scholarly journals A radio continuum and polarization study of the pulsar wind nebula CTB 87 (G74.9+1.2)

2020 ◽  
Vol 496 (1) ◽  
pp. 723-738
Author(s):  
R Kothes ◽  
W Reich ◽  
S Safi-Harb ◽  
B Guest ◽  
P Reich ◽  
...  
Keyword(s):  
Large Scale ◽  
Galactic Plane ◽  
Low Frequency ◽  
Supernova Explosion ◽  
Radio Continuum ◽  
Polarization Study ◽  
Spectral Break ◽  
Linearly Polarized ◽  
Pulsar Wind ◽  
Cloud Complex

ABSTRACT We present radio continuum and linear polarization observations of the pulsar wind nebula (PWN) CTB 87 (G74.9+1.2) with the Effelsberg 100-m Radio Telescope between 4.75 and 32 GHz. An analysis of these new data including archived low-frequency observations at 1420 and 408 MHz from the Canadian Galactic Plane Survey shows that CTB 87 consists of two distinct emission components: a compact kidney-shaped component, 14 × 8.5 pc2 (7.8 × 4.8 arcmin2) in size and a larger diffuse, spherical, and centrally peaked component of about 30 pc (17 arcmin) in diameter. The kidney-shaped component with a much steeper radio continuum spectrum is highly linearly polarized and likely represents a relic PWN. The diffuse component represents the undisturbed part of the PWN expanding inside a cavity or stellar wind bubble. The previously reported spectral break above 10 GHz is likely the result of missing large-scale emission and insufficient sensitivity of the high-frequency radio continuum observations. The simulation of the system’s evolution yields an age of about 18 000 yr as the result of a Type II supernova explosion with ejecta mass of about 12 M⊙ and explosion energy of about 7 × 1050 erg. We also found evidence for a radio shell in our polarization data that represents the blast wave that entered the molecular cloud complex at a radius of about 13 pc.

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.

scholarly journals CHANG-ES XII

2019 ◽  
Vol 622 ◽  
pp. A9 ◽  
Author(s):  
A. Miskolczi ◽  
V. Heesen ◽  
C. Horellou ◽  
D.-J. Bomans ◽  
R. Beck ◽  
...  
Keyword(s):  
Spectral Index ◽  
Large Scale ◽  
Low Frequency ◽  
Cosmic Ray ◽  
Radio Continuum ◽  
Dark Matter Halo ◽  
Very Large Array ◽  
Star Forming ◽  
Pure Diffusion ◽  
The Galaxy

Context. Low-frequency radio continuum studies of star-forming edge-on galaxies can help to further understand how cosmic-ray electrons (CRe) propagate through the interstellar medium into the halo and how this is affected by energy losses and magnetic fields. Aims. Observations with the Very Large Array (VLA) from Continuum Haloes in Nearby Galaxies – an EVLA Survey (CHANG-ES) are combined with those with the LOw Frequency ARray (LOFAR) from the LOFAR Two-metre Sky Survey (LoTSS ) to identify the prevailing mode of cosmic-ray transport in the edge-on spiral galaxy NGC 3556. Methods. We mapped the radio spectral index, magnetic field strength, and orientation using VLA 1.5 and 6 GHz and LOFAR 144 MHz data, and we fit 1D cosmic-ray propagation models to these maps using SPINNAKER (Spectral Index Numerical Analysis of K(c)osmic-ray electron radio emission) and its interactive wrapper SPINTERACTIVE. Results. We find that the spectral index in the galactic midplane is, as expected for young CRe, α ≈ −0.7 and steepens towards the halo of the galaxy as a consequence of spectral ageing. The intensity scale heights are about 1.4 and 1.9 kpc for the thin disc, and 3.3 and 5.9 kpc for the thick disc at 1.5 GHz and 144 MHz, respectively. While pure diffusion cannot explain our data, advection can, particularly if we assume a linearly accelerating wind. Our best-fitting model has an initial speed of 123 km s−1 in the galactic midplane and reaches the escape velocity at heights between 5 kpc and 15 kpc above the disc, depending on the assumed dark matter halo of the galaxy. This galactic wind scenario is corroborated by the existence of vertical filaments seen both in the radio continuum and in H α in the disc-halo interface and of a large-scale reservoir of hot, X-ray emitting gas in the halo. Conclusions. Radio haloes show the existence of galactic winds, possibly driven by cosmic rays, in typical star-forming spiral galaxies.

scholarly journals On the nature of radio filaments near the Galactic Centre

2019 ◽  
Vol 489 (1) ◽  
pp. L28-L31 ◽  
Author(s):  
Maxim V Barkov ◽  
Maxim Lyutikov
Keyword(s):  
Large Scale ◽  
Low Frequency ◽  
High Energy ◽  
Point Sources ◽  
Galactic Centre ◽  
Pulsar Wind Nebulae ◽  
Flux Tubes ◽  
Inverse Compton Scattering ◽  
Inverse Compton ◽  
Pulsar Wind

ABSTRACT We suggest that narrow, long radio filaments near the Galactic Centre arise as kinetic jets – streams of high-energy particles escaping from ram pressure confined pulsar wind nebulae (PWNe). The reconnection between the PWN and interstellar magnetic field allows pulsar wind particles to escape, creating long narrow features. They are the low-frequency analogues of kinetic jets seen around some fast-moving pulsars, such as The Guitar and The Lighthouse PWNe. The radio filaments trace a population of pulsars also responsible for the Fermi GeV excess produced by the Inverse Compton scattering by the pulsar wind particles. The magnetic flux tubes are stretched radially by the large-scale Galactic winds. In addition to PWNe accelerated particles can be injected at supernovae remnants. The model predicts variations of the structure of the largest filaments on scales of ∼dozens of years – smaller variations can occur on shorter time-scales. We also encourage targeted observations of the brightest sections of the filaments and of the related unresolved point sources in search of the powering PWNe and pulsars.

scholarly journals Galactic Fine Structure at 843 MHz

1996 ◽  
Vol 169 ◽  
pp. 611-612
Author(s):  
A.J. Green ◽  
D. Campbell-Wilson ◽  
L.E. Cram ◽  
M.I. Large ◽  
B. Piestrzynski ◽  
...  
Keyword(s):  
Fine Structure ◽  
Galactic Plane ◽  
Low Frequency ◽  
Scale Structure ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Fine Scale

The Southern Galactic Plane surveyed by the Molonglo Observatory Synthesis Telescope (MOST) gives an unprecedented view of fine-scale structure in low frequency radio continuum emission over the area 245° ≤ l ≤ 355°, |b| ≤ 1.5°. The telescope operates at 843 MHz with a resolution of 43″ and a sensitivity of approximately 2 mJy/beam for the sample region (5° × 3°), centred on G317.5+0.0, presented here to illustrate significant features in the sources. This is a mosaic of 35 fields, each representing a 12 hr observation.

The Marseille Observatory Hα Survey: Comparisons by CO, 6 CM and IRAS Data

1998 ◽  
Vol 179 ◽  
pp. 186-188
Author(s):  
D. Russeil ◽  
P. Amram ◽  
Y.P. Georgelin ◽  
Y.M. Georgelin ◽  
M. Marcelin ◽  
...  
Keyword(s):  
Molecular Cloud ◽  
Large Scale ◽  
Galactic Plane ◽  
Photon Counting ◽  
Hii Regions ◽  
Radio Continuum ◽  
Line Of Sight ◽  
Ionized Gas ◽  
Hii Region ◽  
Pattern Determination

The Marseille Observatory Hα survey supplies Hα velocities of the ionized hydrogen over large zones of the sky towards the galactic plane. This survey, led at the ESO La Silla, uses a 36 cm telescope equiped with a scanning Fabry-Perot interferometer and a photon counting camera (Le Coarer et al. 1992). About 250 fields (39′×39′) toward the galactic plane have already been covered (see Figure 1) with a spatial resolution of 9″×9″ and a spectral resolution of 5 km s–1. This allows us to observe the discrete HII regions and the diffuse ionized gas widely distributed between them and to separate the distinct layers found along the line of sight. HII regions are often grouped on the molecular cloud surface, then CO, radio continuum and recombination lines surveys of the galactic plane are also essential to distinguish the HII region-molecular cloud complexes met on the line of sight, and in order to take dynamical effects into account, such as the champagne effect, for the kinematic distance determination. Indeed, the spiral structure pattern determination requires avoiding any artificial spread by clearly identifying the giant complexes composed of molecular clouds, HII regions, diffuse ionized hydrogen widely surrounding them, and exciting stars. On the other hand the ionized gas data (Hα and recombination lines) associated with IRAS data help us to study the nature of the young objects constituent of these complexes and to assess their detectability. We present two fields from the Hα survey and parallel large scale investigations.

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.

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 Boomerang: A Crushed and Re-born PWN?

2004 ◽  
Vol 218 ◽  
pp. 213-214
Author(s):  
Roland Kothes ◽  
Bülent Uyaniker ◽  
Wolfgang Reich
Keyword(s):  
Shock Wave ◽  
Radio Telescope ◽  
Galactic Plane ◽  
Low Frequency ◽  
Radio Spectrum ◽  
Frequency Data ◽  
Radio Luminosity ◽  
Reverse Shock ◽  
Pulsar Wind ◽  
5 Ghz

We present new high radio frequency observations of the Boomerang pulsar wind nebula (PWN) made with the Effelsberg 100-m radio telescope. A comparison with low frequency data from the Canadian Galactic Plane Survey (CGPS; Taylor et al. 2003) reveals a change of the nebula's emission structure with frequency caused by a radial steepening of the radio spectrum above 5 GHz. We also find evidence that the reverse shock of the initial supernova shock wave has driven away or crushed the original PWN which might explain why the current nebula around the pulsar has such a low radio luminosity.

scholarly journals FOREST unbiased Galactic plane imaging survey with the Nobeyama 45 m telescope (FUGIN). VI. Dense gas and mini-starbursts in the W 43 giant molecular cloud complex

2020 ◽  
Author(s):  
Mikito Kohno ◽  
Kengo Tachihara ◽  
Kazufumi Torii ◽  
Shinji Fujita ◽  
Atsushi Nishimura ◽  
...  
Keyword(s):  
Molecular Cloud ◽  
Large Scale ◽  
Galactic Plane ◽  
High Mass ◽  
Mass Star ◽  
Dense Gas ◽  
Star Forming ◽  
Star Forming Regions ◽  
Giant Molecular Cloud ◽  
Cloud Complex

Abstract We performed new large-scale 12CO, 13CO, and C18O J = 1–0 observations of the W 43 giant molecular cloud complex in the tangential direction of the Scutum arm (l ∼30°) as a part of the FUGIN project. The low-density gas traced by 12CO is distributed over 150 pc × 100 pc (l × b), and has a large velocity dispersion (20–30 km s−1). However, the dense gas traced by C18O is localized in the W 43 Main, G30.5, and W 43 South (G29.96−0.02) high-mass star-forming regions in the W 43 giant molecular cloud (GMC) complex, which have clumpy structures. We found at least two clouds with a velocity difference of ∼10–20 km s−1, both of which are likely to be physically associated with these high-mass star-forming regions based on the results of high 13CO J = 3–2 to J = 1–0 intensity ratio and morphological correspondence with the infrared dust emission. The velocity separation of these clouds in W 43 Main, G30.5, and W 43 South is too large for each cloud to be gravitationally bound. We also revealed that the dense gas in the W 43 GMC has a high local column density, while “the current SFE” (star formation efficiency) of the entire GMC is low ($\sim\!\! 4\%$) compared with the W 51 and M 17 GMC. We argue that the supersonic cloud–cloud collision hypothesis can explain the origin of the local mini-starbursts and dense gas formation in the W 43 GMC complex.

scholarly journals Reliable detection and characterization of low-frequency polarized sources in the LOFAR M51 field

2018 ◽  
Vol 617 ◽  
pp. A136 ◽  
Author(s):  
A. Neld ◽  
C. Horellou ◽  
D. D. Mulcahy ◽  
R. Beck ◽  
S. Bourke ◽  
...  
Keyword(s):  
False Discovery Rate ◽  
Broad Band ◽  
Low Frequency ◽  
Large Data ◽  
Radio Continuum ◽  
Data Sets ◽  
Nearby Galaxy ◽  
Data Set ◽  
False Discovery ◽  
Linearly Polarized

Context. The new generation of broad-band radio continuum surveys will provide large data sets with polarization information. New algorithms need to be developed to extract reliable catalogs of linearly polarized sources that can be used to characterize those sources and produce a dense rotation measure (RM) grid to probe magneto-ionized structures along the line of sight via Faraday rotation. Aims. The aim of the paper is to develop a computationally efficient and rigorously defined source-finding algorithm for linearly polarized sources. Methods. We used a calibrated data set from the LOw Frequency ARray (LOFAR) at 150 MHz centered on the nearby galaxy M 51 to search for polarized background sources. With a new imaging software, we re-imaged the field at a resolution of 18″ × 15″ and cataloged a total of about 3000 continuum sources within 2.5° of the center of M 51. We made small Stokes Q and U images centered on each source brighter than 100 mJy in total intensity (201 sources) and used RM synthesis to create corresponding Faraday cubes that were analyzed individually. For each source, the noise distribution function was determined from a subset of the measurements at high Faraday depths where no polarization is expected; the peaks in polarized intensity in the Faraday spectrum were identified and the p-value of each source was calculated. Finally, the false discovery rate method was applied to the list of p-values to produce a list of polarized sources and quantify the reliability of the detections. We also analyzed sources fainter than 100 mJy but that were reported as polarized in the literature at at least another radio frequency. Results. Of the 201 sources that were searched for polarization, six polarized sources were detected confidently (with a false discovery rate of 5%). This corresponds to a number density of one polarized source per 3.3 square degrees, or 0.3 source per square degree. Increasing the false discovery rate to 50% yields 19 sources. A majority of the sources have a morphology that is indicative of them being double-lobed radio galaxies, and the ones with literature redshift measurements have 0.5 < z < 1.0. Conclusions. We find that this method is effective in identifying polarized sources, and is well suited for LOFAR observations. In the future, we intend to develop it further and apply it to larger data sets such as the LOFAR Two-meter Survey of the whole northern sky, LOTSS, and the ongoing deep LOFAR observations of the GOODS-North field.

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