Subarcminute resolution imaging of radio sources at 74 MHz with the Very Large Array

1993 ◽  
Vol 106 ◽  
pp. 2218 ◽  
Author(s):  
N. E. Kassim ◽  
R. A. Perley ◽  
W. C. Erickson ◽  
K. S. Dwarakanath
Keyword(s):  
Radio Sources ◽  
Large Array ◽  
Very Large Array ◽  
Resolution Imaging

scholarly journals Comparison of the Optical and Radio Reference Frames

1986 ◽  
Vol 7 ◽  
pp. 103-108 ◽  
Author(s):  
K. J. Johnston ◽  
Chr. de Vegt
Keyword(s):  
Radio Emission ◽  
Reference Frame ◽  
Radio Telescope ◽  
Reference Frames ◽  
Radio Sources ◽  
Large Array ◽  
Very Large Array ◽  
Extragalactic Radio Sources ◽  
Optical Reference ◽  
Lack Of Knowledge

The Very Large Array (VLA) has made possible the measurement of the precise positions of the radio emission associated with stars. This allows the direct comparison of the optical reference frame (FK4) with the radio reference frame which is defined by the quasi-absolute positions of extragalactic radio sources. This comparison is limited by the small number of bright stars that display detectable radio emission and the lack of knowledge of the precise coincidence of the radio emission with the optical photocenter of the star. Since the VLA is the most sensitive astrometrically capable radio telescope, positions of the largest number of stars north of declination -20 degrees can be measured. The accuracy of the positions on the extragalactic reference frame should approach a milliarcsecond.

scholarly journals EXPLORING THE NATURE OF COMPACT RADIO SOURCES ASSOCIATED TO UCHII REGIONS

2021 ◽  
Vol 57 (1) ◽  
pp. 81-89
Author(s):  
J. M. Masqué ◽  
L. F. Rodríguez ◽  
S. A. Dzib ◽  
S. N. Medina ◽  
L. Loinard ◽  
...  
Keyword(s):  
Massive Star ◽  
Thermal Emission ◽  
Hii Regions ◽  
Radio Sources ◽  
Large Array ◽  
Gravitational Radius ◽  
Very Large Array ◽  
Thermal Sources

We present Very Large Array 7 mm continuum observations of four ultracompact (UC) HII regions, observed previously at 1.3 cm, in order to investigate the nature of the compact radio sources associated with these regions. We detect a total of seven compact radio sources, four of them with thermal emission, and two compact radio sources with clear non- thermal emission. The thermal emission is consistent with the presence of an ionized envelope, either static (i.e., trapped in the gravitational radius of an associated massive star) or flowing away (i.e., a photo-evaporative flow). The nature of the non-thermal sources remains unclear and several possibilities are proposed. The possibility that most of these compact radio sources are photo-evaporating objects, and the remaining ones more evolved objects, is consistent with previous studies on UCHII regions.

scholarly journals VERY LARGE ARRAY AND JANSKY VERY LARGE ARRAY OBSERVATIONS OF THE COMPACT RADIO SOURCES IN M8

2014 ◽  
Vol 797 (1) ◽  
pp. 60 ◽  
Author(s):  
Josep M. Masqué ◽  
Sergio Dzib ◽  
Luis F. Rodríguez
Keyword(s):  
Radio Sources ◽  
Large Array ◽  
Very Large Array

scholarly journals On the nature of infrared-faint radio sources in the Subaru X-ray Deep and Very Large Array–VIMOS VLT Deep Survey fields

2017 ◽  
Vol 470 (4) ◽  
pp. 4956-4973 ◽  
Author(s):  
Veeresh Singh ◽  
Yogesh Wadadekar ◽  
C. H. Ishwara-Chandra ◽  
Sandeep Sirothia ◽  
Jonathan Sievers ◽  
...  
Keyword(s):  
Radio Sources ◽  
Large Array ◽  
Very Large Array ◽  
X Ray ◽  
Deep Survey

scholarly journals Unveiling the cause of hybrid morphology radio sources (HyMoRS)

2019 ◽  
Vol 491 (1) ◽  
pp. 803-822 ◽  
Author(s):  
Jeremy J Harwood ◽  
Tessa Vernstrom ◽  
Andra Stroe
Keyword(s):  
Radio Galaxies ◽  
Core Region ◽  
Line Of Sight ◽  
Radio Sources ◽  
Large Array ◽  
Very Large Array ◽  
Array Configuration ◽  
The Core ◽  
Vlbi Observations ◽  
Rare Group

ABSTRACT Hybrid morphology radio sources (HyMoRS) are a rare group of radio galaxies in which differing Fanaroff & Riley morphologies (FR I/II) are observed for each of the two lobes. While they potentially provide insights into the formation of lobe structure, particle acceleration, and the FR dichotomy, previous work on HyMoRS has mainly been limited to low-resolution studies, searches for new candidates, and milliarcsecond-scale VLBI observations of the core region. In this paper, we use new multi-array configuration Very Large Array (VLA) observations between 1 and 8 GHz to determine the morphology of HyMoRS on arcsecond scales and perform the first well-resolved spectral study of these unusual sources. We find that while the apparent FR I lobe is centre brightened, this is the result of a compact acceleration region resembling a hotspot with a spectrum more consistent with an FR II (‘strong-flavour’) jet. We find that the spectra of the apparent FR I lobes are not similar to their classical counterparts and are likely the result of line-of-sight mixing of plasma across a range of spectral ages. We consider possible mechanisms that could lead to the formation of HyMoRS under such conditions, including environment asymmetry and restarted sources, concluding through the use of simple modelling that HyMoRS are the result of orientation effects on intrinsically FR II sources with lobes non-parallel to the inner jet.

VLA Observations of Angular Broadening Close to the Sun

2001 ◽  
Vol 182 ◽  
pp. 193-196
Author(s):  
Pradeep Gothoskar ◽  
K.R. Anantharamahaia ◽  
Ketan Desai ◽  
A.P. Rao
Keyword(s):  
Magnetic Fields ◽  
Solar Minimum ◽  
Radial Direction ◽  
Anisotropic Scattering ◽  
Radio Sources ◽  
The Sun ◽  
Large Array ◽  
Very Large Array ◽  
Radio Frequencies

AbstractWe present synthesis imaging of scatter-broadening of radio sources carried out using the Very Large Array (VLA) at six radio frequencies during the period of solar minimum. Three compact radio sources were observed from 2 to 16 solar radii around the sun. The data indicate highly anisotropic scattering. The scatter-broadening was estimated from the area of the scattered image and was found to be factor of two lower and orientation of magnetic fields was closer to the radial direction. Present observations confirm the variation of scatter-broadening with solar elongation.

scholarly journals 20cm VLA radio-continuum study of M31: Images and point source catalogues

2012 ◽  
pp. 41-68 ◽  
Author(s):  
T.J. Galvin ◽  
M.D. Filipovic ◽  
E.J. Crawford ◽  
N.F.H. Tothill ◽  
G.F. Wong ◽  
...  
Keyword(s):  
High Resolution ◽  
Angular Resolution ◽  
High Sensitivity ◽  
Radio Continuum ◽  
High Angular Resolution ◽  
Radio Sources ◽  
Large Array ◽  
Complete Sample ◽  
Very Large Array ◽  
Discrete Radio Sources

We present a series of new high-sensitivity and high-resolution radio-continuum images of M31 at ?=20 cm (?=1.4 GHz). These new images were produced by merging archived 20 cm radio-continuum observations from the Very Large Array (VLA) telescope. Images presented here are sensitive to rms=60 ?Jy and feature high angular resolution (<10??). A complete sample of discrete radio sources have been catalogued and analyzed across 17 individual VLA projects. We identified a total of 864 unique discrete radio sources across the field of M31. One of the most prominent regions in M31 is the ring feature for which we estimated total integrated flux of 706 mJy at ?=20 cm. We compare here detected sources to those listed in Gelfand et al. (2004) at ?=92 cm and find 118 sources in common to both surveys. The majority (61%) of these sources exhibit a spectral index of ? <-0.6 indicating that their emission is predominantly non-thermal in nature, that is more typical for background objects.

scholarly journals What are “X-shaped” Radio Sources Telling Us? I. Very Large Array Imaging of a Large Sample of Candidate XRGs

2018 ◽  
Vol 852 (1) ◽  
pp. 47 ◽  
Author(s):  
David H. Roberts ◽  
Lakshmi Saripalli ◽  
Kevin X. Wang ◽  
Mayuri Sathyanarayana Rao ◽  
Ravi Subrahmanyan ◽  
...  
Keyword(s):  
Radio Sources ◽  
Large Array ◽  
Very Large Array ◽  
Large Sample ◽  
Array Imaging

Multiwavelength analysis of OH Megamaser galaxies: The case of IRAS11506-3851

2020 ◽  
Vol 15 (S359) ◽  
pp. 347-349
Author(s):  
Carpes P. Hekatelyne ◽  
Thaisa Storchi-Bergmann
Keyword(s):  
Active Galactic Nuclei ◽  
Hubble Space Telescope ◽  
Galactic Nuclei ◽  
Large Array ◽  
Very Large Array ◽  
Star Forming ◽  
Star Forming Regions ◽  
Field Unit ◽  
Mixed Transition ◽  
Integral Field

AbstractWe present Multi-Object Spectrograph (GMOS) Integral Field Unit (IFU), Hubble Space Telescope (HST) and Very Large Array (VLA) observations of the inner kpc of the OH Megamaser galaxy IRAS 11506-3851. In this work we discuss the kinematics and excitation of the gas as well as its radio emission. The HST images reveal an isolated spiral galaxy and the combination with the GMOS-IFU flux distributions allowed us to identify a partial ring of star-forming regions surrounding the nucleus with a radius of ≍500 pc. The emission-line ratios and excitation map reveal that the region inside the ring present mixed/transition excitation between those of Starbursts and Active Galactic Nuclei (AGN), while regions along the ring are excited by Starbursts. We suggest that we are probing a buried or fading AGN that could be both exciting the gas and originating an outflow.

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