scholarly journals 28–40 GHz variability and polarimetry of bright compact sources in the QUIJOTE cosmological fields

2021 ◽  
Vol 502 (4) ◽  
pp. 4779-4793
Author(s):  
Yvette C Perrott ◽  
Marcos López-Caniego ◽  
Ricardo T Génova-Santos ◽  
Jose Alberto Rubiño-Martín ◽  
Mark Ashdown ◽  
...  
Keyword(s):  
Point Source ◽  
Radio Frequency ◽  
Flux Density ◽  
Lognormal Distribution ◽  
Large Array ◽  
Very Large Array ◽  
Rotation Measure ◽  
Apparent Correlation ◽  
Compact Sources ◽  
Polarization Fraction

ABSTRACT We observed 51 sources in the Q-U-I JOint TEnerife (QUIJOTE) cosmological fields that were brighter than 1 Jy at 30 GHz in the Planck Point Source Catalogue (version 1), with the Very Large Array at 28–40 GHz, in order to characterize their high-radio-frequency variability and polarization properties. We find a roughly lognormal distribution of polarization fractions with a median of 2 per cent, in agreement with previous studies, and a median rotation measure (RM) of ≈1110 rad m−2 with one outlier up to ≈64 000 rad m−2, which is among the highest RMs measured in quasar cores. We find hints of a correlation between the total intensity  flux density and median polarization fraction. We find 59 per cent of sources are variable in total intensity, and 100 per cent in polarization at 3σ level, with no apparent correlation between total intensity variability and polarization variability. This indicates that it will be difficult to model these sources without simultaneous polarimetric monitoring observations and they will need to be masked for cosmological analysis.

scholarly journals WIDEBAND VERY LARGE ARRAY OBSERVATIONS OF A2256. I. CONTINUUM, ROTATION MEASURE, AND SPECTRAL IMAGING

2014 ◽  
Vol 794 (1) ◽  
pp. 24 ◽  
Author(s):  
Frazer N. Owen ◽  
Lawrence Rudnick ◽  
Jean Eilek ◽  
Urvashi Rau ◽  
Sanjay Bhatnagar ◽  
...  
Keyword(s):  
Spectral Imaging ◽  
Large Array ◽  
Very Large Array ◽  
Rotation Measure

scholarly journals Search for Extraterrestrial Intelligence at 22 GHz with the Very Large Array

2004 ◽  
Vol 213 ◽  
pp. 423-428
Author(s):  
Toshimichi Shirai ◽  
Tomoaki Oyama ◽  
Hiroshi Imai ◽  
Shinsuke Abe
Keyword(s):  
Flux Density ◽  
Direct Search ◽  
Large Array ◽  
Extraterrestrial Intelligence ◽  
Very Large Array ◽  
Exoplanetary Systems ◽  
Solar Type ◽  
Water Maser ◽  
Rule Out

We have conducted a direct Search for Extraterrestrial Intelligence at the Water Maser frequency, 22.235 GHz, using the Very Large Array. The targets were 13 solar-type stars that were known to host exoplanetary systems. In all cases, the RMS limits of the flux density, 20 mJy (5σ), were sufficient to rule out any omnidirectional transmitters of the same power as terrestrial radars (5 × 1012 W). We discuss the significance of this non-detection.

scholarly journals Particle re-acceleration and Faraday-complex structures in the RXC J1314.4-2515 galaxy cluster

2019 ◽  
Author(s):  
C Stuardi ◽  
A Bonafede ◽  
D Wittor ◽  
F Vazza ◽  
A Botteon ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Galaxy Clusters ◽  
Galaxy Cluster ◽  
Complex Structures ◽  
Very Large Array ◽  
Rotation Measure ◽  
Low Levels ◽  
Hydrodynamical Simulations ◽  
Polarization Fraction ◽  
The Magnetic Field

Abstract Radio relics are sites of electron (re)acceleration in merging galaxy clusters but the mechanism of acceleration and the topology of the magnetic field in and near relics are yet to be understood. We are carrying out an observational campaign on double relic galaxy clusters starting with RXC J1314.4-2515. With Jansky Very Large Array multi-configuration observations in the frequency range 1-4 GHz, we perform both spectral and polarization analyses, using the Rotation Measure synthesis technique. We use archival XMM-Newton observations to constrain the properties of the shocked region. We discover a possible connection between the activity of a radio galaxy and the emission of the eastern radio relic. In the northern elongated arc of the western radio relic, we detect polarized emission with an average polarization fraction of 31 % at 3 GHz and we derive the Mach number of the underlying X-ray shock. Our observations reveal low levels of fractional polarization and Faraday-complex structures in the southern region of the relic, which point to the presence of thermal gas and filamentary magnetic field morphology inside the radio emitting volume. We measured largely different Rotation Measure dispersion from the two relics. Finally, we use cosmological magneto-hydrodynamical simulations to constrain the magnetic field, viewing angle, and to derive the acceleration efficiency of the shock. We find that the polarization properties of RXC J1314.4-2515 are consistent with a radio relic observed at 70○ with respect to the line of sight and that efficient re-acceleration of fossil electrons has taken place.

scholarly journals Radio Emission from WR Stars

1982 ◽  
Vol 99 ◽  
pp. 221-224 ◽  
Author(s):  
David E. Hogg
Keyword(s):  
Simple Model ◽  
Radio Emission ◽  
Mass Loss ◽  
Flux Density ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Large Array ◽  
Radio Observations ◽  
Very Large Array

In principle radio observations of WR stars offer the best possibility of determining the rate of mass loss, since for a simple model of the extended atmosphere the mass loss rate depends primarily on quantities—the flux density, the velocity, and the distance—which are observable (Barlow 1979). Until now, detections of Wolf-Rayet stars have been limited by the sensitivity and resolution of available telescopes. The advent of the Very Large Array makes a search for emission from a large number of these stars feasible.

scholarly journals Magnetic-Field Vector Maps of Nearby Spiral Galaxies

Galaxies ◽  
2019 ◽  
Vol 7 (1) ◽  
pp. 32 ◽  
Author(s):  
Hiroyuki Nakanishi ◽  
Kohei Kurahara ◽  
Kenta Anraku
Keyword(s):  
Magnetic Field ◽  
Spiral Galaxies ◽  
Transverse Magnetic ◽  
Field Vector ◽  
Line Of Sight ◽  
Large Array ◽  
Magnetic Vector ◽  
Very Large Array ◽  
Rotation Measure ◽  
The Galaxy

We present a method for determining the directions of magnetic-field vectors in a spiral galaxy using two synchrotron polarization maps, an optical image, and a velocity field. The orientation of the transverse magnetic field is determined with a synchrotron polarization map of a higher-frequency band, and the 180 ∘ -ambiguity is solved by using a sign of Rotation Measure (RM) after determining the geometrical orientation of a disk based on an assumption of trailing spiral arms. The advantage of this method is that the direction of a magnetic vector for each line of sight throughout the galaxy can inexpensively be determined, with easily available data and simple assumptions. We applied this method to three nearby spiral galaxies using archival data obtained with a Very Large Array (VLA) to demonstrate how it works. The three galaxies have both clockwise and counterclockwise magnetic fields, which implies that none of the three galaxies is classified in a simple Axis-Symmetric type, but types of higher modes, and that magnetic reversals commonly exist.

scholarly journals A VLA Survey of Rich Clusters of Galaxies. I. Whole-cluster Maps, Source List and Source Statistics

1989 ◽  
Vol 42 (6) ◽  
pp. 633 ◽  
Author(s):  
OB Slee ◽  
RA Perley ◽  
Betty C Siegman
Keyword(s):  
Flux Density ◽  
Clusters Of Galaxies ◽  
Large Array ◽  
Spectral Indices ◽  
Cluster Radius ◽  
Very Large Array ◽  
Cluster Membership ◽  
Cluster Centre ◽  
5 Ghz

We have surveyed 58 fields near rich clusters of galaxies with the Very Large Array using scaled arrays in the B/C and/or C/O configurations at 1�5 GHz and 4�9 GHz. The fields were centred on steep spectrum sources in or near clusters that were earlier surveyed with lower resolution telescopes. The whole-field maps at 1�5 GHz are given and a list of 940 sources with 1�5 GHz flux densities down to -1 mJy is presented. Spectral indices of sources within 5' of the field centres are given. Complete flux-limited samples of sources are used to establish a criterion for cluster membership. Sources with total 1�5 GHz flux density >20 mjy and closer to the cluster centre than 0�28 of the cluster radius (a total of 57 sources) are accepted as cluster members.

scholarly journals Jupiter’s Synchrotron Radiation Throughout the Comet P/Shoemaker-Levy 9 Impact Period

1995 ◽  
Vol 10 ◽  
pp. 637-638
Author(s):  
I. de Pater ◽  
C. Heiles ◽  
M. Wong ◽  
R.J. Maddalena ◽  
M.K. Bird ◽  
...  
Keyword(s):  
Synchrotron Radiation ◽  
Flux Density ◽  
Radio Spectrum ◽  
Brightness Distribution ◽  
Microwave Emission ◽  
Central Meridian ◽  
Large Array ◽  
Very Large Array ◽  
Particle Population

Jupiter’s microwave emission was observed throughout the SL9 impact period by many different telescopes, among which the NRAO 140-foot telescope in Green Bank (21 cm), Westerbork (92 cm), Effelsberg (6, 11 cm), Parkes (21 cm), NASA DSN (13 cm), and the Very Large Array (22, 90 cm). We determined the “average” total nonthermal flux density from the planet after having subtracted the thermal contribution, following the formulation by de Pater and Klein, (1989) and Klein et al., (1989). The flux density increased typically by 40-50% at 6 cm wavelength, 27% at 11-13 cm, 22%at 21 cm and 10-15% at 90 cm. Thus the radio spectrum hardened considerably during the week of cometary impacts. Following the week of cometary impacts, the flux density began to subside at all wavelength.VLA images show the brightness distribution of the planet; a comparison of images taken before and during the week of impacts show marked changes in the brightness distribution. At a central meridian longitude λIII≈ 110°, the left side of the belts increased considerably and moved inwards by ~ 0.2 RJ. This suggests that the increase in flux density is caused by energization of the resident particle population.

scholarly journals Probing the non-thermal emission in the Perseus cluster with the JVLA

2018 ◽  
Vol 14 (S342) ◽  
pp. 44-52
Author(s):  
M. Gendron-Marsolais ◽  
J. Hlavacek-Larrondo ◽  
R. J. van Weeren ◽  
T. Clarke ◽  
A. C. Fabian ◽  
...  
Keyword(s):  
Radio Frequency ◽  
Thermal Emission ◽  
Large Array ◽  
High Quality ◽  
Filamentary Structure ◽  
Very Large Array ◽  
Particle Population ◽  
Core Cluster ◽  
Radio Frequencies ◽  
Perseus Cluster

AbstractWe present deep low radio frequency (230-470 MHz) observations from the Karl G. Jansky Very Large Array of the Perseus cluster, probing the non-thermal emission from the old particle population of the AGN outflows. Our observations of this nearby relaxed cool core cluster have revealed a multitude of new structures associated with the mini-halo, extending to hundreds of kpc in size. Its irregular morphology seems to have been influenced both by the AGN activity and by the sloshing motion of the cluster’ gas. In addition, it has a filamentary structure similar to that seen in radio relics found in merging clusters. These results illustrate the high-quality images that can be obtained with the new JVLA at low radio-frequencies.

scholarly journals Radio emission in ultracool dwarfs: The nearby substellar triple system VHS 1256–1257

2018 ◽  
Vol 610 ◽  
pp. A23 ◽  
Author(s):  
J. C. Guirado ◽  
R. Azulay ◽  
B. Gauza ◽  
M. A. Pérez-Torres ◽  
R. Rebolo ◽  
...  
Keyword(s):  
Radio Emission ◽  
Flux Density ◽  
Upper Bound ◽  
Equal Mass ◽  
Large Array ◽  
Turnover Frequency ◽  
Radio Flux ◽  
Very Large Array ◽  
Upper Limit ◽  
Low Mass

Aim. With the purpose of investigating the radio emission of new ultracool objects, we carried out a targeted search in the recently discovered system VHS J125601.92–125723.9 (hereafter VHS 1256–1257); this system is composed by an equal-mass M7.5 binary and a L7 low-mass substellar object located at only 15.8 pc. Methods. We observed in phase-reference mode the system VHS 1256–1257 with the Karl G. Jansky Very Large Array at X band and L band and with the European VLBI Network at L band in several epochs during 2015 and 2016. Results. We discovered radio emission at X band spatially coincident with the equal-mass M7.5 binary with a flux density of 60 μJy. We determined a spectral index α = −1.1 ± 0.3 between 8 and 12 GHz, suggesting that non-thermal, optically thin, synchrotron, or gyrosynchrotron radiation is responsible for the observed radio emission. Interestingly, no signal is seen at L band where we set a 3σ upper limit of 20 μJy. This might be explained by strong variability of the binary or self-absorption at this frequency. By adopting the latter scenario and gyrosynchrotron radiation, we constrain the turnover frequency to be in the interval 5–8.5 GHz, from which we infer the presence of kG-intense magnetic fields in the M7.5 binary. Our data impose a 3σ upper bound to the radio flux density of the L7 object of 9 μJy at 10 GHz.

scholarly journals MODELING THE MAGNETIC FIELD IN THE GALACTIC DISK USING NEW ROTATION MEASURE OBSERVATIONS FROM THE VERY LARGE ARRAY

2011 ◽  
Vol 728 (2) ◽  
pp. 97 ◽  
Author(s):  
C. L. Van Eck ◽  
J. C. Brown ◽  
J. M. Stil ◽  
K. Rae ◽  
S. A. Mao ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Galactic Disk ◽  
Large Array ◽  
Very Large Array ◽  
Rotation Measure ◽  
The Magnetic Field
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