Software Polarization Spectrometer "PolariS"

We have developed a software-based polarization spectrometer, PolariS, to acquire full-Stokes spectra with a very high spectral resolution of 61 Hz. The primary aim of PolariS is to measure the magnetic fields in dense star-forming cores by detecting the Zeeman splitting of molecular emission lines. The spectrometer consists of a commercially available digital sampler and a Linux computer. The computer is equipped with a graphics processing unit (GPU) to process FFT and cross-correlation using the Compute Unified Device Architecture (CUDA) library developed by NVIDIA. Thanks to a high degree of precision in quantization of the analog-to-digital converter and arithmetic in the GPU, PolariS offers excellent performances in linearity, dynamic range, sensitivity, bandpass flatness and stability. The software has been released under the MIT License and is available to the public. In this paper, we report the design of PolariS and its performance verified through engineering tests and commissioning observations.

[1]  Ray P. Norris,et al.  MERLIN observations of OH maser outflows in Orion–KL , 1984 .

[2]  Yasuo Fukui,et al.  A Complete Search for Dense Cloud Cores in Taurus , 2002 .

[3]  Alyssa A. Goodman,et al.  Measurement of Magnetic Field Strength in the Dark Cloud Barnard 1 , 1989 .

[4]  Ray P. Norris,et al.  MERLIN observations of OH outflow in W75N , 1986 .

[5]  C. Heiles,et al.  Interstellar Magnetic Field Strengths and Gas Densities: Observational and Theoretical Perspectives , 1986 .

[6]  Helmut Wiesemeyer,et al.  XPOL—the Correlation Polarimeter at the IRAM 30-m Telescope , 2008, 0806.1666.

[7]  G. Swenson,et al.  Interferometry and Synthesis in Radio Astronomy , 2017, 1708.09761.

[8]  Masatoshi Ohishi,et al.  A survey of CCS, HC3N, HC5N, and NH3 toward dark cloud cores and their production chemistry , 1992 .

[9]  James M. Moran,et al.  The structure of interstellar hydroxyl masers: VLBI synthesis observations of W3(OH) , 1980 .

[10]  Alyssa A. Goodman,et al.  OH Zeeman observations of dark clouds , 1993 .

[11]  Hiroko Shinnaga,et al.  Zeeman Effect on the Rotational Levels of CCS and SO in the 3Σ- Ground State , 2000 .

[12]  William D. Langer,et al.  Low-Mass Clumps in TMC-1: Scaling Laws in the Small-Scale Regime , 1998 .

[13]  Stephanie Thalberg,et al.  Interferometry And Synthesis In Radio Astronomy , 2016 .

[14]  Ralph A. Gaume,et al.  A study of the ground-state hydroxyl maser emission associated with 11 regions of star formation , 1987 .

[15]  Stefano Salvini,et al.  Real-time, fast radio transient searches with GPU de-dispersion , 2011, 1107.2516.

[16]  Hiroshi Imai,et al.  Optimization by Smoothed Bandpass Calibration in Radio Spectroscopy , 2012, 1205.3889.

[17]  James M. Moran,et al.  Evidence for Zeeman Splitting in 1720 MHz OH Line Emission (9) , 1975 .

[18]  F. Adams,et al.  Star Formation in Molecular Clouds: Observation and Theory , 1987 .

[19]  Christopher J. Fluke,et al.  Accelerating incoherent dedispersion , 2012, 1201.5380.

[20]  Seiji Kameno,et al.  A New System Noise Measuring Method Using a 2-Bit Analog-to-Digital Converter , 2010 .

[21]  R. Davies,et al.  Astronomical Society of the Pacific Conference Series , 2010 .

[22]  Richard M. Crutcher,et al.  Detection of the CN Zeeman Effect in Molecular Clouds , 1999 .