The VSOP 5 GHz Active Galactic Nucleus Survey. IV. The Angular Size/Brightness Temperature Distribution

2004 ◽  
Vol 616 (1) ◽  
pp. 110-122 ◽  
Author(s):  
S. Horiuchi ◽  
E. B. Fomalont ◽  
W. K. Scott, A. R. Taylor ◽  
J. E. J. Lovell ◽  
G. A. Moellenbrock ◽  
...  
Keyword(s):  
Temperature Distribution ◽  
Brightness Temperature ◽  
Active Galactic Nucleus ◽  
Angular Size ◽  
5 Ghz

Snapshot Imaging with the Australia Telescope Compact Array

1995 ◽  
Vol 12 (2) ◽  
pp. 227-238 ◽  
Author(s):  
A. M. Burgess ◽  
R. W. Hunstead
Keyword(s):  
Dynamic Range ◽  
Angular Size ◽  
Integration Time ◽  
More Care ◽  
Snapshot Imaging ◽  
The One ◽  
5 Ghz ◽  
Total Integration ◽  
Deconvolution Techniques ◽  
Compact Array

AbstractRadio snapshot imaging is an efficient observing method which allows several sources to be observed in the one session. Snapshot observing with the Australia Telescope Compact Array (ATCA) involves special difficulties, as the small number of antennas combined with the short total integration time leads to high sidelobe levels in the raw images. The images can be improved markedly by standard deconvolution techniques, but more care is required in their use because of the difficulty in distinguishing real emission from artefacts. This study, based on a set of snapshot observations of strong sources at 5 GHz, gives guidance on both the planning of observations and the data reduction. We show that snapshot imaging with the 6 km ATCA can achieve a dynamic range of 100–200:1 provided certain conditions are met, namely a peak flux density > 100 mJy, an angular size ≤ 30″ and an hour-angle coverage spanning at least six well-separated 5-minute cuts. When observing weak sources it is essential for calibration sources to be selected carefully and observed frequently.

Radio continuum of galaxies with H2O megamaser disks

2017 ◽  
Vol 13 (S336) ◽  
pp. 139-140
Author(s):  
F. Kamali ◽  
C. Henkel ◽  
A. Brunthaler ◽  
C. M. V. Impellizzeri ◽  
K. M. Menten ◽  
...  
Keyword(s):  
Black Hole ◽  
Accretion Disk ◽  
Active Galactic Nucleus ◽  
Position Angle ◽  
Radio Continuum ◽  
Supermassive Black Hole ◽  
5 Ghz

AbstractIn our attempt to investigate the basic active galactic nucleus (AGN) paradigm requiring a centrally located supermassive black hole (SMBH), a close to Keplerian accretion disk and a jet perpendicular to its plane, we have searched for radio continuum in galaxies with H2O megamasers in their disks. We observed 18 such galaxies with the Very Large Baseline Array in C band (5 GHz, ~2 mas resolution) and we detected 5 galaxies at 8 σ or higher levels. For those sources for which the maser data is available, the positions of masers and those of the 5 GHz radio continuum sources coincide within the uncertainties, and the radio continuum is perpendicular to the maser disk’s orientation within the position angle uncertainties.

The VSOP 5 GHz Active Galactic Nucleus Survey. III. Imaging Results for the First 102 Sources

2004 ◽  
Vol 155 (1) ◽  
pp. 33-72 ◽  
Author(s):  
W. K. Scott ◽  
E. B. Fomalont ◽  
S. Horiuchi ◽  
J. E. J. Lovell ◽  
G. A. Moellenbrock ◽  
...  
Keyword(s):  
Active Galactic Nucleus ◽  
Imaging Results ◽  
5 Ghz

scholarly journals A Catalogue of 5 GHz Galactic Plane Sources

1979 ◽  
Vol 32 (4) ◽  
pp. 415
Author(s):  
RF Haynes ◽  
JL Caswell ◽  
LWJ Simons
Keyword(s):  
Point Source ◽  
Brightness Temperature ◽  
Galactic Plane ◽  
5 Ghz

A catalogue at 5 GHz of 915 sources in the galactic plane is presented. Sources with a peak beam brightness temperature of at least 0�2 K above the surrounding background are included, except in confused regions; a point source of 0�2 K corresponds to o� 26 Jy.

scholarly journals Measuring Cosmological Parameters with Very Long Baseline Interferometry

1999 ◽  
Vol 183 ◽  
pp. 67-67 ◽  
Author(s):  
L.I. Gurvits ◽  
K.I. Kellermann ◽  
S. Frey
Keyword(s):  
Cosmological Model ◽  
Very Long Baseline Interferometry ◽  
Cosmological Parameters ◽  
Angular Size ◽  
Linear Size ◽  
Radio Sources ◽  
Selection Effects ◽  
Extended Source ◽  
Long Baseline ◽  
5 Ghz

Very Long Baseline Interferometry (VLBI) allows us to study a core of AGN with a sub-parsec resolution. We analyze the dependencies “apparent angular size – redshift” and “apparent motion – redshift” which contain an imprint of the source's properties and cosmology. We present data on the “angular size – redshift” relation obtained with VLBI at 5 GHz on a sample of 300 AGN distributed over the widest available range of redshifts 0.016 ≤ z ≤ 4.5. The sample exceeds those used in similar studies earlier by Kellermann (1993, 79 sources) and Wilkinson et al. (1997, 160 sources). Unlike extended source, the angular size-redshift for compact radio sources appears consistent with the predictions of standard Friedmann world models with qo ≃ 0.5 without taking into account evolutionary effects or selection effects due to a “linear size – luminosity” or “linear size – spectral index” dependences. We discuss different approaches allowing us to disentangle intrinsic evolutionary properties of sources and parameters of the cosmological model. Recent estimates of parameters of the cosmological model are given. We also discuss a perspective of conclusive cosmological tests using the VLBI technique.

scholarly journals DETECTION OF A HIGH BRIGHTNESS TEMPERATURE RADIO CORE IN THE ACTIVE-GALACTIC-NUCLEUS-DRIVEN MOLECULAR OUTFLOW CANDIDATE NGC 1266

2013 ◽  
Vol 779 (2) ◽  
pp. 173 ◽  
Author(s):  
Kristina Nyland ◽  
Katherine Alatalo ◽  
J. M. Wrobel ◽  
Lisa M. Young ◽  
Raffaella Morganti ◽  
...  
Keyword(s):  
Brightness Temperature ◽  
Active Galactic Nucleus ◽  
High Brightness ◽  
Molecular Outflow

scholarly journals A full treatment of peculiar velocities on the reionization light cone

2019 ◽  
Vol 490 (1) ◽  
pp. 1255-1269 ◽  
Author(s):  
Emma Chapman ◽  
Mario G Santos
Keyword(s):  
Temperature Distribution ◽  
Brightness Temperature ◽  
Light Cone ◽  
Cosmological Parameters ◽  
Line Of Sight ◽  
Physical Parameters ◽  
Hydrogen Atoms ◽  
Peculiar Velocities ◽  
Full Treatment ◽  
Full Calculation

ABSTRACT Accurate simulations of the 21-cm signal from the Epoch of Reionization require the generation of maps at specific frequencies given the values of astrophysical and cosmological parameters. The peculiar velocities of the hydrogen atoms producing the 21-cm radiation result in a shift in the observed frequency of the 21-cm radiation and changes the amplitude of the signal itself. This is not an effect we can remove but instead needs to be accurately modelled to ensure we infer the correct physical parameters from an observation. We describe the full calculation of the distortion of the 21-cm signal, and propose a new code that integrates the 21-cm intensity along the line of sight for each individual light cone pixel to fully capture the intensity contributions from multiple redshifts. This algorithm naturally deals with the typical divergences found in standard approaches, allowing for large optical depths and 21-cm absorption events at high redshifts. We find the new method results in up to a 60 per cent decrease in power on the largest scales on the sky, and an increase of over 80 per cent on the smallest scales on the sky. We find that the new implementation of the light cone results in a longer tail of bright temperatures in the brightness temperature distribution, as a result of the successful circumventing of a previous cap that had to be implemented to avoid a divergence in the brightness temperature. We conclude that this full treatment of the evolution of the light cone pixel can be an important effect.

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