- ID:
- ivo://CDS.VizieR/J/ApJ/893/68
- Title:
- RadioAstron. III. S5 0716+71 at uarcsec res.
- Short Name:
- J/ApJ/893/68
- Date:
- 03 Dec 2021 00:43:28
- Publisher:
- CDS
- Description:
- We present RadioAstron Space VLBI imaging observations of the BL Lac object S5 0716+71 made on 2015 January 3-4 at a frequency of 22GHz (wavelength {lambda}=1.3cm). The observations were made in the framework of the AGN Polarization Key Science Program. The source was detected on projected space-ground baselines up to 70833km (5.6 Earth diameters) for both parallel-hand and cross-hand interferometric visibilities. We have used these detections to obtain a full-polarimetric image of the blazar at an unprecedented angular resolution of 24{mu}as, the highest for this source to date. This enabled us to estimate the size of the radio core to be <12x5{mu}as and to reveal a complex structure and a significant curvature of the blazar jet in the inner 100{mu}as, which is an indication that the jet viewing angle lies inside the opening angle of the jet conical outflow. Fairly highly (15%) linearly polarized emission is detected in a jet region 19{mu}as in size, located 58{mu}as downstream from the core. The highest brightness temperature in the source frame is estimated to be >2.2x10^13^K for the blazar core. This implies that the inverse-Compton limit must be violated in the rest frame of the source, even for the largest Doppler factor {delta}~25 reported for 0716+714.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/623/A105
- Title:
- Radio catalogue of Galactic HII regions
- Short Name:
- J/A+A/623/A105
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Large-scale radio continuum surveys provide data to get insights into the physical properties of radio sources. HII regions are prominent radio sources produced by thermal emission of ionised gas around young massive stars. We identify and analyse HII regions in the Sino-German {lambda}6cm polarisation survey of the Galactic plane. Objects with flat radio continuum spectra together with infrared and/or H{alpha} emission were identified to be HII regions. For HII regions with small apparent sizes, we cross-matched the {lambda}6cm small-diameter source catalogue with the radio HII region catalogue compiled by Paladini and the infrared HII region catalogue based on the WISE data. Effelsberg {lambda}21cm and {lambda}11cm continuum survey data were used to determine source spectra. High angular resolution data from the Canadian Galactic Plane Survey and the NVSS were used to solve the confusion when low angular resolution observations are not sufficient. Extended HII regions were identified by overlaying the Paladini and the WISE HII regions onto the {lambda}6cm survey images for coincidences by eye. The TT-plot method was employed for spectral index verification. 401 HII regions were identified and their flux densities were determined with the Sino-German {lambda}6cm survey data. In the surveyed area, 76 pairs of sources are found to be duplicated in the Paladini HII region catalogue mainly due to the non-distinction of previous observations with different angular resolutions, and 78 objects in their catalogue are misclassified as HII regions, being actually planetary nebulae, supernova remnants or extragalactic sources that have steep spectra. More than 30 HII regions and HII region candidates from our {lambda}6cm survey data, especially extended ones, do not have counterparts in the WISE HII region catalogue, among which 9 are identified for the first time. Our results imply that some more Galactic HII regions still await to be discovered and the combination of multi-domain observations is important for HII region identification. Based on the newly derived radio continuum spectra and the evidence of infrared emission, the previously identified SNRs G11.1-1.0, G20.4+0.1 and G16.4-0.5 are believed to be HII regions.
- ID:
- ivo://CDS.VizieR/J/A+A/592/A94
- Title:
- Radio continuum and gas reservoir in NGC 3998
- Short Name:
- J/A+A/592/A94
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the nearby lenticular galaxy NGC 3998. This galaxy is known to host a low-power radio AGN with a kpc-size one-sided jet and a large, nearly polar HI disc. It is therefore a good system to study to understand the relation between the availability of cold-gas and the triggering of AGNs in galaxies. Our new WSRT data reveal two faint, S-shaped radio lobes extending out to ~10 kpc from the galaxy centre. Remarkably, we find that the inner HI disc warps back towards the stellar mid-plane in a way that mirrors the warping of the radio lobes. We suggest that the polar HI disc was accreted through a minor merger, and that the torques causing it to warp in the inner regions are also responsible for feeding the AGN. The "S" shape of the radio lobes would then be due to the radio jets adapting to the changing angular momentum of the accreted gas. The extended radio jets are likely poorly collimated, which would explain their quick fading and, therefore, their rarity in galaxies similar to NGC 3998. The fuelling of the central super-massive black hole is likely occurring via "discrete events", suggested by the observed variability of the radio core and the extremely high core dominance, which we attribute to the formation and ejection of a new jet resulting from a recent fuelling event.
- ID:
- ivo://CDS.VizieR/J/MNRAS/246/169
- Title:
- Radio continuum around G 73.9+0.9
- Short Name:
- J/MNRAS/246/169
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A field centered on the galactic supernova remnant (SNR) G073.9+00.9 was mapped in the continuum at 408 and 1420 MHz with the Dominion Radio Astrophysical Observatory (DRAO). The interferometer observations, of resolution 3.4x5.8 arcmin^2^ and 1.0x1.7 arcmin^2^ respectively, were complemented with single-dish data so that the resulting maps are sensitive to all structures down to the synthesized beam. Note that this list is part of the DRAO Penticton P-survey Database (Catalog <VIII/55>)
- ID:
- ivo://CDS.VizieR/II/199A
- Title:
- Radio continuum emission from stars
- Short Name:
- II/199A
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Radio data (1) Frequency in MHz (2) Maximun flux density in mJy (3) Minimun flux density in mJy. if =0, only one observation was made or the emission was steady (4) Code number of the reference (5) Remarks pertaining to the individual observations
- ID:
- ivo://CDS.VizieR/J/A+A/241/551
- Title:
- Radio continuum in Cygnus X region
- Short Name:
- J/A+A/241/551
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Cygnus X region has been observed at 408 and 1420 MHz with the Dominion Radio Astrophysical Observatory (DRAO), with an angular resolution of 3.5x5.2 and 1.0x1.5 arcmin.
- ID:
- ivo://CDS.VizieR/J/A+AS/111/311
- Title:
- Radio continuum study of the MC
- Short Name:
- J/A+AS/111/311
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- From observations with the Parkes radio telescope, we present catalogues of radio sources in the Large Magellanic Cloud at four frequencies: 1.40, 2.45, 4.75 and 8.55GHz, and an additional catalogue from a source analysis of the Parkes-MIT-NRAO survey at 4.85GHz. A total of 469 sources have been detected at least one of these frequencies, 132 of which are reported here for the first time as radio sources.
- ID:
- ivo://CDS.VizieR/J/A+AS/127/119
- Title:
- Radio continuum study of the MC
- Short Name:
- J/A+AS/127/119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- By comparing Parkes telescope radio surveys with the X-ray ROSAT All-Sky Survey (RASS) we have found 71 discrete sources of both radio and X-ray emission in the Large Magellanic Cloud (LMC). These 71 sources are mainly supernova remnants (SNRs) and SNR candidates (36), and background sources (27). For six of the sources we have no proposed identification and the other two are HII regions. A source-intensity comparison of the radio and X-ray sources shows very little correlation, but we note that the strongest SNRs at both radio and X-ray frequencies are young SNRs from Population I. Six new LMC SNR candidates are proposed. From the radio flux density of the SNRs we have estimated the SNR birth rate to be one every 100 (+/-20) yr and the star-formation rate (SFR) to be 0.7 (+/-0.2)M_{sun}_/yr. A similar comparison was undertaken for the Small Magellanic Cloud (SMC), but instead of the RASS we used a roster of pointed observations made with the ROSAT Position Sensitive Proportional Counter (PSPC). This comparison resulted in 27 sources in common between the Parkes radio and ROSAT PSPC surveys. Two new SMC sources are proposed for SNR candidates. The SMC SNR birth rate was estimated to be one every 350 (+/-70)yr and the SFR was estimated to be 0.15 (+/-0.05)M_{sun}_/yr.
- ID:
- ivo://CDS.VizieR/J/A+AS/120/77
- Title:
- Radio continuum study of the MC
- Short Name:
- J/A+AS/120/77
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new catalogue of radio sources in the Large Magellanic Cloud (LMC) based on observations at 2.30GHz with the Parkes radio telescope. A total of 119 sources have been detected. We compare positions and flux densities of these sources with previously published radio results and find no significant positional displacement or flux discrepancies.
- ID:
- ivo://CDS.VizieR/J/A+AS/130/421
- Title:
- Radio continuum study of the MC
- Short Name:
- J/A+AS/130/421
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of discrete radio sources in the Magellanic Clouds (MCs) using the latest large-scale radio surveys made with the Parkes radio telescope between 1.4 and 8.55GHz. These surveys achieved higher sensitivity than previous surveys done with the Parkes telescope and so the number of discrete radio sources detected towards the MCs has increased by factor of five. Also, we have obtained improved positions, flux densities and radio spectral indices for all of these sources. A total of 483 sources towards the Large Magellanic Cloud (LMC) and 224 towards the Small Magellanic Cloud (SMC) have been detected at at least one radio frequency. Most of the MC's sources have been classified in one of three groups: SNRs, HII regions or background sources according to classification criteria established here. In total, 209 discrete radio sources in the LMC and the 37 sources in the SMC are classified here to be either HII regions or SNRs. We investigate their luminosity functions as well as the statistics of background sources behind the MCs. Also, we examine the distribution of SNRs and HII regions in the MCs.
