scholarly journals An Interpretation of the Distribution of Metre Wavelength Radio Emission

1968 ◽  
Vol 21 (2) ◽  
pp. 167 ◽  
Author(s):  
KW Yates
Keyword(s):  
High Latitude ◽  
Large Scale ◽  
Galactic Halo ◽  
Galactic Plane ◽  
Absolute Calibration ◽  
Fundamental Difficulty ◽  
The Galaxy ◽  
Calibration Accuracy ◽  
Limit Estimate ◽  
Spiral Arm

A recent 85 MHz survey of the southern sky had an absolute calibration accuracy and resolution comparable with a number of surveys made for the northern skies. By combining the results of these surveys in both hemispheres a complete sky map has been produced, and in this paper an analysis is made of the distribution of the medium and high latitude emission. A fundamental difficulty encountered is the identification and isolation of the spurs of emission projecting from the galactic plane. Two hypotheses are proposed. The first attributes the spurs to a large-scale feature associated with the galactic core and the remaining emission to a galactic halo. The second postulates the origin of the spurs within the local spiral arm, which is itself considered to contribute significantly to the high latitude background. An upper-limit estimate of the emissivity of the local arm is made from currently available independent data. Using this result a model local arm is proposed, which, together with an isotropic component from beyond the Galaxy and a small additional galactic component, explains the observed distribution.

scholarly journals Radio Studies of Cosmic Rays in the Galaxy

1991 ◽  
Vol 144 ◽  
pp. 187-196
Author(s):  
W. Reich
Keyword(s):  
Supernova Remnants ◽  
Large Scale ◽  
Galactic Halo ◽  
Galactic Plane ◽  
Thermal Emission ◽  
Galactic Disk ◽  
Cosmic Ray ◽  
Radio Continuum ◽  
The Galaxy ◽  
Radio Studies

Changes of the cosmic ray electron spectrum throughout the Galaxy have been found, based on the comparison of large-scale radio continuum surveys. These observations are not compatible with the assumption of a static Galactic halo, but indicate the existence of a Galactic wind. Galactic plane surveys reveal sources of cosmic ray electrons in the Galactic disk. Recent studies of the population of radio sources show no evidence for a large number of compact Galactic non-thermal sources. Most of the extended sources are probably HII-regions. Relatively few new supernova remnants (SNRs) with low surface brightness could be identified. Most of the non-thermal emission in the disk-halo interface seems diffuse or unresolved, even at arcmin angular resolution.

scholarly journals The magnetic structure of our Galaxy: a review of observations

2008 ◽  
Vol 4 (S259) ◽  
pp. 455-466 ◽  
Author(s):  
JinLin Han
Keyword(s):  
Magnetic Fields ◽  
Magnetic Structure ◽  
Large Scale ◽  
Galactic Halo ◽  
Galactic Center ◽  
Galactic Plane ◽  
Galactic Disk ◽  
Dust Emission ◽  
Measure Data ◽  
Radio Sources

AbstractThe magnetic structure in the Galactic disk, the Galactic center and the Galactic halo can be delineated more clearly than ever before. In the Galactic disk, the magnetic structure has been revealed by starlight polarization within 2 or 3 kpc of the Solar vicinity, by the distribution of the Zeeman splitting of OH masers in two or three nearby spiral arms, and by pulsar dispersion measures and rotation measures in nearly half of the disk. The polarized thermal dust emission of clouds at infrared, mm and submm wavelengths and the diffuse synchrotron emission are also related to the large-scale magnetic field in the disk. The rotation measures of extragalactic radio sources at low Galactic latitudes can be modeled by electron distributions and large-scale magnetic fields. The statistical properties of the magnetized interstellar medium at various scales have been studied using rotation measure data and polarization data. In the Galactic center, the non-thermal filaments indicate poloidal fields. There is no consensus on the field strength, maybe mG, maybe tens of μG. The polarized dust emission and much enhanced rotation measures of background radio sources are probably related to toroidal fields. In the Galactic halo, the antisymmetric RM sky reveals large-scale toroidal fields with reversed directions above and below the Galactic plane. Magnetic fields from all parts of our Galaxy are connected to form a global field structure. More observations are needed to explore the untouched regions and delineate how fields in different parts are connected.

scholarly journals Measuring and calibrating galactic synchrotron emission

2008 ◽  
Vol 4 (S259) ◽  
pp. 603-612 ◽  
Author(s):  
Wolfgang Reich ◽  
Patricia Reich
Keyword(s):  
Large Scale ◽  
Angular Resolution ◽  
Galactic Plane ◽  
Synchrotron Emission ◽  
Diffuse Emission ◽  
Sky Surveys ◽  
Zero Level ◽  
The Galaxy ◽  
Scale Properties ◽  
Relative Measurements

AbstractOur position inside the Galaxy requires all-sky surveys to reveal its large-scale properties. The zero-level calibration of all-sky surveys differs from standard ‘relative’ measurements, where a source is measured in respect to its surroundings. All-sky surveys aim to include emission structures of all angular scales exceeding their angular resolution including isotropic emission components. Synchrotron radiation is the dominating emission process in the Galaxy up to frequencies of a few GHz, where numerous ground based surveys of the total intensity up to 1.4 GHz exist. Its polarization properties were just recently mapped for the entire sky at 1.4 GHz. All-sky total intensity and linear polarization maps from WMAP for frequencies of 23 GHz and higher became available and complement existing sky maps. Galactic plane surveys have higher angular resolution using large single-dish or synthesis telescopes. Polarized diffuse emission shows structures with no relation to total intensity emission resulting from Faraday rotation effects in the interstellar medium. The interpretation of these polarization structures critically depends on a correct setting of the absolute zero-level in Stokes U and Q.

scholarly journals On role of Triple Systems in the Dynamics of the Galaxy: Stars with High Velocities

1995 ◽  
Vol 164 ◽  
pp. 369-369
Author(s):  
J. Anosova ◽  
J. Colin ◽  
L. Kiseleva
Keyword(s):  
Galactic Halo ◽  
Galactic Plane ◽  
Stellar Systems ◽  
Galactic Disc ◽  
Triple Systems ◽  
The Galaxy ◽  
Escape Process ◽  
Very High

There are a number of stars with very high pecular velocities in the Galactic halo within the region of about 1.5 kpc from the Galactic plane. At least some of these stars could be the result of an escape process in multiple stellar systems located in the Galactic disc.

A discussion on infared astronomy - Expected infrared spectra of gaseous nebulae

1969 ◽  
Vol 264 (1150) ◽  
pp. 241-247 ◽  
Keyword(s):  
Infrared Spectra ◽  
Galactic Plane ◽  
Interstellar Extinction ◽  
Mount Everest ◽  
Gaseous Nebulae ◽  
The Galaxy ◽  
The Mean ◽  
Spiral Arm

If we are asked why we want to use the infrared to observe gaseous nebulae, we might reply with George Mallory, who was asked why he wanted to climb Mount Everest, ‘Because its there’. More specifically, one reason is the very great space penetration possible in the infrared. Diffuse nebulae characteristically are close to the galactic plane, and interstellar extinction therefore prevents the observation of distant objects. At MATHS FORMULA the mean range to which diffuse nebulae can easily be observed is about 1500 parsecs (pc), while many of these nebulae are so reddened as to be nearly unobservable at Hβ. It is for this reason that at present the observation of diffuse nebulae is almost entirely limited to our own spiral arm and its immediate neighbours. However, because of the decrease of interstellar extinction to longer wavelengths, at 1 μm the range of observation would be about 3000 pc; at 2 μm about 10 000 pc, comparable with the distance to the centre of the Galaxy; and at 10μm, about 100 000 pc, far larger than the diameter of the Galaxy. (The form of the interstellar reddening curve is from Whitford 1958.)

scholarly journals Giant Molecular Clouds in the Galaxy: The Massachusetts-Stony Brook CO Galactic Plane Survey

1987 ◽  
Vol 115 ◽  
pp. 499-499 ◽  
Author(s):  
P. M. Solomon
Keyword(s):  
Molecular Clouds ◽  
Galactic Plane ◽  
Far Infrared ◽  
Formation Mechanisms ◽  
H Ii Regions ◽  
Giant Molecular Clouds ◽  
Star Forming ◽  
The Galaxy ◽  
Two Populations ◽  
Spiral Arm

The CO Galactic Plane Survey consists of 40,572 spectral line observations in the region between 1 = 8° to 90° and b = −1°.05 to +1°.05 spaced every 3 arc minutes, carried out with the FCRAO 14-m antenna. The velocity coverage from −100 to +200 km/s includes emission from all galactic radii. This high resolution survey was designed to observe and identify essentially all molecular clouds or cloud components larger than 10 parsecs in the inner galaxy. There are two populations of molecular clouds which separate according to temperature. The warm clouds are closely associated with H II regions, exhibit a non-axisymmetric galactic distribution and are a spiral arm population. The cold clouds are a disk population, are not confined to any patterns in longitude-velocity space and must be widespread in the galaxy both in and out of spiral arms. The correlation between far infrared luminosities from IRAS, and molecular masses from CO is utilized to determine a luminosity to mass ratio for the clouds. A face-on picture of the galaxy locating the warm population is presented, showing ring like or spiral arm features at R ∼ 5, 7.5 and 9 kpc. The cloud size and mass spectrum will be discussed and evidence presented showing the presence of clusters of giant molecular clouds with masses of 106 to 107 M⊙. The two populations of clouds probably have different star forming luminosity functions. The implication of the two populations for star formation mechanisms will be discussed.

A CO Survey of the Southern Galactic Plane

1981 ◽  
Vol 4 (2) ◽  
pp. 243-247 ◽  
Author(s):  
W. H. McCutcheon ◽  
B. J. Robinson ◽  
J. B. Whiteoak
Keyword(s):  
Northern Hemisphere ◽  
Atomic Hydrogen ◽  
Molecular Hydrogen ◽  
Large Scale ◽  
Galactic Plane ◽  
Galactic Centre ◽  
Hydrogen Distribution ◽  
Millimetre Wave ◽  
The Galaxy ◽  
Wave Emission

Millimetre-wave emission from the CO molecule has proven to be an extremely useful probe of the cold, dense clouds of molecular hydrogen in the Galaxy. Previous studies of the large-scale distribution of CO in the galactic plane (Scoville and Solomon 1975; Burton et al. 1975; Bash and Peters 1976; Burton and Gordon 1978; Solomon et al. 1979b; Cohen et al. 1980) have all been of the northern hemisphere and primarily at longitudes 0° ≤ l ≥ 80°. These studies have revealed the striking characteristic that the CO, and by implication molecular hydrogen clouds, are concentrated in a ring extending from 4 to 8 kpc from the galactic centre. This is in sharp contrast to the atomic hydrogen distribution, which is fairly constant over the extended region from 4 to 13 kpc but correlates well with other Population I indicators.

scholarly journals Gamma-ray observations and the large scale structure of the galaxy

1979 ◽  
Vol 84 ◽  
pp. 125-130
Author(s):  
J. A. Paul
Keyword(s):  
Present Status ◽  
Large Scale ◽  
Gamma Ray ◽  
Galactic Plane ◽  
Large Scale Structure ◽  
Galactic Disc ◽  
Γ Radiation ◽  
Latitude Dependence ◽  
The Galaxy ◽  
Γ Ray

Within the last few years, γ-ray astronomy has shifted from the discovery phase to the exploratory phase, thanks to the SAS-2 and COS-B satellites. The strongest feature of the γ-ray sky is the overwhelming emission of the galactic disc; even the radiation observed away from the galactic plane appears to be predominantly galactic, on the basis of its latitude dependence (Fichtel et al., 1978). Nevertheless, extragalactic γ-ray astronomy is not hopeless: the γ-radiation of the nearby quasar 3C273 has been very recently detected (Swanenburg et al., 1978). A brief summary of the present status of the galactic γ-ray astronomy follows.

scholarly journals Distribution of CO in the Southern Milky Way and large-scale structure in the Galaxy

1985 ◽  
Vol 106 ◽  
pp. 203-204
Author(s):  
W.H. Mccutcheon ◽  
B. J. Robinson ◽  
R. N. Manchester ◽  
J. B. Whiteoak
Keyword(s):  
Large Scale ◽  
Milky Way ◽  
Galactic Plane ◽  
Large Scale Structure ◽  
Sampling Interval ◽  
Scale Structure ◽  
Plane Region ◽  
The Galaxy ◽  
Csiro Division

The southern galactic-plane region, in the ranges 294° ≤ 1 ≤ 358°, −0°.075 ≤ b ≤ 0°.075, has been surveyed in the J = 1–0 line of 12CO with a sampling interval of 3′ arc. Observations were made with the 4-metre telescope at the CSIRO Division of Radiophysics in 1980 and 1981. Details of equipment and observing procedure are given in Robinson et al. (1982, 1983); see also McCutcheon et al. (1983).

scholarly journals GLOSTAR: Radio Source Catalog I. 28° <  ℓ < 36° and |b| < 1°

2019 ◽  
Vol 627 ◽  
pp. A175 ◽  
Author(s):  
S.-N. X. Medina ◽  
J. S. Urquhart ◽  
S. A. Dzib ◽  
A. Brunthaler ◽  
B. Cotton ◽  
...  
Keyword(s):  
Star Formation ◽  
Software Package ◽  
Large Scale ◽  
Galactic Plane ◽  
Planetary Nebulae ◽  
Radio Continuum ◽  
Spectral Indices ◽  
The Galaxy ◽  
Reported Data ◽  
Cross Matching

Context. Radio continuum surveys of the Galactic plane are an excellent way to identify different source populations such as planetary nebulae, H II regions, and radio stars and characterize their statistical properties. The Global View of Star Formation in the Milky Way (GLOSTAR) survey will study the star formation in the Galactic plane between −2° < ℓ < 85° and |b| < 1° with unprecedented sensitivity in both flux density (∼40 μJy beam−1) and range ofangular scales (∼1".5 to the largest radio structures in the Galaxy). Aims. In this paper we present the first results obtained from a radio continuum map of a 16-square-degree-sized region of the Galactic plane centered on ℓ = 32° and b = 0° (28° < ℓ < 36° and |b| < 1°). This map has a resolution of 18″ and a sensitivity of ∼60−150 μJy beam−1. Methods. We present data acquired in 40 h of observations with the VLA in D-configuration. Two 1 GHz wide sub-bands were observed simultaneously and they were centered at 4.7 and 6.9 GHz. These data were calibrated and imaged using the Obit software package. The source extraction was performed using the BLOBCAT software package and verified through a combination of visual inspection and cross-matching with other radio and mid-infrared surveys. Results. The final catalog consists of 1575 discrete radio sources and 27 large scale structures (including W43 and W44). By cross-matching with other catalogs and calculating the spectral indices (S(ν) ∝ να), we have classified 231 continuum sources as H II regions, 37 as ionization fronts, and 46 as planetary nebulae. The longitude and latitude distribution and negative spectral indices are all consistent with the vast majority of the unclassified sources being extragalactic background sources. Conclusions. We present a catalog of 1575 radio continuum sources and discuss their physical properties, emission nature, and relation to previously reported data. These first GLOSTAR results have increased the number of reliable H II regions in this part of the Galaxy by a factor of four.

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