- 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.
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- 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/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/575/A9
- Title:
- M17-SW datacubes in C and CO lines
- Short Name:
- J/A+A/575/A9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We probe the column densities and masses traced by the ionized [CII] and neutral [CI] atomic carbon with spectrally resolved maps, and compare them to the diffuse and dense molecular gas traced by [CI] and low-J CO lines toward the star-forming region M17 SW. We mapped a 4.1pcx4.7pc region in the [CI] 609{mu}m line using the APEX telescope, as well as the CO isotopologues with the IRAM 30m telescope. Data are analyzed based on velocity channel maps that are 1km/s wide. We correlate their spatial distribution with that of the [CII] map obtained with SOFIA/GREAT. Optically thin approximations were used to estimate the column densities of [CI] and [CII] in each velocity channel.
- ID:
- ivo://CDS.VizieR/J/A+A/592/A123
- Title:
- M51 total intensity image at 333MHz
- Short Name:
- J/A+A/592/A123
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Cosmic ray electrons (CREs) are a crucial part of the ISM and are observed via synchrotron emission. While much modelling has been carried out on the CRE distribution and propagation of the Milky Way, little has been done on normal external star-forming galaxies. Recent spectral data from a new generation of radio telescopes enable us to find more robust estimations of the CRE propagation To model the synchrotron spectral index of M51 using the diffusion energy-loss equation and to compare the model results with the observed spectral index determined from recent low-frequency observations with LOFAR. We solve the time-dependent diffusion energy-loss equation for CREs in M51. This is the first time that this model for CRE propagation has been solved for a realistic distribution of CRE sources, which we derive from the observed star formation rate, in an external galaxy. The radial variation of the synchrotron spectral index and scale-length produced by the model are compared to recent LOFAR and older VLA observational data and also to new observations of M51 at 325MHz obtained with the GMRT. We find that propagation of CREs by diffusion alone is sufficient to reproduce the observed spectral index distribution in M51. An isotropic diffusion coefficient with a value of 6.6+/-0.2Dunits is found to fit best and is similar to what is seen in the Milky Way. We estimate an escape time of 11Myr from the central galaxy to 88Myr in the extended disk. It is found that an energy dependence of the diffusion coefficient is not important for CRE energies in the range 0.01GeV-3GeV. We are able to reproduce the dependence of the observed synchrotron scale-lengths on frequency, with l{propto}{nu}^-1/4^ in the outer disk and l{propto}{nu}^-1/8^ in the inner disk.
- ID:
- ivo://CDS.VizieR/J/ApJ/853/68
- Title:
- Multi-epoch VLBA imaging of 20 Tev blazars
- Short Name:
- J/ApJ/853/68
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 88 multi-epoch Very Long Baseline Array (VLBA) images (most at an observing frequency of 8GHz) of 20TeV blazars, all of the high-frequency-peaked BL Lac (HBL) class, that have not been previously studied at multiple epochs on the parsec scale. From these 20 sources, we analyze the apparent speeds of 43 jet components that are all detected at four or more epochs. As has been found for other TeV HBLs, the apparent speeds of these components are relatively slow. About two-thirds of the components have an apparent speed that is consistent (within 2{sigma}) with no motion, and some of these components may be stationary patterns whose apparent speed does not relate to the underlying bulk flow speed. In addition, a superluminal tail to the apparent speed distribution of the TeV HBLs is detected for the first time, with eight components in seven sources having a 2{sigma} lower limit on the apparent speed exceeding 1c. We combine the data from these 20 sources with an additional 18 sources from the literature to analyze the complete apparent speed distribution of all 38 TeV HBLs that have been studied with very long baseline interferometry at multiple epochs. The highest 2{sigma} apparent speed lower limit considering all sources is 3.6c. This suggests that bulk Lorentz factors of up to about 4, but probably not much higher, exist in the parsec-scale radio-emitting regions of these sources, consistent with estimates obtained in the radio by other means such as brightness temperatures. This can be reconciled with the high Lorentz factors estimated from the high-energy data if the jet has velocity structures consisting of different emission regions with different Lorentz factors. In particular, we analyze the current apparent speed data for the TeV HBLs in the context of a model with a fast central spine and a slower outer layer.
- 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.
