scholarly journals INTERSTELLAR MEDIUM AND DECAMETER RADIO SPECTROSCOPY

2021 ◽  
Vol 26 (4) ◽  
pp. 314-325
Author(s):  
S. V. Stepkin ◽  
◽  
O. O. Konovalenko ◽  
Y. V. Vasylkivskyi ◽  
D. V. Mukha ◽  
...  
Keyword(s):  
Interstellar Medium ◽  
Radio Telescope ◽  
Radio Astronomy ◽  
Low Frequency ◽  
Spectral Lines ◽  
Physical Parameters ◽  
Recombination Mechanism ◽  
Radio Recombination Lines ◽  
Radio Spectroscopy ◽  
Correlation Spectrum

Purpose: The analytical review of the main results of research in the new direction of the low-frequency radio astronomy, the interstellar medium radio spectroscopy at decameter waves, which had led to astrophysical discovery, recording of the radio recombination lines in absorption for highly excited states of interstellar carbon atoms (more than 600). Design/methodology/approach: The UTR-2 world-largest broadband radio telescope of decameter waves optimally connected with the digital correlation spectrum analyzers has been used. Continuous modernization of antenna system and devices allowed increasing the analysis band from 100 kHzto 24 MHz and a number of channels from 32 to 8192. The radio telescope and receiving equipment with appropriate software allowed to have a long efficient integration time enough for a large line series simultaneously with high resolution, noise immunity and relative sensitivity. Findings: A new type of interstellar spectral lines has been discovered and studied, the interstellar carbon radio recombination lines in absorption for the record high excited atoms with principal quantum numbers greater than 1000. The line parameters (intensity, shape, width, radial velocity) and their relation ship with the interstellar medium physical parameters have been determined. The temperature of line forming regions is about 100 K, the electron concentration up to 0.1 cm–3 and the size of a line forming region is about 10 pc. For the first time, radio recombination lines were observed in absorption. They have significant broadening and are amplified by the dielectronic-like recombination mechanism and are also the lowest frequency lines in atomic spectroscopy. Conclusions: The detected low-frequency carbon radio recombination lines and their observations have become a new highly effective tool for the cold partially ionized interstellar plasma diagnostics. Using them allows obtaining the information which is not available with the other astrophysical methods. For almost half a century of their research, a large amount of hardware-methodical and astrophysical results have been obtained including a record number of Galaxy objects, where there levant lines have been recorded. The domestic achievements have stimulated many theoretical and experimental studies in other countries, but the scientific achievements of Ukrainian scientists prove the best prospects for further development of this very important area of astronomical science. Key words: low-frequency radio astronomy; radio telescope; interstellar medium; radio recombination lines; carbon; hydrogen; spectral analyzer

scholarly journals Status of the Thai 40-m Radio Telescope

2017 ◽  
Vol 13 (S337) ◽  
pp. 346-347
Author(s):  
Phrudth Jaroenjittichai
Keyword(s):  
Radio Telescope ◽  
Radio Astronomy ◽  
Time Domain ◽  
Phased Array ◽  
Low Frequency ◽  
Great Leap ◽  
Great Leap Forward ◽  
Astronomical Research ◽  
L Band ◽  
K Band

AbstractSince the first light of the 2.4-m Thai National Telescope in 2013, Thailand foresees another great leap forward in astronomy. A project known as “Radio Astronomy Network and Geodesy for Development” (RANGD) by National Astronomical Research Institute of Thailand (NARIT) has been approved for year 2017-2021. A 40-m radio telescope has been planned to operate up to 115-GHz observation with prime-focus capability for low frequency and phased array feed receivers. The telescope’s first light is expected in late 2019 with a cryogenics K-band and L-band receivers. RFI environment at the site has been investigated and shown to be at reasonable level. A 13-m VGOS telescope is also included for geodetic applications. Early single-dish science will focus on time domain observations, such as pulsars and transients, outbursts and variability of maser and AGN sources.

scholarly journals Analysis and discussion of a sample of 25 gigahertz-peaked spectra pulsars

2017 ◽  
Vol 13 (S337) ◽  
pp. 352-353
Author(s):  
Jarosław Kijak ◽  
Wojciech Lewandowski ◽  
Karolina Rożko
Keyword(s):  
Interstellar Medium ◽  
Radio Telescope ◽  
Physical Parameters ◽  
Low Frequencies ◽  
Inverted Spectrum

AbstractWe identified gigahertz-peaked spectra behavior from our radio interferometric observations at low frequencies using the Giant Metrewave Radio Telescope. We modeled the turnover spectra based on thermal free-free absorption in the interstellar medium. The free-free absorption is believed to be responsible for the inverted spectrum. Using the model, we were able to put some observational constrains on the physical parameters of the absorbing matter, which allows us to distinguish between the possible sources of absorption.

scholarly journals A roadmap towards a space-based radio telescope for ultra-low frequency radio astronomy

2020 ◽  
Vol 65 (2) ◽  
pp. 856-867 ◽  
Author(s):  
M.J. Bentum ◽  
M.K. Verma ◽  
R.T. Rajan ◽  
A.J. Boonstra ◽  
C.J.M. Verhoeven ◽  
...  
Keyword(s):  
Radio Telescope ◽  
Radio Astronomy ◽  
Low Frequency

The Llanherne Low Frequency Radio Telescope

1972 ◽  
Vol 2 (3) ◽  
pp. 135-137 ◽  
Author(s):  
G. R. A. Ellis
Keyword(s):  
Lower Limit ◽  
Radio Telescope ◽  
Radio Astronomy ◽  
Angular Resolution ◽  
Low Frequency ◽  
Earth Satellite ◽  
The Sun ◽  
Frequency Range ◽  
Interstellar Absorption ◽  
The Galaxy

A large proportion of the easily accessible radio astronomy spectrum lies between 50 MHz and a lower limit of about 1 MHz set by interstellar absorption. The features of the spectrum in this frequency range, from sources such as the galaxy, extragalactic sources, pulsars, the Sun and Jupiter, remain only partially explored mainly owing to the large sizes of telescopes necessary to obtain adequate angular resolution and sensitivity. In addition, below 20 MHz, interference from man-made radiation and from the ionosphere severely hinders observations. At the lowest frequencies, the effects of the ionosphere can be overcome by using earth satellite telescopes at the expense of greatly increased difficulty in attaining sufficient telescope aperture.

scholarly journals Dissecting the molecular structure of the Orion B cloud: insight from principal component analysis

2017 ◽  
Vol 599 ◽  
pp. A100 ◽  
Author(s):  
Pierre Gratier ◽  
Emeric Bron ◽  
Maryvonne Gerin ◽  
Jérôme Pety ◽  
Viviana V. Guzman ◽  
...  
Keyword(s):  
Principal Component Analysis ◽  
Interstellar Medium ◽  
Principal Component ◽  
Component Analysis ◽  
Volume Density ◽  
Physical Structure ◽  
Spectral Lines ◽  
Large Field ◽  
Physical Parameters ◽  
Wide Field

Context. The combination of wideband receivers and spectrometers currently available in (sub-)millimeter observatories deliver wide-field hyperspectral imaging of the interstellar medium. Tens of spectral lines can be observed over degree wide fields in about 50 h. This wealth of data calls for restating the physical questions about the interstellar medium in statistical terms. Aims. We aim to gain information on the physical structure of the interstellar medium from a statistical analysis of many lines from different species over a large field of view, without requiring detailed radiative transfer or astrochemical modeling. Methods. We coupled a non-linear rescaling of the data with one of the simplest multivariate analysis methods, namely the principal component analysis, to decompose the observed signal into components that we interpret first qualitatively and then quantitatively based on our deep knowledge of the observed region and of the astrochemistry at play. Results. We identify three principal components, linear compositions of line brightness temperatures, that are correlated at various levels with the column density, the volume density and the UV radiation field. Conclusions. When sampling a sufficiently diverse mixture of physical parameters, it is possible to decompose the molecular emission in order to gain physical insight on the observed interstellar medium. This opens a new avenue for future studies of the interstellar medium.

scholarly journals Low-frequency Carbon Radio Recombination Lines. II. The Diffuse Interstellar Medium

2017 ◽  
Vol 837 (2) ◽  
pp. 142 ◽  
Author(s):  
F. Salgado ◽  
L. K. Morabito ◽  
J. B. R. Oonk ◽  
P. Salas ◽  
M. C. Toribio ◽  
...  
Keyword(s):  
Interstellar Medium ◽  
Low Frequency ◽  
Radio Recombination Lines

scholarly journals First Radio Astronomy Examination of the Low-Frequency Broadband Active Antenna Subarray

2014 ◽  
Vol 2014 ◽  
pp. 1-5 ◽  
Author(s):  
A. A. Stanislavsky ◽  
I. N. Bubnov ◽  
A. A. Konovalenko ◽  
A. A. Gridin ◽  
V. V. Shevchenko ◽  
...  
Keyword(s):  
Remote Control ◽  
Antenna Array ◽  
Radio Telescope ◽  
Personal Computer ◽  
Radio Astronomy ◽  
Low Frequency ◽  
Delay Lines ◽  
Online Interaction ◽  
Active Antenna ◽  
Parallel Data

We present the 25-element active antenna array and its remote control in the framework of the GURT project, the Ukrainian Radio Telescope of a new age. To implement beamforming, the array is phased with the help of discrete cable delay lines in analog manner. The remote control of the array is carried out through the paired encoder and decoder that can transmit parallel data about antenna codes serially. The microcontroller provides the online interaction between personal computer and beamformers with the help of the encoder-decoder system through wires or wireless. The antenna pattern has been measured by radio astronomy methods.

Low-frequency radio recombination lines: observations and data processing

2017 ◽  
Vol 23 (1) ◽  
pp. 50-53
Author(s):  
A.A. Konovalenko ◽  
◽  
S.V. Stepkin ◽  
E.V. Vasilkovskiy ◽  
◽  
...  
Keyword(s):  
Data Processing ◽  
Low Frequency ◽  
Radio Recombination Lines
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