- ID:
- ivo://CDS.VizieR/J/ApJS/194/31
- Title:
- Morphology for groups in the FIRST database
- Short Name:
- J/ApJS/194/31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The morphology of selected groups of sources in the Faint Images of the Radio Sky at Twenty Centimeters (FIRST) survey and catalog is examined. Sources in the FIRST catalog (2003 April release, 811117 entries) were sorted into singles, doubles, triples, and groups of higher-count membership based on a proximity criteria. The 7106 groups with four or more components were examined individually for bent types including, but not limited to, wide-angle tail and narrow-angle tail types. In the process of this examination, ring, double-double, X-shaped, hybrid morphology, giant radio sources, and the herein described W-shaped and tri-axial morphology systems were also identified. For the convenience of the reader separate tables for distinctive types were generated. A few curiosities were found. For the 16950 three-component groups and 74788 two-component groups, catalogs with probability estimates for bent classification, as determined by pattern recognition techniques, are presented.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/571/A61
- Title:
- M31 polarization & magnetic structure
- Short Name:
- J/A+A/571/A61
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Andromeda Galaxy (M31) is the nearest grand-design spiral galaxy. Thus far, most studies in the radio regime concentrated on the 10kpc ring. The central region of M31 has significantly different properties than the outer parts: The star formation rate is low, and inclination and position angle are largely different from the outer disk. The existing model of the magnetic field in the radial range 6<=r<=14kpc is extended to the innermost part r<=0.5kpc to ultimately achieve a picture of the entire magnetic field in M 31. We combined observations taken with the VLA at 3.6cm and 6.2cm with data from the Effelsberg 100-m telescope to fill the missing spacings of the synthesis data. The resulting polarization maps were averaged in sectors to analyse the azimuthal behaviour of the polarized intensity (PI), rotation measure (RM), and apparent pitch angle ({phi}_obs_). We developed a simplified 3D model for the magnetic field in the central region to explain the azimuthal behaviour of the three observables. Our 3D model of a quadrupolar or dipolar dynamo field can explain the observed patterns in PI, RM, and {phi}_obs_, while a 2D configuration is not sufficient to explain the azimuthal behaviour. In addition and independent of our model, the RM pattern shows that the spiral magnetic field in the inner 0.5kpc points outward, which is opposite to that in the outer disk, and has a pitch angle of =~33{deg}, which is much larger than that of 8{deg}-19{deg} in the outer disk. The physical conditions in the central region differ significantly from those in the 10kpc ring. In addition, the orientation of this region with respect to the outer disk is completely different. The opposite magnetic field directions suggest that the central region is decoupled from the outer disk, and we propose that an independent dynamo is active in the central region.
- ID:
- ivo://CDS.VizieR/J/A+A/588/A114
- Title:
- M101 radio polarization & magnetic structure
- Short Name:
- J/A+A/588/A114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We observed total and polarized radio continuum emission from the spiral galaxy M 101 at {lambda}{lambda}6.2cm and 11.1cm with the Effelsberg telescope. The angular resolutions are 2.5' (=5.4kpc) and 4.4' (=9.5kpc), respectively. We use these data to study various emission components in M 101 and properties of the magnetic field. Separation of thermal and non-thermal emission shows that the thermal emission is closely correlated with the spiral arms, while the non-thermal emission is more smoothly distributed indicating di ff usion of cosmic ray electrons away from their places of origin. The radial distribution of both emissions has a break near R=16kpc (=7.4'), where it steepens to an exponential scale length of L=~5kpc, which is about 2.5 times smaller than at R<16kpc. The distribution of the polarized emission has a broad maximum near R=12kpc and beyond R=16kpc also decreases with L=~5kpc. It seems that near R=16kpc a major change in the structure of M 101 takes place, which also a ff ects the distributions of the strength of the random and ordered magnetic field. Beyond R=16kpc the radial scale length of both fields is about 20kpc, which implies that they decrease to about 0.3uG at R=70kpc, which is the largest optical extent. The equipartition strength of the total field ranges from nearly 10uG at R<2kpc to 4uG at R=22-24kpc. As the random field dominates in M 101 (B_ran_/B_ord_=~2.4), wavelength-independent polarization is the main polarization mechanism. We show that energetic events causing H i shells of mean diameter <625pc could partly be responsible for this. At radii <24kpc, the random magnetic field depends on the star formation rate/area, {Sigma}_SFR_, with a power-law exponent of b=0.28+/-0.02. The ordered magnetic field is generally aligned with the spiral arms with pitch angles that are about 8{deg} larger than those of HI filaments.
- ID:
- ivo://CDS.VizieR/J/MNRAS/431/1107
- Title:
- M82 radio sources flux density variations
- Short Name:
- J/MNRAS/431/1107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents the results of the 2009-2010 monitoring sessions of the starburst galaxy M82, obtained with the Multi-Element Radio-Linked Interferometer Network (MERLIN) at 5GHz and e-MERLIN at 6GHz. Combining several 5GHz MERLIN epochs to form a map with 33.0{mu}Jy/bm noise level, 52 discrete sources, mostly supernova remnants and HII regions, are identified. These include three objects which were not detected in the 2002 5GHz MERLIN monitoring session: supernova SN2008iz, the transient source 43.78+59.3, and a new supernova remnant shell. Flux density variations, in the long (1981 to 2010), medium (2002 to 2010) and short (2009 to 2010) term are investigated. We find that flux densities of supernova remnants (SNRs) in M82 stay constant in most of the sample (~95 per cent), although the distributions of flux density variations show an offset from zero. This is consistent with a slight statistical reduction in flux density of the source distribution. In addition, aside from SN2008iz and the well-known variable source 41.95+57.5, two sources display tentative evidence for short- and medium-term variations over the period 2009-2010. These sources are amongst the most compact SNR in M82. These flux density variations could be due to changes in the circumstellar and interstellar medium in which the shocks travel.
- ID:
- ivo://CDS.VizieR/J/A+A/655/A89
- Title:
- Mrk421 multi-instrument observations in 2017
- Short Name:
- J/A+A/655/A89
- Date:
- 21 Mar 2022 08:46:33
- Publisher:
- CDS
- Description:
- We present a detailed characterisation and theoretical interpretation of the broadband emission of the paradigmatic TeV blazar Mrk 421, with a special focus on the multi-band flux correlations. The dataset has been collected through an extensive multi-wavelength campaign organised between 2016 December and 2017 June. The instruments involved are MAGIC, FACT, Fermi-LAT, Swift, GASP-WEBT, OVRO, Medicina, and Metsahovi. Additionally, four deep exposures (several hours long) with simultaneous MAGIC and NuSTAR observations allowed a precise measurement of the falling segments of the two spectral components. The very-high-energy (VHE; E>100GeV) gamma rays and X-rays are positively correlated at zero time lag, but the strength and characteristics of the correlation change substantially across the various energy bands probed. The VHE versus X-ray fluxes follow different patterns, partly due to substantial changes in the Compton dominance for a few days without a simultaneous increase in the X-ray flux (i.e. orphan gamma-ray activity). Studying the broadband spectral energy distribution (SED) during the days including NuSTAR observations, we show that these changes can be explained within a one-zone leptonic model with a blob that increases its size over time. The peak frequency of the synchrotron bump varies by two orders of magnitude throughout the campaign. Our multi-band correlation study also hints at an anti-correlation between UV-optical and X-ray at a significance higher than 3{sigma}. A VHE flare observed on MJD~57788 (2017 February 4) shows gamma-ray variability on multi-hour timescales, with a factor ten increase in the TeV flux but only a moderate increase in the keV flux. The related broadband SED is better described by a two-zone leptonic scenario rather than by a one-zone scenario. We find that the flare can be produced by the appearance of a compact second blob populated by high energetic electrons spanning a narrow range of Lorentz factors, from {gamma}'_min_=2x10^4^ to {gamma}'_max_=6x10^5^.
- ID:
- ivo://CDS.VizieR/J/A+A/593/A91
- Title:
- Mrk 421 multi-wavelength variability, 2007-2009
- Short Name:
- J/A+A/593/A91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We perform an extensive multi-band variability and correlation study of the TeV blazar Mrk 421 on year time scales, which can bring additional insight on the processes responsible for its broadband emission. We observed Mrk 421 in the very high energy gamma-ray range with the Cherenkov telescope MAGIC-I from March 2007 to June 2009. The 2.3-year long MAGIC light curve is complemented with data from the Swift/BAT and RXTE/ASM satellites and the KVA, GASP-WEBT, OVRO, and Metsahovi telescopes from February 2007 to July 2009, allowing for an excellent characterisation of the multi-band variability and correlations over year time scales.
- ID:
- ivo://CDS.VizieR/J/A+A/484/119
- Title:
- Multi-epoch VLBI survey of CJF sources
- Short Name:
- J/A+A/484/119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the second in a series of papers presenting VLBI observations of the 293 Caltech-Jodrell Bank Flat-spectrum (hereafter CJF) sources and their analysis. We obtain a consistent motion dataset large enough to allow the systematic properties of the population to be studied. We present detailed kinematic analysis of the complete flux-density limited CJF survey. We computed 2-D kinematic models based on the optimal model-fitting parameters of multi-epoch VLBA observations. This allows us to calculate not only radial, but also orthogonal motions, and thus to study curvature and acceleration. Statistical tests of the motions measured and their reliability were performed. A correlation analysis between the derived apparent motions, luminosities, spectral indices, and core dominance and the resulting consequences is described. With at least one velocity in each of the 237 sources, this sample is much larger than any available before, so it allows a meaning ful statistical investigation of apparent motions and any possible correlations with other parameters in AGN jets. The main results to emerge are as follows: * In general motions are not consistent with a single uniform velocity applicable to all components along a jet. * We find a slight trend towards a positive outward acceleration and also adduce some evidence for greater acceleration in the innermost regions. * We find a lack of fast components at physical distances less than a few pc from the reference feature. * Only ~4% of the components from galaxies and <2% of those from quasars undergo large bends i.e. within 15{deg} of +/-90{deg}. * The distribution of radial velocities shows a broad distribution of velocities (apparent velocities up to 30c). Fifteen percent of the best-sampled jet components exhibit low velocities that may need to be explained in a different manner to the fast motions. * Some negative superluminal motions are seen, and in 15 cases (6%) these are definitely significant. * We find a strong correlation between the 5 GHz luminosity and the apparent velocity. * The CJF galaxies, on average, show slower apparent jet-component velocities than the quasars. * The mean velocity in the VLBA 2cm survey (Kellermann et al. 2004) is substantially higher than in the CJF survey, the ratio could be roughly a factor of 1.5-2. This supports the observed trend toward increasing apparent velocity with in creasing observing frequency. This AGN survey provides the basis for any statistical analysis of jet and jet-component properties.
- ID:
- ivo://CDS.VizieR/J/A+A/472/763
- Title:
- Multi-epoch VLBI survey of CJF sources
- Short Name:
- J/A+A/472/763
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Global VLBI and VLBA observations (5GHz) of 293 sources of the CJF-sample have been conducted between 1990 and 2001. In total, thirteen separate observing campaigns have been accumulated. File table2.dat contains results from model-fitting Gaussian components to the data. We list the parameters for 288 sources in Table 2. fig directory contains the corresponding images, built up by restoring the model-fitted components, convolved with the clean beam, into the residual image, which was made by Fourier transforming the visibility data after first subtracting the model-fitted components in the uv-plane. Over-plotted we show symbols to represent the model components.
- ID:
- ivo://CDS.VizieR/J/MNRAS/273/411
- Title:
- Multifrequency fluxes of 280 pulsars
- Short Name:
- J/MNRAS/273/411
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Table3 contains the flux density measurements of pulsars made at radio frequencies centred around 408, 606, 925, 1408 and 1606MHz using the 76-m Lowell telescope at Jodrell Bank. The observations have been made over a period of more than 3 years and concern 280 pulsars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/379/1442
- Title:
- Multifrequency observations of 9C sources
- Short Name:
- J/MNRAS/379/1442
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used multifrequency follow-up observations of a sample of extragalactic sources from the 9C survey at 15GHz to make deductions about the expected source population at higher radio frequencies, such as those in the lower frequency bands of the Planck Surveyor satellite. In particular, we have made empirical estimates of the source counts at 22, 30, 43 and 70GHz and compared these with both known data and current theoretical predictions. We have also made an estimate of the count at the Atacama Large Millimeter Array (ALMA) frequency of 90GHz, with a view to assessing the possible population of point sources available for the phase calibration of that instrument.
