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 Quasi-simultaneous Radio/X-Ray Observations of the Candidate Transitional Millisecond Pulsar 3FGL J1544.6−1125 during its Low-luminosity Accretion-disk State

2021 ◽  
Vol 923 (1) ◽  
pp. 3
Author(s):  
Amruta D. Jaodand ◽  
Adam T. Deller ◽  
Nina Gusinskaia ◽  
Jason W. T. Hessels ◽  
James C. A. Miller-Jones ◽  
...  
Keyword(s):  
Accretion Disk ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Large Array ◽  
Millisecond Pulsar ◽  
Very Large Array ◽  
X Ray ◽  
Upper Limit ◽  
5 Ghz ◽  
Variable Radio

Abstract 3FGL J1544.6−1125 is a candidate transitional millisecond pulsar (tMSP). Similar to the well-established tMSPs—PSR J1023+0038, IGR J18245−2452, and XSS J12270−4859—3FGL J1544.6−1125 shows γ-ray emission and discrete X-ray “low” and “high” modes during its low-luminosity accretion-disk state. Coordinated radio/X-ray observations of PSR J1023+0038 in its current low-luminosity accretion-disk state showed rapidly variable radio continuum emission—possibly originating from a compact, self-absorbed jet, the “propellering” of accretion material, and/or pulsar moding. 3FGL J1544.6−1125 is currently the only other (candidate) tMSP system in this state, and can be studied to see whether tMSPs are typically radio-loud compared to other neutron star binaries. In this work, we present a quasi-simultaneous Very Large Array and Swift radio/X-ray campaign on 3FGL J1544.6−1125. We detect 10 GHz radio emission varying in flux density from 47.7 ± 6.0 μJy down to ≲15 μJy (3σ upper limit) at four epochs spanning three weeks. At the brightest epoch, the radio luminosity is L 5 GHz = (2.17 ± 0.17) × 1027 erg s−1 for a quasi-simultaneous X-ray luminosity L 2–10 keV = (4.32 ± 0.23) × 1033 erg s−1 (for an assumed distance of 3.8 kpc). These luminosities are close to those of PSR J1023+0038, and the results strengthen the case that 3FGL J1544.6−1125 is a tMSP showing similar phenomenology to PSR J1023+0038.

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 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 VLA Observations of Nine Extended Green Objects in the Milky Way: Ubiquitous Weak, Compact Continuum Emission, and Multi-epoch Emission from Methanol, Water, and Ammonia Masers

2021 ◽  
Vol 923 (2) ◽  
pp. 263
Author(s):  
A. P. M. Towner ◽  
C. L. Brogan ◽  
T. R. Hunter ◽  
C. J. Cyganowski
Keyword(s):  
Milky Way ◽  
Thermal Emission ◽  
Young Stellar Objects ◽  
Continuum Emission ◽  
Large Array ◽  
Spectral Indices ◽  
Physical Processes ◽  
Stellar Objects ◽  
Maser Emission ◽  
Very Large Array

Abstract We have observed a sample of nine Extended Green Objects (EGOs) at 1.3 and 5 cm with the Very Large Array (VLA) with subarcsecond resolution and ∼7–14 μJy beam−1-sensitivities in order to characterize centimeter continuum emission as it first appears in these massive protoclusters. We find an EGO-associated continu um emission—within 1″ of the extended 4.5 μm emission—in every field, which is typically faint (order 101–102 μJy) and compact (unresolved at 0″.3–0″.5). The derived spectral indices of our 36 total detections are consistent with a wide array of physical processes, including both non-thermal (19% of detections) and thermal free–free processes (e.g., ionized jets and compact H ii regions, 78% of sample) and warm dust (1 source). We also find an EGO-associated 6.7 GHz CH3OH and 22 GHz H2O maser emission in 100% of the sample and a NH3 (3,3) masers in ∼45%; we do not detect any NH3 (6,6) masers at ∼5.6 mJy beam−1 sensitivity. We find statistically-significant correlations between L radio and L bol at two physical scales and three frequencies, consistent with thermal emission from ionized jets, but no correlation between L H 2 O and L radio for our sample. From these data, we conclude that EGOs likely host multiple different centimeter continuum-producing processes simultaneously. Additionally, at our ∼1000 au resolution, we find that all EGOs except G18.89−0.47 contain 1 ∼ 2 massive sources based on the presence of CH3OH maser groups, which is consistent with our previous work suggesting that these are typical massive protoclusters, in which only one to a few of the young stellar objects are massive.

scholarly journals A VERY LARGE ARRAY SEARCH FOR 5 GHz RADIO TRANSIENTS AND VARIABLES AT LOW GALACTIC LATITUDES

2011 ◽  
Vol 740 (2) ◽  
pp. 65 ◽  
Author(s):  
E. O. Ofek ◽  
D. A. Frail ◽  
B. Breslauer ◽  
S. R. Kulkarni ◽  
P. Chandra ◽  
...  
Keyword(s):  
Large Array ◽  
Very Large Array ◽  
Radio Transients ◽  
5 Ghz

scholarly journals A VLA Survey of Rich Clusters of Galaxies II. The Stronger Sources: Maps, Polarisations and Identifications

1994 ◽  
Vol 47 (2) ◽  
pp. 145 ◽  
Author(s):  
OB Slee ◽  
AL Roy ◽  
Ann Savage
Keyword(s):  
Flux Density ◽  
Source Parameters ◽  
Angular Size ◽  
Optical Parameters ◽  
Radio Sources ◽  
Very Large Array ◽  
Contour Maps ◽  
Optical Images ◽  
5 Ghz ◽  
Linear Polarisation

We present detailed radio and optical parameters for the stronger radio sources in 58 Abell cluster fields observed with the Very Large Array (VLA) using scaled arrays at 1�5 and 4�9 GHz. These sources comprise a complete sample with 1� 5 GHz flux density :;::20 mJy and cover a combined sky area of 3�5 X 10-5 sr. The cluster fields were distributed over 24 h of RA and between declinations +350 and -300 Contour maps at two frequencies are presented and source parameters such as position, angular size, spectral index, linear polarisation and core flux density are tabulated. We also derive the emitted power and linear size for those sources close to the cluster centres and therefore highly likely to be cluster members. We attempt to identify all these radio sources with optical images on the Palomar and SERC survey plates and give their accurate optical coordinates, morphologies and apparent magnitudes.

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.

Powerful Radio Sources in Clusters of Galaxies

1991 ◽  
Vol 9 (1) ◽  
pp. 100-102
Author(s):  
A. M. Unewisse ◽  
R. W. Hunstead
Keyword(s):  
Radio Emission ◽  
Radio Source ◽  
Flux Density ◽  
Radio Sources ◽  
High Flux ◽  
Clusters Of Galaxies ◽  
Powerful Radio ◽  
Complete Sample ◽  
Cluster Galaxies ◽  
Cluster Centre

AbstractUsing a complete sample, we have looked for correlations in position between radio sources with S408 ≥ 1 Jy in the Molonglo Reference Catalogue (MRC) and rich clusters of galaxies in the Abell, Corwin and Olowin catalogue (ACO). Within a projected radius of 100 kpc of the cluster centre, we find an overdensity of radio sources similar to that seen by Robertson and Roach (1990). They attributed this feature to centrally located dominant cluster galaxies. We confirm this hypothesis by looking at the morphology of the clusters within this peak and by optically identifying galaxies associated with the radio emission. Due to the relatively high flux density limit imposed, the cluster radio sources in this sample are among the most powerful in the southern sky. The probability of a cluster containing a radio source of this power is found not to depend on cluster richness.

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 Radio-emitting narrow-line Seyfert 1 galaxies in the JVLA perspective

2018 ◽  
Vol 614 ◽  
pp. A87 ◽  
Author(s):  
M. Berton ◽  
E. Congiu ◽  
E. Järvelä ◽  
R. Antonucci ◽  
P. Kharb ◽  
...  
Keyword(s):  
Radio Continuum ◽  
Large Array ◽  
Narrow Line ◽  
Diffuse Emission ◽  
Parent Population ◽  
Very Large Array ◽  
General Properties ◽  
Spectrum Radio ◽  
First Results ◽  
5 Ghz

We report the first results of a survey on 74 narrow-line Seyfert 1 galaxies (NLS1s) carried out in 2015 with the Karl G. Jansky Very Large Array (JVLA) at 5 GHz in A-configuration. So far, this is the largest survey aimed to image the radio continuum of NLS1s. We produced radio maps in order to compare the general properties of three different samples of objects: radio-quiet NLS1s (RQNLS1s), steep-spectrum radio-loud NLS1s (S-NLS1s), and flat-spectrum radio-loud NLS1s (F-NLS1s). We find that the three classes correspond to different radio morphologies, with F-NLS1s being more compact, and RQNLS1s often showing diffuse emission on kpc scales. We also find that F-NLS1s might be low-luminosity and possibly young blazars, and that S-NLS1s are part of the parent population of F-NLS1s. Dedicated studies to RQNLS1s are needed to fully understand their role in the unification pictures.

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