Observations of sources of maser radio emission having an angular resolution of 0.2 msec of arc

1973 ◽  
Vol 16 (5) ◽  
pp. 613-616 ◽  
Author(s):  
B. F. Burke ◽  
K. D. Johnston ◽  
V. A. Efanov ◽  
B. D. Clark ◽  
L. R. Kogan ◽  
...  
Keyword(s):  
Radio Emission ◽  
Angular Resolution ◽  
Maser Radio

scholarly journals Radio Continuum Surveys of the Galaxy and Galaxies

2002 ◽  
Vol 199 ◽  
pp. 262-267
Author(s):  
Richard Wielebinski
Keyword(s):  
Magnetic Fields ◽  
Radio Emission ◽  
Linear Polarization ◽  
Angular Resolution ◽  
Low Frequency ◽  
Radio Continuum ◽  
Sky Surveys ◽  
The Galaxy ◽  
Nearby Galaxies ◽  
Radio Frequencies

Radio sky surveys give us basic information about the origin of the radio emission from the Galaxy. By mapping the sky at several radio frequencies a separation of the thermal and non-thermal emission components is possible. The major part of the low-frequency radio emission comes from the synchrotron process, the braking of relativistic electrons in magnetic fields. By mapping the linear polarization at several frequencies (required for the correction of the Faraday rotation) the orientation of the magnetic fields in the emitting regions can be deduced. Older all-sky surveys at 30, 150 and 408 MHz have now been supplemented by new observations of the Galaxy at 45 and 1420 MHz. These surveys, in addition to being important as tracers of the morphology of the magnetic fields in the Galaxy, are also required to correct for the ‘foreground’ features in cosmological studies of the COBE data and the PLANCK surveys in the future. Studies of the Galaxy in polarization have been made some years ago indicating high percentage of linear polarization in various directions. More recent work with good angular resolution has shown spectacular polarized intensity structures in selected regions. Low-frequency data with good angular resolution are urgently required for the interpretation of these features.Observations of nearby galaxies in radio continuum (both total power and polarized intensity) have given us the possibility to study magnetic fields in objects at known distances. Polarization observations of nearby galaxies have confirmed the existence of regular magnetic fields in practically every object so far studied. Originally data were obtained from large single-dish telescopes, notably from Effelsberg and Parkes. These data were greatly enhanced by the addition of higher resolution components from the VLA and ATCA respectively. These results indicate surprisingly homogeneous magnetic fields in most galaxies. High angular resolution observations with the GMRT at lower radio frequencies will add a new dimension to the data on galaxies.

scholarly journals A Pilot Radio Search for Magnetic Activity in Directly Imaged Exoplanets

2021 ◽  
Vol 163 (1) ◽  
pp. 15
Author(s):  
Y. Cendes ◽  
P. K. G. Williams ◽  
E. Berger
Keyword(s):  
Pilot Study ◽  
Radio Emission ◽  
Angular Resolution ◽  
Magnetic Activity ◽  
Systematic Search ◽  
Archival Data ◽  
Large Array ◽  
Very Large Array ◽  
Upper Limits ◽  
Host Stars

Abstract We present the first systematic search for GHz frequency radio emission from directly imaged exoplanets using Very Large Array observations of sufficient angular resolution to separate the planets from their host stars. We obtained results for five systems and eight exoplanets located at ≲50 pc through new observations (Ross 458, GU Psc, and 51 Eri) and archival data (GJ 504 and HR 8799). We do not detect radio emission from any of the exoplanets, with 3σ luminosity upper limits of (0.9–23) × 1021 erg s−1. These limits are comparable to the level of radio emission detected in several ultracool dwarfs, including T dwarfs, whose masses are only a factor of two times higher than those of the directly imaged exoplanets. Despite the lack of detections in this pilot study, we highlight the need for continued GHz frequency radio observations of nearby exoplanets at μJy-level sensitivity.

High-Resolution Observations of Centaurus-A and Pictor-A at 160 MHz

1975 ◽  
Vol 2 (6) ◽  
pp. 336-338 ◽  
Author(s):  
O.B. Slee ◽  
K.V. Sheridan
Keyword(s):  
High Resolution ◽  
Radio Emission ◽  
Energy Distribution ◽  
High Frequency ◽  
Angular Resolution ◽  
Radio Galaxies ◽  
Relativistic Electrons ◽  
Frequency Measurements ◽  
Centaurus A

Since early 1974 the radioheliograph operated by the Division of Radiophysics at Culgoora, N.S.W. has been used in a 160 MHz study of ~2000 catalogued sources in the declination range -46° to +35°. In addition to measurements of flux densities and accurate positions at 160 MHz, brightness distributions are obtained for the sources that can be resolved by the 1’.9 × 1’.9 arc beams. A comparison of the brightness distributions at 160 MHz with those obtained from high-frequency measurements with similar angular resolution can yield valuable information about the energy distribution of the relativistic electrons, which are believed to be responsible for the radio emission from most nonthermal sources. Among the first objects to be examined were the strong southern radio galaxies Centaurus-A and Pictor-A.

scholarly journals History of the Light Curves and Molecular Maser Emission of the Miras U Ori and R Leo

1993 ◽  
Vol 155 ◽  
pp. 323-323
Author(s):  
I. L. Andronov ◽  
L. S. Kudashkina ◽  
G. M. Rudnitskij
Keyword(s):  
Radio Emission ◽  
Molecular Species ◽  
Light Curves ◽  
Evolutionary Status ◽  
Maser Emission ◽  
Radio Line ◽  
History Of ◽  
Maser Radio

We have collected all the available data on light curves, OH, H2O and SiO maser observations for a sample of Mira-type variables. We consider in detail the data on two stars, U Ori and R Leo. There is a net correlation between optical and radio line variations for all the three molecular species in these stars. More pronounced maser flares seem to follow brighter-than-average visual maxima of the stars. We discuss also the drastic changes in the type of the OH maser radio emission which happened in these stars some years ago. Implications for the mechanisms of maser pumping and the evolutionary status of these stars (probably undergoing the helium flash) are discussed.

Design and development of a two-dish interferometer

2019 ◽  
Vol 15 (S356) ◽  
pp. 408-408
Author(s):  
Dorcus Mulumba
Keyword(s):  
Radio Emission ◽  
Radio Astronomy ◽  
Engineering Students ◽  
Angular Resolution ◽  
High Sensitivity ◽  
Separation Distance ◽  
Radio Interferometry ◽  
Parabolic Dish ◽  
Target Source ◽  
Local Interference

AbstractThe angular resolution and the sensitivity of a parabolic dish telescope increase with the diameter of its aperture at a given frequency. This implies that as the telescope gets larger, its resolution becomes better. However, constructing telescopes of ever increasing size is prohibitive for both technical and financial reasons. This problem is solved by using an interferometer which consists of two or more separate telescopes that combine their signals offering a resolution equivalent to the largest separation distance between the telescopes. In this work, the electric field variations from two telescopes will be obtained. The voltage signals from the two telescopes will be coherently combined in order to derive the structure of the target source of radio emission. This combination will be done by a cross-correlator, which multiplies and averages the voltage outputs V1 and V2 of the two dishes. A major challenge to be addressed in this work is to design an instrument capable of making professional-type radio astronomy measurement in a local interference environment. In this regard, the investigative part of this work will verify whether it is possible to achieve a high sensitivity enough to detect some cosmic sources where the presence of man-made interference and cost adversely influences the system. The design of an interferometer will be presented and implemented. It may also serve as a demonstrator for engineering students to gain a working knowledge of radio interferometry.

scholarly journals Old Supernova Remnants: Structure and Source of Radio Emission

1987 ◽  
Vol 40 (6) ◽  
pp. 713 ◽  
Author(s):  
AP Glushak ◽  
AV Kovalenko ◽  
SM Kutuzov ◽  
AV Pynzar' ◽  
VA Udal’tsov
Keyword(s):  
Radio Emission ◽  
Supernova Remnants ◽  
Angular Resolution ◽  
Angular Size ◽  
Cosmic Ray ◽  
Lebedev Physical Institute ◽  
Physical Institute ◽  
Contour Maps ◽  
Lebedev Physical

Contour maps at 102· 5 MHz for 12 galactic SNRs of large angular size in the northern sky are presented. The observations were made with an angular resolution of 48' x24' sec(55° - 8) using the BSA telescope of the Lebedev Physical Institute. All sources were mapped in total intensity. Our results indicate that the contribution to the radiation of observed SNRs from swept up cosmic ray electrons is small. The characteristics of the observed sources are discussed.

scholarly journals Unusual Radio Structures in Markarian 6

1996 ◽  
Vol 175 ◽  
pp. 177-178
Author(s):  
M.J. Kukula ◽  
A. Pedlar ◽  
S.A. Baum ◽  
A.J. Holloway
Keyword(s):  
Radio Emission ◽  
Radio Telescope ◽  
Angular Resolution ◽  
Seyfert Galaxy ◽  
Narrow Line ◽  
Line Region ◽  
Typical Distances ◽  
Narrow Line Region

Markarian 6, a Seyfert Galaxy of type 1.5, is one of several Seyfert nuclei to be observed with MERLIN at 6 and 18 cm as part of a project to investigate the radio structures of these objects on sub–arcsecond scales (corresponding to scales of a few tens of parsecs at typical distances). The angular resolution of MERLIN at 6 cm is equivalent to that of the HST, making the radio images ideal for comparison with HST images of the optical Narrow–Line Region (NLR). In this paper we briefly discuss the results of our MERLIN observations of Markarian 6, along with a 6–cm Westerbork Synthesis Radio Telescope (WSRT) map of the arcsecond (kpc) scale radio emission. The data is discussed in more detail by Kukula et al. (1996) and Baum et al. (1993).

scholarly journals J1615+5452: a remnant radio galaxy in the ELAIS-N1 field

2020 ◽  
Vol 496 (3) ◽  
pp. 3381-3389 ◽  
Author(s):  
Z Randriamanakoto ◽  
C H Ishwara-Chandra ◽  
A R Taylor
Keyword(s):  
Radio Emission ◽  
Active Galactic Nucleus ◽  
Energy Supply ◽  
Radio Galaxy ◽  
Angular Resolution ◽  
Radio Spectrum ◽  
Morphological Properties ◽  
Archival Data ◽  
Spectral Indices ◽  
Low Frequencies

ABSTRACT We report the discovery of a remnant radio active galactic nucleus (AGN) J1615+5452 in the field of ELAIS-N1. GMRT continuum observations at 150, 325, and 610 MHz combined with archival data from the 1.4 GHz NVSS survey were used to derive the radio spectrum of the source. At a redshift z ∼ 0.33, J1615+5452 has a linear size of ∼100 kpc and spectral indices ranging between $\alpha ^{1400}_{610} \lt -1.5$ and $\alpha ^{325}_{150} = -0.61 \pm 0.12$. While the source has a diffuse radio emission at low frequencies, we do not find evidence of core, jets, or hotspots in the 1.4 GHz VLA data of ∼5 arcsec angular resolution. Such morphological properties coupled with a curved radio spectrum suggest that the AGN fueling mechanisms undergo a shortage of energy supply which is typical of a dying radio AGN. This is consistent with the observed steep curvature in the spectrum Δα ≈ −1, the estimated synchrotron age of $t_{\rm s}=76.0\, ^{+7.4}_{-8.7}$ Myr and a toff/ts ratio of ∼0.3.

scholarly journals Some new observations relating to galactic radio sources and background structure

1964 ◽  
Vol 20 ◽  
pp. 107-114 ◽  
Author(s):  
E. R. Hill
Keyword(s):  
Radio Emission ◽  
Radio Telescope ◽  
Milky Way ◽  
Angular Resolution ◽  
Spectral Information ◽  
Radio Sources ◽  
Background Structure ◽  
The Galaxy ◽  
Galactic Radio

A survey of the distribution of radio emission at wavelengths of 75 and 20 cm along an extensive section of the Southern Milky Way has recently been carried out by M. Komesaroff and myself using the 210-foot radio telescope at Parkes. The area surveyed ranges from lII = 280 to 355° and extends on the average to 6 degrees either side of the plane. The beamwidths of the aerial at 75 and 20 cm are 50 and 14 min arc respectively. Observations at the shorter wavelength offer a picture of this section of the Galaxy at considerably higher angular resolution than hitherto available, while the 75-cm observations are expected to make a useful contribution to our spectral information.

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