Single-Dish Performance of KVN 21 m Radio Telescopes: Simultaneous Observations at 22 and 43 GHz

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Abstract:We present results of long-term multi-wavelength polarization observations of the powerful blazar 3C 279 after its γ-ray flare on 2013 December 20. We followed up this flare with single-dish polarization observations using two 21-m telescopes of the Korean VLBI Network. Observations carried out weekly from 2013 December 25 to 2015 January 11, at 22 GHz, 43 GHz, 86 GHz simultaneously, as part of the Monitoring Of GAmma-ray Bright AGN (MOGABA) program. We measured 3C 279 total flux densities of 22-34 Jy at 22 GHz, 15-28 Jy (43 GHz), and 10-21 Jy (86 GHz), showing mild variability of ≤ 50 % over the period of our observations. The spectral index between 22 GHz and 86 GHz ranged from −0.13 to −0.36. Linear polarization angles were 27• -38• , 30• -42• , and 33• -50• at 22 GHz, 43 GHz, and 86 GHz, respectively. The degree of linear polarization was in the range of 6-12 %, and slightly decreased with time at all frequencies. We investigated Faraday rotation and depolarization of the polarized emission at 22-86 GHz, and found Faraday rotation measures (RM) of −300 to −1200 rad m −2 between 22 GHz and 43 GHz, and −800 to −5100 rad m −2 between 43 GHz and 86 GHz. The RM values follow a power law with a mean power law index a of 2.2, implying that the polarized emission at these frequencies travels through a Faraday screen in or near the jet. We conclude that the regions emitting polarized radio emission may be different from the region responsible for the 2013 December γ-ray flare and are maintained by the dominant magnetic field perpendicular to the direction of the radio jet at milliarcsecond scales.

Section: Observationsmentioning

confidence: 99%

Monitoring of Gamma-Ray Bright Agn: The Multi-Frequency Polarization of the Flaring Blazar 3c 279

Kang¹,

Lee²,

Byun³

2015

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“…We also performed a simultaneous multi-epoch sur Lee et al 2011). We employed 4096-channel Digital Spectrometers with a bandwidth of 32MHz each.…”

Section: Kvn 21 M Observationsmentioning

confidence: 99%

“…All the spectra were taken in the position switching mode with a total (ON+OFF) integration time of 30 minutes, yielding about 0.5 Jy rms noise levels for both transitions at velocity resolutions of 0.21 km s −1 . The KVN antennas are shaped Cassegrain type with high (∼14 dB) first sidelobe levels and the first sidelobes are separated by about 1.5 times FWHM from the primary beam center Lee et al 2011). Thus we checked whether the detected maser emission is contaminated by a nearby strong source by making a map of 1.5 FWHM×1.5 FWHM around each source in half-beam spacing.…”

Section: Kvn 21 M Observationsmentioning

confidence: 99%

Molecular Outflows From Newly Formed Massive Stars

Kim

2015

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We map 6 massive young stellar objects (YSOs) in the CO J=2-1 line and survey 18 massive YSOs, including the six, in the HCO + J=1−0, SiO J=2−1, H 2 O 6 16 − 5 23 maser, and CH 3 OH 7 0 − 6 1 A + maser lines. We detect CO bipolar outflows in all the six mapped sources. Four of them are newly discovered (07299−1651, 21306+5540, 22308+5812, 23133+6050), while 05490+2658 is mapped in the CO J=2-1 line for the first time. The detected outflows are much more massive and energetic than outflows from low-mass YSOs with masses >20 M ⊙ and momenta >300 M ⊙ km s −1 . They have mass outflow rates (3−6)×10 −4 M ⊙ yr −1 , which are at least one order of magnitude greater than those observed in low-mass YSOs. We detect HCO + and SiO line emission in 18 (100%) and 4 (22%) sources, respectively. The HCO + spectra show high-velocity wings in 11 (61%) sources. We detect H 2 O maser emission in 13 (72%) sources and 44 GHz CH 3 OH maser emission in 8 (44%) sources. Of the detected sources, 5 H 2 O and 6 CH 3 OH maser sources are new discoveries. 20081+3122 shows high-velocity (>30 km s −1 ) H 2 O maser lines. We find good correlations of the bolometric luminosity of the central (proto)star with the mechanical force, mechanical luminosity, and mass outflow rate of molecular outflow in the bolometric luminosity range of 10 −1 −10 6 L ⊙ , and identified 3 intermediate-or high-mass counterparts of Class O objects.

“…By symmetry, these arguments hold also for the case of sending waves for radar astronomy; here, usually circularly polarized radio light is used (Ostro 1993). Due to the technical simplicity of radio polarimetry, recent efforts have been directed toward simultaneous multi-wavelength polarimetry (cf., e.g., K.-T. Lee et al 2011) aimed at the measurement of differential parameters like dispersion measures.…”

Section: Radio Observationsmentioning

confidence: 99%

Polarization and Polarimetry: A Review

Trippe¹

2014

Polarization is a basic property of light and is fundamentally linked to the internal geometry of a source of radiation. Polarimetry complements photometric, spectroscopic, and imaging analyses of sources of radiation and has made possible multiple astrophysical discoveries. In this article I review (i) the physical basics of polarization: electromagnetic waves, photons, and parameterizations; (ii) astrophysical sources of polarization: scattering, synchrotron radiation, active media, and the Zeeman, GoldreichKylafis, and Hanle effects, as well as interactions between polarization and matter (like birefringence, Faraday rotation, or the Chandrasekhar-Fermi effect); (iii) observational methodology: on-sky geometry, influence of atmosphere and instrumental polarization, polarization statistics, and observational techniques for radio, optical, and X/γ wavelengths; and (iv) science cases for astronomical polarimetry: solar and stellar physics, planetary system bodies, interstellar matter, astrobiology, astronomical masers, pulsars, galactic magnetic fields, gamma-ray bursts, active galactic nuclei, and cosmic microwave background radiation.