section: Observations and Calibrationmentioning

confidence: 99%

A Limit on the Polarized Anomalous Microwave Emission of Lynds 1622

Mason

Robishaw

Heiles

et al. 2009

ApJ

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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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“…Generally, the slopes near 400 MHz averaged to around 0.04 radians/MHz (d V − d H ∼2 m). It is interesting to note that the same quantity was measured at Arecibo (a system significantly different from the one at Green Bank) as approximately 0.1 radians/MHz, or d V − d H ∼5 m [Heiles, 2001].…”

Section: Gain and Phase Difference (Dg Y)mentioning

confidence: 70%

Characterization of system calibration parameters for high gain dual polarization satellite beacon diagnostics of ionospheric variations

et al. 2011

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[1] We present complementary methods for calibrating the dual-polarization feed of a ground-based tracking antenna used for ionospheric measurements. Several calibration parameters are defined which describe the state of the measurement equipment. These key parameters then form a transformational Mueller matrix which may be used to remove system bias in data received from known beacons. Several strategies are developed to quantify these time-dependent distortions for the Green Bank 140′ diameter antenna and receiver, although these methods could be applied to other similar systems. One approach quantifies the receiver biases in terms of amplitude and gain differentials. This is accomplished by measuring polarimetric differences between channels using a test signal with a known amplitude and phase. Due to variations over time periods on the scale of a beacon track, this procedure is most effective when the calibration signal is injected concurrently with the beacon measurements. To determine antenna feed distortion, including cross-polarization and ellipticity, data is recorded from an external celestial source. An example shows the effectiveness of this calibration technique by comparing calibrated data to data without correction. Error estimates of the calibration parameters in the example establish an upper bound of 0.22 TEC units for measurements at 150 MHz along track.

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Cross‐Correlation Spectropolarimetry in Single‐Dish Radio Astronomy

Cited by 22 publications

References 7 publications

A Limit on the Polarized Anomalous Microwave Emission of Lynds 1622

A Limit on the Polarized Anomalous Microwave Emission of Lynds 1622

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

Characterization of system calibration parameters for high gain dual polarization satellite beacon diagnostics of ionospheric variations

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