Continuum Radio Emission and Galactic Structure

1974 ◽  
Vol 60 ◽  
pp. 637-648 ◽  
Author(s):  
R. M. Price
Keyword(s):  
Radio Emission ◽  
Large Scale ◽  
Spiral Galaxies ◽  
Galactic Plane ◽  
Significant Proportion ◽  
Total Power ◽  
Average Volume ◽  
Spherical Component ◽  
Continuum Radio ◽  
Total Power Output

Recent studies of high latitude brightness have shown that in several regions a significant proportion of it is due to loop features. The largest of these are now thought to be local (within a few hundred parsecs) and perhaps to be due to supernova events.Aperture synthesis maps of 45 external spiral galaxies have shown large-scale continuum nonthermal features in the disks of some and, in general, an absence of spherical halos around the galaxies. This supports the view that the radio emission from our Galaxy can best be described as coming from a thick disk. Any large-scale spherical component could not have a volume emissivity greater than 1.5% of the average volume emissivity of the disk at meter wavelengths.A comparison of the disk radiation with new disk models suggests that the galactic plane radiation has two components: a base disk and a spiral component. Each of these contributes ~50% of the total power output of the disk at 150 MHz.

scholarly journals 41. The spherical component of the galactic radio emission

1957 ◽  
Vol 4 ◽  
pp. 233-237
Author(s):  
J. E. Baldwin
Keyword(s):  
Radio Emission ◽  
Brightness Temperature ◽  
Radio Telescope ◽  
Galactic Plane ◽  
Wave Length ◽  
Spherical Component ◽  
Long Wave ◽  
Half Power ◽  
Right Ascension ◽  
Galactic Radio

As part of the programme of observations with the large Cambridge radio telescope, a survey of the integrated radio emission has been made using one of the four elements of the interferometer. At a wave-length of 3·7 metres this aerial has beam-widths to half-power points of 2° in right ascension and 15° in declination. The use of a long wave-length makes it possible to obtain accurate measurements of the brightness temperature of the sky in regions away from the galactic plane. It is with the radiation from these regions that this paper is primarily concerned.

scholarly journals Large-Scale Galactic and Intergalactic Magnetic Fields

1990 ◽  
Vol 140 ◽  
pp. 90-94
Author(s):  
M. Fujimoto ◽  
T. Sawa
Keyword(s):  
Magnetic Fields ◽  
Radio Emission ◽  
Faraday Rotation ◽  
Large Scale ◽  
Spiral Galaxies ◽  
Radio Galaxies ◽  
Density Waves ◽  
Dynamo Theory ◽  
Spiral Density Waves

Large-scale axisymmetric and bisymmetric spiral (ASS and BSS) structures are found of magnetic fields in spiral galaxies by measuring the Faraday rotation of polarized radio emission. Dynamo theory is introduced to explain the field structures, and strong magnetogravitational interaction is suggested to occur between the BSS magnetic fields and spiral density waves. Up-to-date data about the rotation measures RM and redshifts z of QSOs and distant radio galaxies are given for discussing large-scale intergalactic magnetic fields.

scholarly journals Large Scale Magnetohydrodynamical Considerations in Spiral Galaxies

1983 ◽  
Vol 100 ◽  
pp. 157-158
Author(s):  
E. Battaner ◽  
M. L. Sánchez-Saavedra
Keyword(s):  
Magnetic Field ◽  
Steady State ◽  
Velocity Field ◽  
Large Scale ◽  
Spiral Galaxies ◽  
Galactic Center ◽  
Galactic Plane ◽  
Interstellar Gas ◽  
Plasma Distribution ◽  
Ring Structures

A magnetohydrodynamical result is deduced, which could contribute to our understanding of spiral and ring structures in galaxies. The usual expressions for the continuity, momentum and induction equations are adopted for the gas of a galaxy, and the following simplifying hypotesis are made : a) Steady state conditions, b) Axisymmetry, c) A velocity field given by (π=0, θ=θ(r), Z=0) for the interstellar gas (where π,θ and Z are the radial, azimuthal and vertical to the galactic plane components and r is the distance from the galactic center). Then, the direction of magnetic field must be azimuthal and the plasma distribution is compatible with ring structures.

Deep Survey of the Radio Continuum Emission along the Southern Galactic Plane at 2·4 GHz

1995 ◽  
Vol 12 (1) ◽  
pp. 54-59 ◽  
Author(s):  
A. R. Duncan ◽  
R. T. Stewart ◽  
R. F. Haynes ◽  
K. L. Jones
Keyword(s):  
Large Scale ◽  
Galactic Plane ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Total Power ◽  
Latitude Range ◽  
Power Maps ◽  
Deep Survey ◽  
5 Ghz ◽  
Linear Polarisation

AbstractWe have just completed the observational stage of a 2·4 GHz survey of the Southern Galactic Plane, using the Parkes radiotelescope, between 238° ≤ l ≤ 365° and with a latitude range of at least |b| ≤ 5° (beamwidth ~9 arcmin). The survey details both continuum emission and linear polarisation down to rms noises of approximately 12 and 4 mJy/beam respectively. It is the most sensitive survey to date of the southern plane at this frequency and should nicely complement the Effelsberg northern plane surveys in addition to the recent southern surveys such as the 843 MHz MOST survey and the 5 GHz PMN survey. The total-power maps are now completed, and reduction of the polarisation data is still in progress. In addition to compact HII regions and extragalactic sources, we are detecting on our total-power images a considerable amount of large-scale structure, and a significant number of new SNR candidates and spur-like features.

scholarly journals The Large Scale Distribution of Radio Continuum in E and SO Galaxies

1978 ◽  
Vol 77 ◽  
pp. 49-55
Author(s):  
R.D. Ekers
Keyword(s):  
Radio Emission ◽  
Radio Source ◽  
Large Scale ◽  
Spiral Galaxies ◽  
Elliptical Galaxy ◽  
Elliptical Galaxies ◽  
The Other ◽  
Radio Continuum ◽  
Radio Structure ◽  
Similar Morphology

If we look at the radio properties of the nearby ellipticals we find a situation considerably different from that just described by van der Kruit for the spiral galaxies. For example NGC 5128 (Cen A), the nearest giant elliptical galaxy, is a thousand times more powerful a radio source than the brightest spiral galaxies and furthermore its radio emission comes from a multiple lobed radio structure which bears no resemblance to the optical light distribution (e.g. Ekers, 1975). The other radio emitting elliptical galaxies in our neighbourhood, NGC 1316 (Fornax A), IC 4296 (1333–33), have similar morphology. A question which then arises is whether at lower levels we can detect radio emission coming from the optical image of the elliptical galaxies and which may be more closely related to the kind of emission seen in the spiral galaxies.

scholarly journals 50 YEARS OF RESEARCH IN CONTINUUM AT THE UTR-2 RADIO TELESCOPE

2021 ◽  
Vol 26 (4) ◽  
pp. 287-313
Author(s):  
M. A. Sidorchuk ◽  
◽  
N. M. Vasilenko ◽  
O. M. Ulyanov ◽  
O. O. Konovalenko ◽  
...  
Keyword(s):  
Radio Emission ◽  
Radio Telescope ◽  
Supernova Remnants ◽  
Large Scale ◽  
Low Frequencies ◽  
Decameter Wavelength ◽  
Galactic Clusters ◽  
The Galaxy ◽  
Continuum Radio ◽  
First Time

Purpose: The results of research in continuum decameter-wave radio emission of the Galaxy background, ionized hydrogen regions, supernova remnants, extragalactic discrete sources, extended galaxies, galactic clusters, extragalactic background are given. The aim of this work is reviewing the results achieved for over 50-years of the UTR-2 radiotelescope research of our Galaxy and its population, as well as extragalactic radio sources in the continuum radio emission spectrum at extremely low frequencies for the ground based observations. Design/methodology/approach: The review, analysis, collection of archival data in various publications related to the subjectof this work. Findings: The basic results of studying the ionized hydrogen regions, supernova remnants, Galaxy background emission and its large-scale structure are given, and the maps of these sources are obtained. The catalog of extragalactic discrete radio sources of the most Northern sky part and the cosmological conclusions based on its analysis are described; the estimate of the isotropic extragalactic background brightness temperature is obtained; for the first time, the observational results for the Andromeda galaxy and two galactic clusters Coma and A2255 are given briefly. Conclusions: All the results presented here emphasize the uniqueness and importance of research in the decameter wavelength range, and the large area, flexibility of structure, continuous improvement make the UTR-2 radio telescope an indispensable tool for solving the most important tasks of modern radio astronomy, despite its respectable age. For example, only in the range of 10 to 30 MHz the ionized part of the most common element in the universe, the hydrogen, becomes optically thick and begins to absorb the synchrotron emission on the line of sight, which allows rather easy separation of thermal and non-thermal components of radioemission. This property allows to determine the ionized hydrogen regions’ electron temperature and the electron concentration on the line of sight independently in studying the hydrogen emission regions. When studying the supernova remnants, we can determine the ionized matter location by their spectrum drops ‒ before, inside or behind the remnant. Based on the HB3 supernova remnant radio imagies, an assumption was made on the existence of an ionized hydrogen relic shell aroundit, being caused by the initial ultraviolet flash of a supernova. For the first time, the maps of the Northern sky large-scale structure in the declination range from ‒15° to +85° at extremely low frequencies 10, 12.6, 14.7, 16.7, 20 and 25 MHz for the ground-based observations are published, which, besides their own scientific value, may allow to correct the UTR-2 radio telescope imaging results. Using the full-resolution UTR-2 maps and the developed method of multifrequency T‒T diagrams, it was possible to separate the background radiation into galactic and extragalactic components and construct the spectrum of the latter. From the analysis of the most complete decameter wavelength range catalog of discrete sources, it follows that there is a gap in the redshift spatial distribution for all classes of extragalactic sources. The existence of an ionized hydrogen ring in the Andromeda Nebula disk has been suggested. It is shown that the main partof the galaxy clusters decameter-wave emission comes from haloes and relics. Key words: decameter range; discrete sources; supernovaremnants; catalog; continuum radio emission; HII regions; UTR-2; background emission

scholarly journals Multi-Country Scale Assessment of Available Energy Recovery Potential Using Micro-Hydropower in Drinking, Pressurised Irrigation and Wastewater Networks, Covering Part of the EU

Water ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 899
Author(s):  
Djordje Mitrovic ◽  
Miguel Crespo Chacón ◽  
Aida Mérida García ◽  
Jorge García Morillo ◽  
Juan Antonio Rodríguez Diaz ◽  
...  
Keyword(s):  
Drinking Water ◽  
Northern Ireland ◽  
Energy Recovery ◽  
Large Scale ◽  
Significant Proportion ◽  
Value Added ◽  
Cost Effective ◽  
Net Energy ◽  
Water Networks ◽  
Scale Assessment

Studies have shown micro-hydropower (MHP) opportunities for energy recovery and CO2 reductions in the water sector. This paper conducts a large-scale assessment of this potential using a dataset amassed across six EU countries (Ireland, Northern Ireland, Scotland, Wales, Spain, and Portugal) for the drinking water, irrigation, and wastewater sectors. Extrapolating the collected data, the total annual MHP potential was estimated between 482.3 and 821.6 GWh, depending on the assumptions, divided among Ireland (15.5–32.2 GWh), Scotland (17.8–139.7 GWh), Northern Ireland (5.9–8.2 GWh), Wales (10.2–8.1 GWh), Spain (375.3–539.9 GWh), and Portugal (57.6–93.5 GWh) and distributed across the drinking water (43–67%), irrigation (51–30%), and wastewater (6–3%) sectors. The findings demonstrated reductions in energy consumption in water networks between 1.7 and 13.0%. Forty-five percent of the energy estimated from the analysed sites was associated with just 3% of their number, having a power output capacity >15 kW. This demonstrated that a significant proportion of energy could be exploited at a small number of sites, with a valuable contribution to net energy efficiency gains and CO2 emission reductions. This also demonstrates cost-effective, value-added, multi-country benefits to policy makers, establishing the case to incentivise MHP in water networks to help achieve the desired CO2 emissions reductions targets.

scholarly journals GASTON: Galactic Star Formation with NIKA2. Evidence for the mass growth of star-forming clumps

2021 ◽  
Author(s):  
A J Rigby ◽  
N Peretto ◽  
R Adam ◽  
P Ade ◽  
M Anderson ◽  
...  
Keyword(s):  
Star Formation ◽  
Large Scale ◽  
Galactic Plane ◽  
High Sensitivity ◽  
High Mass ◽  
Evolutionary Stage ◽  
Mass Star ◽  
Mass Growth ◽  
Star Forming ◽  
Compact Source

Abstract Determining the mechanism by which high-mass stars are formed is essential for our understanding of the energy budget and chemical evolution of galaxies. By using the New IRAM KIDs Array 2 (NIKA2) camera on the Institut de Radio Astronomie Millimétrique (IRAM) 30-m telescope, we have conducted high-sensitivity and large-scale mapping of a fraction of the Galactic plane in order to search for signatures of the transition between the high- and low-mass star-forming modes. Here, we present the first results from the Galactic Star Formation with NIKA2 (GASTON) project, a Large Programme at the IRAM 30-m telescope which is mapping ≈2 deg2 of the inner Galactic plane (GP), centred on ℓ = 23${_{.}^{\circ}}$9, b = 0${_{.}^{\circ}}$05, as well as targets in Taurus and Ophiuchus in 1.15 and 2.00 mm continuum wavebands. In this paper we present the first of the GASTON GP data taken, and present initial science results. We conduct an extraction of structures from the 1.15 mm maps using a dendrogram analysis and, by comparison to the compact source catalogues from Herschel survey data, we identify a population of 321 previously-undetected clumps. Approximately 80 per cent of these new clumps are 70 μm-quiet, and may be considered as starless candidates. We find that this new population of clumps are less massive and cooler, on average, than clumps that have already been identified. Further, by classifying the full sample of clumps based upon their infrared-bright fraction – an indicator of evolutionary stage – we find evidence for clump mass growth, supporting models of clump-fed high-mass star formation.

scholarly journals Galaxy spin direction distribution in HST and SDSS show similar large-scale asymmetry

2020 ◽  
Vol 37 ◽  
Author(s):  
Lior Shamir
Keyword(s):  
Large Scale ◽  
Spiral Galaxies ◽  
Hubble Space Telescope ◽  
Gravitational Interaction ◽  
Large Data ◽  
Sloan Digital Sky Survey ◽  
Data Sets ◽  
Dipole Axis ◽  
Data Set ◽  
The Asymmetry

Abstract Several recent observations using large data sets of galaxies showed non-random distribution of the spin directions of spiral galaxies, even when the galaxies are too far from each other to have gravitational interaction. Here, a data set of $\sim8.7\cdot10^3$ spiral galaxies imaged by Hubble Space Telescope (HST) is used to test and profile a possible asymmetry between galaxy spin directions. The asymmetry between galaxies with opposite spin directions is compared to the asymmetry of galaxies from the Sloan Digital Sky Survey. The two data sets contain different galaxies at different redshift ranges, and each data set was annotated using a different annotation method. The results show that both data sets show a similar asymmetry in the COSMOS field, which is covered by both telescopes. Fitting the asymmetry of the galaxies to cosine dependence shows a dipole axis with probabilities of $\sim2.8\sigma$ and $\sim7.38\sigma$ in HST and SDSS, respectively. The most likely dipole axis identified in the HST galaxies is at $(\alpha=78^{\rm o},\delta=47^{\rm o})$ and is well within the $1\sigma$ error range compared to the location of the most likely dipole axis in the SDSS galaxies with $z>0.15$ , identified at $(\alpha=71^{\rm o},\delta=61^{\rm o})$ .

scholarly journals EyeHealer: A large-scale anterior eye segment dataset with eye structure and lesion annotations

2021 ◽  
Author(s):  
Wenjia Cai ◽  
Jie Xu ◽  
Ke Wang ◽  
Xiaohong Liu ◽  
Wenqin Xu ◽  
...  
Keyword(s):  
Deep Learning ◽  
Large Scale ◽  
Image Annotation ◽  
Clinical Care ◽  
Significant Proportion ◽  
Anterior Segment ◽  
Future Research ◽  
Learning Models ◽  
Anterior Eye Segment ◽  
Segmentation Models

Abstract Anterior segment eye diseases account for a significant proportion of presentations to eye clinics worldwide, including diseases associated with corneal pathologies, anterior chamber abnormalities (e.g. blood or inflammation) and lens diseases. The construction of an automatic tool for the segmentation of anterior segment eye lesions will greatly improve the efficiency of clinical care. With research on artificial intelligence progressing in recent years, deep learning models have shown their superiority in image classification and segmentation. The training and evaluation of deep learning models should be based on a large amount of data annotated with expertise, however, such data are relatively scarce in the domain of medicine. Herein, the authors developed a new medical image annotation system, called EyeHealer. It is a large-scale anterior eye segment dataset with both eye structures and lesions annotated at the pixel level. Comprehensive experiments were conducted to verify its performance in disease classification and eye lesion segmentation. The results showed that semantic segmentation models outperformed medical segmentation models. This paper describes the establishment of the system for automated classification and segmentation tasks. The dataset will be made publicly available to encourage future research in this area.

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