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 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 The HI/OH/Recombination line survey of the inner Milky Way (THOR): data release 2 and H I overview

2020 ◽  
Vol 634 ◽  
pp. A83 ◽  
Author(s):  
Y. Wang ◽  
H. Beuther ◽  
M. R. Rugel ◽  
J. D. Soler ◽  
J. M. Stil ◽  
...  
Keyword(s):  
Optical Depth ◽  
Column Density ◽  
Milky Way ◽  
Angular Resolution ◽  
Galactic Plane ◽  
Continuum Emission ◽  
High Angular Resolution ◽  
Data Release ◽  
Atomic Gas ◽  
Continuum Data

Context. The Galactic plane has been observed extensively by a large number of Galactic plane surveys from infrared to radio wavelengths at an angular resolution below 40′′. However, a 21 cm line and continuum survey with comparable spatial resolution is lacking. Aims. The first half of THOR data (l = 14.0°−37.9°, and l = 47.1°−51.2°, |b|≤ 1.25°) has been published in our data release 1 paper. With this data release 2 paper, we publish all the remaining spectral line data and Stokes I continuum data with high angular resolution (10′′–40′′), including a new H I dataset for the whole THOR survey region (l = 14.0−67.4° and |b|≤ 1.25°). As we published the results of OH lines and continuum emission elsewhere, we concentrate on the H I analysis in this paper. Methods. With the Karl G. Jansky Very Large Array (VLA) in C-configuration, we observed a large portion of the first Galactic quadrant, achieving an angular resolution of ≤40′′. At L Band, the WIDAR correlator at the VLA was set to cover the 21 cm H I line, four OH transitions, a series of Hnα radio recombination lines (RRLs; n = 151 to 186), and eight 128 MHz-wide continuum spectral windows, simultaneously. Results. We publish all OH and RRL data from the C-configuration observations, and a new H I dataset combining VLA C+D+GBT (VLA D-configuration and GBT data are from the VLA Galactic Plane Survey) for the whole survey. The H I emission shows clear filamentary substructures at negative velocities with low velocity crowding. The emission at positive velocities is more smeared-out, likely due to higher spatial and velocity crowding of structures at the positive velocities. Compared to the spiral arm model of the Milky Way, the atomic gas follows the Sagittarius and Perseus Arm well, but with significant material in the inter-arm regions. With the C-configuration-only H I+continuum data, we produce an H I optical depth map of the THOR areal coverage from 228 absorption spectra with the nearest-neighbor method. With this τ map, we corrected the H I emission for optical depth, and the derived column density is 38% higher than the column density with optically thin assumption. The total H I mass with optical depth correction in the survey region is 4.7 × 108 M⊙, 31% more than the mass derived assuming the emission is optically thin. If we applied this 31% correction to the whole Milky Way, the total atomic gas mass would be 9.4–10.5 × 109 M⊙. Comparing the H I with existing CO data, we find a significant increase in the atomic-to-molecular gas ratio from the spiral arms to the inter-arm regions. Conclusions. The high-sensitivity and resolution THOR H I dataset provides an important new window on the physical and kinematic properties of gas in the inner Galaxy. Although the optical depth we derive is a lower limit, our study shows that the optical depth correction issignificant for H I column density and mass estimation. Together with the OH, RRL and continuum emission from the THOR survey, these new H I data provide the basis for high-angular-resolution studies of the interstellar medium in different phases.

scholarly journals The Ratan Galactic Plane Survey

1998 ◽  
Vol 179 ◽  
pp. 103-105
Author(s):  
S.A. Trushkin
Keyword(s):  
Spectral Data ◽  
Supernova Remnants ◽  
Milky Way ◽  
Galactic Plane ◽  
Radio Continuum ◽  
Radio Sources ◽  
Optical Identification ◽  
Source Distance ◽  
The Galaxy

Now in radio continuum surveys more than 10,000 radio sources have discovered in the Milky Way plane but the Galactic origin only of a small part of them has been determined. The problem comes from the absence of estimates of source distance and the optical identification even for bright radio sources, and the most of sources have not spectral data at 2-3 frequencies. As followed some hundreds of sources have not classified as thermal or non-thermal. Now we don't know the full number of supernova remnants (SNRs) in the Galaxy. The simple estimates show that a sample of Galactic SNRs is not full as for weak and extended (> 15′) as for bright and compact (< 3′) SNRs (Trushkin 1993).

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.

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 Characterization of unresolved and unclassified sources detected in radio continuum surveys of the Galactic plane

2020 ◽  
Vol 492 (2) ◽  
pp. 2236-2240
Author(s):  
Arnab Chakraborty ◽  
Nirupam Roy ◽  
Y Wang ◽  
Abhirup Datta ◽  
H Beuther ◽  
...  
Keyword(s):  
Excellent Agreement ◽  
Milky Way ◽  
Galactic Plane ◽  
Large Fraction ◽  
Angular Separation ◽  
Compact Objects ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Extragalactic Radio Source ◽  
Extragalactic Surveys

ABSTRACT The continuum emission from 1 to 2 GHz of The H i/OH/Recombination line survey of the inner Milky Way (THOR) at ≲18 arcsec resolution covers ∼132 deg2 of the Galactic plane and detects 10 387 sources. Similarly, the first data release of the Global View of Star Formation in the Milky Way (GLOSTAR) survey covers ∼16 deg2 of the Galactic plane from 4 to 8 GHz at 18 arcsec resolution and detects 1575 sources. However, a large fraction of the unresolved discrete sources detected in these radio continuum surveys of the Galactic plane remain unclassified. Here, we study the Euclidean-normalized differential source counts of unclassified and unresolved sources detected in these surveys and compare them with simulated extragalactic radio source populations and previously established source counts. We find that the differential source counts for THOR and GLOSTAR surveys are in excellent agreement with both simulation and previous observations. We also estimate the angular two-point correlation function of unclassified and unresolved sources detected in THOR survey. We find a higher clustering amplitude in comparison with the Faint Images of the Radio Sky at Twenty-cm (FIRST) survey up to the angular separation of 5°. The decrease in angular correlation with increasing flux cut and the excellent agreement of clustering pattern of sources above 1 mJy with high-z samples (z &gt; 0.5) of the FIRST survey indicates that these sources might be high-z extragalactic compact objects. The similar pattern of one-point and two-point statistics of unclassified and compact sources with extragalactic surveys and simulations confirms the extragalactic origin of these sources.

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

2020 ◽  
Vol 641 ◽  
pp. C1
Author(s):  
Y. Wang ◽  
S. Bihr ◽  
M. Rugel ◽  
H. Beuther ◽  
K. G. Johnston ◽  
...  
Keyword(s):  
Galactic Plane ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Spectral Indices

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.

scholarly journals Radio observations of evaporating objects in the Cygnus OB2 region

2019 ◽  
Vol 627 ◽  
pp. A58 ◽  
Author(s):  
N. L. Isequilla ◽  
M. Fernández-López ◽  
P. Benaglia ◽  
C. H. Ishwara-Chandra ◽  
S. del Palacio
Keyword(s):  
Thermal Emission ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Spectral Indices ◽  
Ionized Gas ◽  
Low Frequencies ◽  
Thermal Origin ◽  
Index Maps ◽  
Photoionization Rate ◽  
Gas Component

We present observations of the Cygnus OB2 region obtained with the Giant Metrewave Radio Telescope (GMRT) at frequencies of 325 and 610 MHz. In this contribution we focus on the study of proplyd-like objects (also known as free-floating evaporating gas globules or frEGGs) that typically show an extended cometary morphology. We identify eight objects previously studied at other wavelengths and derive their physical properties by obtaining their optical depth at radio-wavelengths. Using their geometry and the photoionization rate needed to produce their radio-continuum emission, we find that these sources are possibly ionized by a contribution of the stars Cyg OB2 #9 and Cyg OB2 #22. Spectral index maps of the eight frEGGs were constructed, showing a flat spectrum in radio frequencies in general. We interpret these as produced by optically thin ionized gas, although it is possible that a combination of thermal emission, not necessarily optically thin, produced by a diffuse gas component and the instrument response (which detects more diffuse emission at low frequencies) can artificially generate negative spectral indices. In particular, for the case of the Tadpole we suggest that the observed emission is not of non-thermal origin despite the presence of regions with negative spectral indices in our maps.

scholarly journals Magnetic Fields and Spiral Structure

1983 ◽  
Vol 100 ◽  
pp. 159-160 ◽  
Author(s):  
R. Beck
Keyword(s):  
Star Formation ◽  
Magnetic Fields ◽  
Milky Way ◽  
Spiral Structure ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Radio Telescopes ◽  
Evolution Of Galaxies ◽  
Structure Strength ◽  
Spiral Structures

Interstellar magnetic fields are known to be a constraint for star formation, but their influence on the formation of spiral structures and the evolution of galaxies is generally neglected. Structure, strength and degree of uniformity of interstellar magnetic fields can be determined by measuring the linearly polarised radio continuum emission at several frequencies (e.g. Beck, 1982). Results for 7 galaxies observed until now with the Effelsberg and Westerbork radio telescopes are given in the table. The Milky Way is also included for comparison.

Sign in / Sign up

Export Citation Format

Share Document