- 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.
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- 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/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/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.
- ID:
- ivo://CDS.VizieR/J/A+AS/106/303
- Title:
- Multifrequency observations of ROSAT sources
- Short Name:
- J/A+AS/106/303
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on results of multifrequency radio continuum observations with the Effelsberg 100-m telescope of 234 radio sources which have counterparts in the ROSAT all-sky survey. Observations have been made at 21 cm, 11 cm, 6 cm and 2.8 cm wavelength in the flux density range above 20 mJy. We have determined the spectrum, size, linear polarization and improved positions of these sources. We give the statistical properties of the ROSAT selected radio sources and compare them with results from unbiased radio source surveys so far available.
- ID:
- ivo://CDS.VizieR/J/MNRAS/301/235
- Title:
- Multifrequency polarimetry of 300 pulsars
- Short Name:
- J/MNRAS/301/235
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Polarimetric observations of 300 pulsars have been conducted with the 76-m Lovell telescope at Jodrell Bank at radio frequencies centred around 230, 400, 600, 920, 1400 and 1600MHz. More than half of the pulsars have no previously published polarization profiles and this compilation represents about three times the sum of all previously published pulsar polarization data. A selection of integrated polarization profiles is provided. Tables of pulse widths and the degree of both linear and circular polarization are given for all pulsars, and these act as an index for all the data, which are available by anonymous ftp in numerical and graphical form.
- ID:
- ivo://CDS.VizieR/J/A+A/573/A76
- Title:
- Multifrequency study of NL Seyfert 1 galaxies
- Short Name:
- J/A+A/573/A76
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High-energy {gamma}-rays, which are produced by powerful relativistic jets, are usually associated with blazars and radio galaxies. In the current active galactic nuclei (AGN) paradigm, such jets are almost exclusively launched from massive elliptical galaxies. Recently, however, Fermi/LAT detected {gamma}-rays from a few narrow-line Seyfert 1 galaxies and thus confirmed the presence of relativistic jets in them. Since NLS1 galaxies are assumed to be young evolving AGN, they offer a unique opportunity to study the production of relativistic jets in late-type galaxies. Our aim is to estimate by which processes the emission of various kinds is produced in NLS1 galaxies and to study how emission properties are connected to other intrinsic AGN properties. We have compiled the so far largest multiwavelength database of NLS1 sources. This allowed us to explore correlations between different wavebands and source properties using, for example, Pearson and Spearman correlations and principal component analysis. We did this separately for radio-loud and radio-quiet sources.
- ID:
- ivo://CDS.VizieR/J/other/Ser/166.13
- Title:
- Multi-frequency study of the Pavo field
- Short Name:
- J/other/Ser/166.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We test the prediction of Hamilton and Helfand (<A HREF="http://simbad.cds.unistra.fr/simbad/sim-ref?bibcode=1993ApJ...418...55H%201993ApJ...418...55H">1993ApJ...418...55H 1993ApJ...418...55H</A>) that faint radio selected galaxies are a new class contributing to the diffuse X-ray background (XRB) radiation. The test is based on the correlation of X-ray, optical and radio positions for sources detected in ROSAT (S<SUB>0.08–2.4keV</SUB>>6x10<SUP>–15</SUP>erg/s/cm<SUP>2</SUP>, 69 sources) and ATCA (S<SUB>1.42GHz</SUB>>250uJy, 93 sources) observations of the Einstein Pavo field. A total of six ATCA radio sources inside the inner ring of the ROSAT image are located within 10" of the ROSAT X-ray positions, with one associated by random chance.
- ID:
- ivo://CDS.VizieR/J/A+A/392/795
- Title:
- Multi-wavelength study of 2 galaxy clusters
- Short Name:
- J/A+A/392/795
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from optical, X-ray and radio observations of two X-ray bright (L_X_~10^45^erg/s) galaxy clusters. Abell 1451 is at redshift z=0.1989 and has line-of-sight velocity dispersion {sigma}_V_=1330km/s as measured from 57 cluster galaxies. It has regular X-ray emission without signs of substructure, a Gaussian velocity distribution, lack of a cooling flow region and significant deviations from the observed scaling laws between luminosity, temperature and velocity dispersion, indicating a possible merging shock. There is only one spectroscopically confirmed cluster radio galaxy, which is close to the X-ray peak. 1RXS J131423.6-251521 (for short RXJ1314-25) has z=0.2474 and {sigma}_V_=1100km/s from 37 galaxies. There are two distinct galaxy groups with a projected separation of ~700kpc. The velocity histogram is bi-modal with a redshift-space separation of ~1700km/s, and the X-ray emission is double peaked. Although there are no spectroscopically confirmed cluster radio galaxies, we have identified a plausible relic source candidate.
