- 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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Search Results
- 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/ApJS/107/19
- Title:
- MRC/1Jy Radio source survey. I.
- Short Name:
- J/ApJS/107/19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the first in a series of papers discussing the properties of a complete set of radio sources selected near S408=1Jy. We present optical or infrared identifications for a sample of 452 radio galaxies. The sources were selected from the 408MHz Molonglo Reference Catalog, restricted only by flux density and position on the sky, as follows: S408>0.95Jy and -30<decl.(1950)<-20, and 9h20m<R.A.(1950)<14h4m or 20h20m<R.A.(1950)<6h14m. This complete sample, the MRC/1 Jy survey, contains 558 radio galaxies or quasars, of which six are occulted by bright stars or galaxies and two are multiple confused sources. Of the remaining 550 sources, 527, or 96%, are identified to an r magnitude of 25, and eight additional sources are identified to K=19. Of the 17 unocculted objects that remain unidentified, 15 are sources for which we have either poor radio maps or inadequate optical/IR images. This paper presents finding charts and astrometric positions for the 452 sources that are not identified as either quasars or BL Lacertae objects. Magnitudes in the r passband accurate to typically 0.1mag are given for 353 of the radio galaxy identifications. Redshifts for 268 of the galaxies are also listed; these have been derived from 450 spectroscopic observations. The radio observations, quasar and BL Lac identifications, spectroscopy, and near-IR images will be presented in subsequent papers in this series.
- ID:
- ivo://CDS.VizieR/J/MNRAS/381/341
- Title:
- MRCR-SUMSS Ultra-steep-spectrum (USS) sample
- Short Name:
- J/MNRAS/381/341
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper introduces a new program to find high-redshift radio galaxies in the Southern hemisphere through ultra-steep spectrum (USS) selection. We define a sample of 234 USS radio sources with spectral indices {alpha}^843^_408_<=-1.0 (S_{nu}_{prop.to}{nu}^alpha^) and flux densities S_408_>=200mJy in a region of 0.35sr, chosen by cross-correlating the revised 408MHz Molonglo Reference Catalogue, the 843MHz Sydney University Molonglo Sky Survey and the 1400MHz NRAO VLA Sky Survey in the overlap region -40{deg}<DE<-30{deg}. We present Australia Telescope Compact Array (ATCA) high-resolution 1384 and 2368MHz radio data for each source, which we use to analyse the morphological, spectral index and polarization properties of our sample. We find that 85 per cent of the sources have observed-frame spectral energy distributions that are straight over the frequency range 408-2368MHz, and that, on average, sources with smaller angular sizes have slightly steeper spectral indices and lower fractional linear polarization. Fractional polarization is anticorrelated with flux density at both 1400 and 2368MHz. We also use the ATCA data to determine observed-frame Faraday rotation measures for half of the sample.
- ID:
- ivo://CDS.VizieR/J/A+A/633/A163
- Title:
- Mrk 231 CO(1-0) and CN(1-0) line observations
- Short Name:
- J/A+A/633/A163
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present interferometric observations of the CN(1-0) line emission in Mrk 231 and combine them with previous observations of CO and other H_2_ gas tracers to study the physical properties of the massive molecular outflow. We find a strong boost of the CN/CO(1-0) line luminosity ratio in the outflow of Mrk 231, which is unprecedented compared to any other known Galactic or extragalactic astronomical source. For the dense gas phase in the outflow traced by the HCN and CN emissions, we infer X_CN_=[CN]/[H_2_]>X_HCN_ by at least a factor of three, with H_2_ gas densities of n_H2_~10^5-6^cm^-3^. In addition, we resolve for the first time narrow spectral features in the HCN(1-0) and HCO^+^(1-0) high-velocity line wings tracing the dense phase of the outflow. The velocity dispersions of these spectral features, {sigma}_v_~7-20km/s, are consistent with those of massive extragalactic giant molecular clouds detected in nearby starburst nuclei. The H_2_ gas masses inferred from the HCN data are quite high, M_mol_~0.3-5x10^8^M_{sun}_. Our results suggest that massive complexes of denser molecular gas survive embedded into the more diffuse H_2_ phase of the outflow, and that the chemistry of these outflowing dense clouds is strongly aected by UV radiation.
- ID:
- ivo://CDS.VizieR/J/MNRAS/426/416
- Title:
- Mrk 6 H{alpha}, H{beta} and H{gamma} spectra
- Short Name:
- J/MNRAS/426/416
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of optical spectral and photometric observations of the nucleus of Markarian 6 made with the 2.6-m Shajn telescope at the Crimean Astrophysical Observatory. The continuum and emission Balmer-line intensities varied by more than a factor of two during 1992-2008. The lag between the continuum and H{beta} emission-line flux variations is 21.1+/-1.9days. For the H{alpha} line the lag is about 27-days, but its uncertainty is much larger.
2397. Mrk421 in March 2010
- ID:
- ivo://CDS.VizieR/J/A+A/578/A22
- Title:
- Mrk421 in March 2010
- Short Name:
- J/A+A/578/A22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A flare from the TeV blazar Mrk 421, occurring in March 2010, was observed for 13 consecutive days from radio to very high energy (VHE; E>100GeV) gamma-rays with MAGIC, VERITAS, Whipple, FermiLAT, MAXI, RXTE, Swift, GASP-WEBT, and several optical and radio telescopes. We model the day-scale SEDs with one-zone and two-zone synchrotron self-Compton (SSC) models, investigate the physical parameters, and evaluate whether the observed broadband SED variability can be associated to variations in the relativistic particle population. Flux variability was remarkable in the X-ray and VHE bands while it was minor or not significant in the other bands. The one-zone SSC model can describe reasonably well the SED of each day for the 13 consecutive days. This flaring activity is also very well described by a two-zone SSC model, where one zone is responsible for the quiescent emission while the other smaller zone, which is spatially separated from the first one, contributes to the daily-variable emission occurring in X-rays and VHE gamma-rays. Both the one-zone SSC and the two-zone SSC models can describe the daily SEDs via the variation of only four or five model parameters, under the hypothesis that the variability is associated mostly to the underlying particle population. This shows that the particle acceleration and cooling mechanism producing the radiating particles could be the main one responsible for the broadband SED variations during the flaring episodes in blazars. The two-zone SSC model provides a better agreement to the observed SED at the narrow peaks of the low- and high-energy bumps during the highest activity, although the reported one-zone SSC model could be further improved by the variation of the parameters related to the emitting region itself ({delta}, B and R), in addition to the parameters related to the particle population.
- 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/561/A64
- Title:
- Mrk 996 optical spectroscopy
- Short Name:
- J/A+A/561/A64
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an integral field spectroscopic study with the Gemini Multi-Object Spectrograph (GMOS) of the unusual blue compact dwarf (BCD) galaxy Mrk 996. We show through velocity and dispersion maps, emission-line intensity and ratio maps, and by a new technique of electron density limit imaging that the ionization properties of different regions in Mrk 996 are correlated with their kinematic properties.
- ID:
- ivo://CDS.VizieR/J/A+A/437/87
- Title:
- Mrk 335 photometry in 1995-2004
- Short Name:
- J/A+A/437/87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of UBVRI photometry of Mrk 335 in 1995-2004. This object has a large amplitude of variability, reaching about 1.1, 0.9, 0.7mag in the U,B,V and 0.3mag in the Rc, Ic bands, respectively. ************************************************************************** * * * Sorry, but the author(s) never supplied the tabular material * * announced in the paper * * * **************************************************************************
