Radio Continuum Emission of the Milky Way and Nearby Galaxies

1985 ◽  
pp. 239-244 ◽  
Author(s):  
Rainer Beck ◽  
Wolfgang Reich
Keyword(s):  
Milky Way ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Nearby Galaxies

scholarly journals Radio continuum emission of the Milky Way and nearby galaxies

1985 ◽  
Vol 106 ◽  
pp. 239-244 ◽  
Author(s):  
Rainer Beck ◽  
Wolfgang Reich
Keyword(s):  
Magnetic Field ◽  
Central Region ◽  
Milky Way ◽  
Thin Disk ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Spiral Arms ◽  
Ordered Field ◽  
Nearby Galaxies ◽  
The Magnetic Field

The radio continuum emission of the Milky Way and nearby galaxies can be decomposed into a central region, a clumpy “thin disk”, concentrated in the spiral arms, and a smooth “thick disk” (or flattened “halo”). The emissivity ratio of the two disks seems to be related to the magnetic field properties: Galaxies with strong radio spiral arms reveal a highly ordered field following the arm direction, while galaxies with diffuse disks contain a less ordered, smoothly distributed field. The degree of uniformity of the field seems to correlate with the total optical luminosity. The average magnetic field in the Milky Way is weak and turbulent compared to most of the nearby galaxies observed so far.

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.

scholarly journals The resolved radio–FIR correlation in nearby galaxies with Herschel and Spitzer

2011 ◽  
Vol 7 (S284) ◽  
pp. 400-403
Author(s):  
Fatemeh S. Tabatabaei ◽  
Eva Schinnerer ◽  
Eric Murphy ◽  
Rainer Beck ◽  
Annie Hughes ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Diffusion Length ◽  
Spatial Scales ◽  
Cosmic Ray ◽  
Far Infrared ◽  
Scale Dependence ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Synchrotron Emission ◽  
Nearby Galaxies

AbstractWe investigate the correlation between the far-infrared (FIR) and radio continuum emission from NGC6946 on spatial scales between 0.9 and 17 kpc. We use the Herschel PACS (70, 100, 160μm) and SPIRE (250μm) data from the KINGFISH project. Separating the free-free and synchrotron components of the radio continuum emission, we find that FIR is better correlated with the free-free than the synchrotron emission. Compared to a similar study in M33 and M31, we find that the scale dependence of the synchrotron–FIR correlation in NGC6946 is more similar to M31 than M33. The scale dependence of the synchrotron–FIR correlation can be explained by the turbulent-to-ordered magnetic field ratio or, equivalently, the diffusion length of the cosmic ray electrons in these galaxies.

scholarly journals Magnetism in galaxies – Observational overview and next generation radio telescopes

2010 ◽  
Vol 6 (S274) ◽  
pp. 325-332 ◽  
Author(s):  
Rainer Beck
Keyword(s):  
Magnetic Fields ◽  
Faraday Rotation ◽  
Large Scale ◽  
Milky Way ◽  
Cosmic Ray ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Radio Telescopes ◽  
Spiral Arms ◽  
Central Regions

AbstractThe strength and structure of cosmic magnetic fields is best studied by observations of radio continuum emission, its polarization and its Faraday rotation. Fields with a well-ordered spiral structure exist in many types of galaxies. Total field strengths in spiral arms and bars are 20–30 μG and dynamically important. Strong fields in central regions can drive gas inflows towards an active nucleus. The strongest regular fields (10–15 μG) are found in interarm regions, sometimes forming “magnetic spiral arms” between the optical arms. The typical degree of polarization is a few % in spiral arms, but high (up to 50%) in interarm regions. The detailed field structures suggest interaction with gas flows. Faraday rotation measures of the polarization vectors reveals large-scale patterns in several spiral galaxies which are regarded as signatures of large-scale (coherent) fields generated by dynamos. – Polarization observations with the forthcoming large radio telescopes will open a new era in the observation of magnetic fields and should help to understand their origin. Low-frequency radio synchrotron emission traces low-energy cosmic ray electrons which can propagate further away from their origin. LOFAR (30–240 MHz) will allow us to map the structure of weak magnetic fields in the outer regions and halos of galaxies, in galaxy clusters and in the Milky Way. Polarization at higher frequencies (1–10 GHz), to be observed with the EVLA, MeerKAT, APERTIF and the SKA, will trace magnetic fields in the disks and central regions of galaxies in unprecedented detail. All-sky surveys of Faraday rotation measures towards a dense grid of polarized background sources with ASKAP and the SKA are dedicated to measure magnetic fields in distant intervening galaxies and clusters, and will be used to model the overall structure and strength of the magnetic field in the Milky Way.

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 Radio Emission from Nearby Galaxies at High Frequencies

1981 ◽  
Vol 94 ◽  
pp. 225-226
Author(s):  
Rainer Beck ◽  
Ulrich Klein
Keyword(s):  
High Resolution ◽  
High Frequency ◽  
Spiral Galaxies ◽  
Low Frequency ◽  
Cosmic Ray ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Frequency Synthesis ◽  
High Frequencies ◽  
Nearby Galaxies

High resolution observations of the radio continuum emission from nearby galaxies at several frequencies provide information about the cosmic ray electrons. Optimum results are expected by combining low-frequency synthesis observations with high-frequency single dish data, e.g. Westerbork 610 MHz / Effelsberg 10.7 GHz (1′ resolution) or Cambridge 150 MHz / Effelsberg 2.7 GHz (4′ resolution). Maps of 15 nearby spiral galaxies at 10.7 GHz have been made with the Effelsberg 100-m telescope. Maps of M31 and M33 are available at 2.7 and 4.8 GHz.

scholarly journals CHANG-ES: XVIII—The CHANG-ES Survey and Selected Results

Galaxies ◽  
2019 ◽  
Vol 7 (1) ◽  
pp. 42 ◽  
Author(s):  
Judith Irwin ◽  
Ancor Damas-Segovia ◽  
Marita Krause ◽  
Arpad Miskolczi ◽  
Jiangtao Li ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Polarization Data ◽  
Wide Range ◽  
Nearby Galaxies ◽  
Broad Scale

The CHANG-ES (Continuum Halos in Nearby Galaxies) survey of 35 nearby edge-on galaxies is revealing new and sometimes unexpected and startling results in their radio continuum emission. The observations were in wide bandwidths centred at 1.6 and 6.0 GHz. Unique to this survey is full polarization data showing magnetic field structures in unprecedented detail, resolution and sensitivity for such a large sample. A wide range of new results are reported here, some never before seen in any galaxy. We see circular polarization and variability in active galactic nuclei (AGNs), in-disk discrete features, disk-halo structures sometimes only seen in polarization, and broad-scale halos with reversing magnetic fields, among others. This paper summarizes some of the CHANG-ES results seen thus far.

scholarly journals Modeling the 60μm/20cm Infrared-to-Radio Ratio Within Spiral Galaxies

1990 ◽  
Vol 140 ◽  
pp. 237-238
Author(s):  
M. D. Bicay ◽  
G. Helou
Keyword(s):  
Spiral Galaxies ◽  
Far Infrared ◽  
Major Axis ◽  
Detailed Comparison ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Local Maxima ◽  
Central Regions ◽  
Order Of Magnitude ◽  
Nearby Galaxies

The remarkably tight global correlation between integrated far-infrared and radio continuum emission from spiral galaxies has recently stimulated interest in determining whether the relation holds spatially within galaxies (Wainscoat et al. 1987; Beck and Golla 1988; Bicay et al. 1989, hereafter Paper I). We report here on a detailed comparison of the distribution of 60μm infrared and 20cm radio continuum emission within 25 galaxies, mostly disk spirals. Local maxima in the thermal infrared and predominantly nonthermal radio maps are found to be spatially coincident on scales <0.3h−1 kpc in nearby galaxies. Superimposed on this broad correlation, we observe in the disks of most sample galaxies a slow decrease in the 60μm-to-20cm ratio Q60 with increasing radius. Values of Q60 within the central regions are often enhanced by a factor of 3 or more compared to the outer disks, whereas the corresponding enhancement in radio surface brightness is greater by at least an order of magnitude. The radial gradient in Q60 is most easily identified in nearby, face-on galaxies (e.g. NGC 5236, NGC 6946) due to the limited IRAS angular resolution. However, the gradient is also observed along the major axis of highly inclined systems (e.g. NGC 55).

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