scholarly journals Bright Prospects: Comparing the Hα Survey with Large-scale Radio Continuum Emission

1998 ◽  
Vol 15 (1) ◽  
pp. 50-55
Author(s):  
A. R. Duncan ◽  
R. F. Haynes
Keyword(s):  
Supernova Remnants ◽  
Large Scale ◽  
Galactic Plane ◽  
Thermal Emission ◽  
High Sensitivity ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Low Density ◽  
Polar Plumes ◽  
Spiral Arm

AbstractProspects for comparisons between the AAO/UKST Hα survey and large-scale radio continuum emission are considered, with particular reference to the recently completed Parkes 2·4 GHz survey of the southern Galactic Plane. Both these surveys have a high sensitivity to thermal emission, and comparisons between the Parkes work and previous Hα surveys show many objects in common. Possibilities for new detections include: a number of new supernova remnants; the faint extensions and envelopes surrounding ‘classical’ HII complexes, and other faint regions of thermal emission; several active HII complexes, including an outflow of ionised gas from IC 4628 and a number of bi-polar ‘plumes’ of low-density, thermal material apparently associated with HII complexes on the Carina spiral arm.

scholarly journals Radio continuum emission in the northern Galactic plane: Sources and spectral indices from the THOR survey

2018 ◽  
Vol 619 ◽  
pp. A124 ◽  
Author(s):  
Y. Wang ◽  
S. Bihr ◽  
M. Rugel ◽  
H. Beuther ◽  
K. G. Johnston ◽  
...  
Keyword(s):  
Supernova Remnants ◽  
Milky Way ◽  
Galactic Plane ◽  
High Redshift ◽  
High Sensitivity ◽  
Large Percentage ◽  
Radio Continuum ◽  
Continuum Emission ◽  
High Angular Resolution ◽  
Spectral Indices

Context Radio continuum surveys of the Galactic plane can find and characterize H II regions, supernova remnants (SNRs), planetary nebulae (PNe), and extragalactic sources. A number of surveys at high angular resolution (≤25″) at different wavelengths exist to study the interstellar medium (ISM), but no comparable high-resolution and high-sensitivity survey exists at long radio wavelengths around 21 cm. Aims. Our goal is to investigate the 21 cm radio continuum emission in the northern Galactic plane at < 25″ resolution. Methods We observed a large percentage of the Galactic plane in the first quadrant of the Milky Way (l = 14.0−67.4° and |b| ≤ 1.25°) with the Karl G. Jansky Very Large Array (VLA) in the C-configuration covering six continuum spectral windows (SPW). These data provide a detailed view on the compact as well as extended radio emission of our Galaxy and thousands of extragalactic background sources. Results We used the BLOBCAT software and extracted 10 916 sources. After removing spurious source detections caused by the side lobes of the synthesized beam, we classified 10 387 sources as reliable detections. We smoothed the images to a common resolution of 25″ and extracted the peak flux density of each source in each SPW to determine the spectral indices α (assuming I(ν) ∝ να). By cross-matching with catalogs of H II regions, SNRs, PNe, and pulsars, we found radio counterparts for 840 H II regions, 52 SNRs, 164 PNe, and 38 pulsars. We found 79 continuum sources that are associated with X-ray sources. We identified 699 ultra-steep spectral sources (α < −1.3) that could be high-redshift galaxies. About 9000 of the sources we extracted are not classified specifically, but based on their spatial and spectral distribution, a large percentage of these are likely to be extragalactic background sources. More than 7750 sources do not have counterparts in the SIMBAD database and more than 3760 sources do not have counterparts in the NED database. Conclusions Studying the long wavelengths centimeter continuum emission and the associated spectral indices allows us to characaterize a large percentage of Galactic and extragalactic radio sources in the area of the northern inner Milky Way. This database will be extremely useful for future studies of a diverse set of astrophysical objects.

scholarly journals The Large-Scale Distribution of Synchrotron Emissivity in the Galaxy

1981 ◽  
Vol 94 ◽  
pp. 223-224 ◽  
Author(s):  
S. Kearsey ◽  
J. L. Osborne ◽  
S. Phillipps ◽  
C.G.T. Haslam ◽  
C. J. Salter ◽  
...  
Keyword(s):  
Supernova Remnants ◽  
Large Scale ◽  
Galactic Plane ◽  
Thermal Emission ◽  
Radio Continuum ◽  
3 Dimensional ◽  
The Galaxy ◽  
Dimensional Distribution ◽  
Alternative Approaches ◽  
Best Fit

The all-sky radio continuum map at 408 MHz presented at this symposium by Haslam et al. can be interpreted in terms of the large-scale 3-dimensional distribution of synchrotron emissivity in the Galaxy when due allowance is made for the thermal emission. Its derivation from a 2-dimensional map must involve a number of assumptions so it is instructive to compare the results of alternative approaches (described in detail in forthcoming papers by the present authors). In both cases the variation of emissivity in the galactic plane is obtained from the observed intensity profile at b=0o and then the z-variation is chosen to give the best fit to the complete map. The observed profile is shown in the figure with and without the contributions of catalogued supernova remnants and HII regions.

scholarly journals A Sino-German λ6 cm polarisation survey of the Galactic plane

2019 ◽  
Vol 623 ◽  
pp. A105 ◽  
Author(s):  
X. Y. Gao ◽  
P. Reich ◽  
L. G. Hou ◽  
W. Reich ◽  
J. L. Han
Keyword(s):  
Survey Data ◽  
Supernova Remnants ◽  
Large Scale ◽  
Angular Resolution ◽  
Galactic Plane ◽  
Thermal Emission ◽  
Small Diameter ◽  
Radio Continuum ◽  
High Angular Resolution ◽  
Radio Sources

Context. Large-scale radio continuum surveys provide data to get insights into the physical properties of radio sources. H II regions are prominent radio sources produced by thermal emission of ionised gas around young massive stars. Aims. We identify and analyse H II regions in the Sino-German λ6 cm polarisation survey of the Galactic plane. Methods. Objects with flat radio continuum spectra together with infrared and/or Hα emission were identified as H II regions. For H II regions with small apparent sizes, we cross-matched the λ6 cm small-diameter source catalogue with the radio H II region catalogue compiled by Paladini and the infrared H II region catalogue based on the WISE data. Effelsberg λ21 cm and λ11 cm continuum survey data were used to determine source spectra. High angular resolution data from the Canadian Galactic Plane Survey and the NRAO VLA Sky Survey were used to solve the confusion when low angular resolution observations were not sufficient. Extended H II regions were identified by eye by overlaying the Paladini and the WISE H II regions onto the λ6 cm survey images for coincidences. The TT-plot method was employed for spectral index verification. Results. A total of 401 H II regions were identified and their flux densities were determined with the Sino-German λ6 cm survey data. In the surveyed area, 76 pairs of sources are found to be duplicated in the Paladini H II region catalogue, mainly due to the non-distinction of previous observations with different angular resolutions and 78 objects in their catalogue are misclassified as H II regions, being actually planetary nebulae, supernova remnants, or extragalactic sources that have steep spectra. More than 30 H II regions and H II region candidates from our λ6 cm survey data, especially extended ones, do not have counterparts in the WISE H II region catalogue, of which 9 are identified for the first time. Our results imply that some more Galactic H II regions still await to be discovered and the combination of multi-domain observations is important for H II region identification. Based on the newly derived radio continuum spectra and the evidence of infrared emission, the previously identified SNRs G11.1−1.0, G20.4+0.1 and G16.4−0.5 are believed to be H II regions.

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 A New 1.4 GHz Radio Continuum Map of the Sky South of Declination +25°

2014 ◽  
Vol 31 ◽  
Author(s):  
Mark R. Calabretta ◽  
Lister Staveley-Smith ◽  
David G. Barnes
Keyword(s):  
Large Scale ◽  
Thermal Emission ◽  
High Sensitivity ◽  
Radio Continuum ◽  
Archival Data ◽  
Large Scale Structures ◽  
Low Level ◽  
Sky Survey ◽  
Scale Structures ◽  
Zone Of Avoidance

AbstractArchival data from the HI Parkes All-Sky Survey (HIPASS) and the HI Zone of Avoidance (HIZOA) survey have been carefully reprocessed into a new 1.4 GHz continuum map of the sky south of δ = +25°. The wide sky coverage, high sensitivity of 40 mK (limited by confusion), resolution of 14.4 arcmin (compared to 51 arcmin for the Haslam et al. 408 MHz and 35 arcmin for the Reich et al. 1.4 GHz surveys), and low level of artefacts make this map ideal for numerous studies, including: merging into interferometer maps to complete large-scale structures; decomposition of thermal and non-thermal emission components from Galactic and extragalactic sources; and comparison of emission regions with other frequencies. The new map is available for download.

scholarly journals Radio Continuum Surveys Of The Sky

1988 ◽  
Vol 133 ◽  
pp. 323-329
Author(s):  
R. Wielebinski
Keyword(s):  
Supernova Remnants ◽  
Galactic Plane ◽  
Thermal Emission ◽  
Far Infrared ◽  
Boundary Region ◽  
Radio Continuum ◽  
Relativistic Electrons ◽  
Radio Waves ◽  
Free Process ◽  
Fundamental Information

Radio continuum surveys give us the fundamental information about the distribution of the radio intensity across the sky. The radio waves originate in three fundamental emitting processes and are measured superposed in the antenna beam. At the lowest radio frequencies (below 10 GHz) the nonthermal emission process (synchrotron radiation) predominates. This radio emission comes from supernova remnants, from the “galactic background” (relativistic electrons diffusing in galactic magnetic fields), but also from extragalactic objects (galaxies, quasars, radio galaxies, etc.). In the frequency range 10 GHz < f < 300 GHz the thermal (free-free) process becomes dominant. In the Galaxy we see the HII regions along the galactic plane. In nearby galaxies we can identify the thermal emission in the disks. Above 300 GHz the dust is seen. This is the boundary region between radio and far-infrared radiation.

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 A Detailed Model of the Distribution of Synchrotron Emission in the Galactic Disk

1990 ◽  
Vol 140 ◽  
pp. 61-61
Author(s):  
A. Broadbent ◽  
C.G.T. Haslam ◽  
J.L. Osborne
Keyword(s):  
Magnetic Field ◽  
Galactic Plane ◽  
Galactic Disk ◽  
Cosmic Ray ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Field Variation ◽  
Detailed Model ◽  
Spiral Arm ◽  
Scale Length

A technique for separating the radio continuum emission of the Galaxy into its thermal and nonthermal components has been recently developed by Broadbent, Haslam and Osborne (1989). In this the thermal component is identified by its detailed correlation with the 60 μm infrared emission as observed by IRAS after the subtraction of zodiacal light and the HI-associated dust emission. This technique has been applied to the 408 MHz allsky survey of Haslam et al. (1982). A model of the distribution of synchrotron emissivity in the galactic disk has then been derived including information on the other tracers of spiral structure (HI, CO and giant HII regions) in order to account in detail for the observed nonthermal emission. The spiral arm pattern has two pairs of arms emanating from a central ellipse. The function describing the underlying variation of synchrotron emissivity with galactocentric radius is zero at the centre, rises to a sharp peak and then falls off slowly beyond 3 kpc. Using a scale length of the variation of cosmic ray electron density derived from γ-ray observations, we find that the scale length of the magnetic field variation must be as long as 22 kpc. This agrees with the scale length derived assuming equipartition between energy densities of magnetic field and cosmic rays. The variation of emissivity with height above the plane deduced by Phillipps et al. (1981) when included in our model gives good fits to the observed cuts across the plane. We have modelled the variation of the galactic magnetic field across a spiral arm as a gaussian. In order to fit the peaks in the galactic plane profile σ=0.2 kpc and a maximum compression of the field in the arm of 3.5:1 is required. These parameters are compatible with the results of N-body simulations of spiral arm formation which treat gas clouds as the unit particles. A detailed description of the model is about to be submitted for publication.

Galactic nonthermal radiation. Distribution of SNRs and pulsars

1979 ◽  
Vol 84 ◽  
pp. 113-118
Author(s):  
R. Wielebinski
Keyword(s):  
Supernova Remnants ◽  
Angular Resolution ◽  
Galactic Plane ◽  
Hii Regions ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Nonthermal Radiation ◽  
Radiation Distribution ◽  
Nonthermal Emission ◽  
The Galaxy

All sky surveys of the radio continuum emission give us the basic information on the distribution of the nonthermal emission in the Galaxy. At metre wavelengths, where nonthermal emission is dominant, good angular resolution is difficult to attain. For many years the best surveys near 2 m wavelength gave us a picture of the galaxy with ∼ 2° resolution. At centimetre wavelengths, where arc min resolution is available, the intense HII regions dominate the radio sky. Supernova remnants have a distribution somewhat similar to that of the discrete HII regions and must be delineated by various methods in high resolution galactic plane surveys in the decimetre wavelength range.

Simulated synchrotron emission for the Tycho’s supernova remnants: an asymmetric initial mass model

2020 ◽  
Vol 494 (2) ◽  
pp. 1531-1538
Author(s):  
A Moranchel-Basurto ◽  
P F Velázquez ◽  
G Ares de Parga ◽  
E M Reynoso ◽  
E M Schneiter ◽  
...  
Keyword(s):  
Supernova Remnants ◽  
Brightness Distribution ◽  
Radio Continuum ◽  
Initial Mass ◽  
Continuum Emission ◽  
Synchrotron Emission ◽  
Mass Model ◽  
Mhd Simulations ◽  
Tycho’S Snr ◽  
Good Agreement

ABSTRACT We have performed 3D magnetohydrodynamics (MHD) numerical simulations with the aim of exploring the scenario in which the initial mass distribution of a supernova (SN) explosion is anisotropic. The purpose is to analyse if this scenario can also explain the radio-continuum emission and the expansion observed in young supernova remnants (SNRs). To study the expansion, synthetic polarized synchrotron emission maps were computed from the MHD simulations. We found a good agreement (under a number of assumptions) between this expansion study and previous observational results applied to Tycho’s SNR, which represents a good example of asymmetric young SNRs. Additionally, both the observed morphology and the brightness distribution are qualitatively reproduced.

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