- ID:
- ivo://CDS.VizieR/J/ApJ/766/37
- Title:
- Sizes of MRC radio galaxies and QSOs
- Short Name:
- J/ApJ/766/37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the currently popular orientation-based unified scheme, a radio galaxy appears as a quasar when its principal radio-axis happens to be oriented within a certain cone opening angle around the observer's line of sight. Due to geometrical projection, the observed sizes of quasars should therefore appear smaller than those of radio galaxies. We show that this simple, unambiguous prediction of the unified scheme is not borne out by the actually observed angular sizes of radio galaxies and quasars. Except in the original 3CR sample, based on which the unified scheme was proposed, in other much larger samples no statistically significant difference is apparent in the size distributions of radio galaxies and quasars. The population of low-excitation radio galaxies with apparently no hidden quasars inside, which might explain the observed excess number of radio galaxies at low redshifts, cannot account for the absence of any foreshortening of the sizes of quasars at large redshifts. On the other hand, from infrared and X-ray studies, there is evidence of a hidden quasar within a dusty torus in many radio galaxies, at z>0.5. It is difficult to reconcile this with the absence of foreshortening of quasar sizes at even these redshifts, and perhaps one has to allow that the major radio axis may not have anything to do with the optical axis of the torus. Otherwise, to resolve the dichotomy of radio galaxies and quasars, a scheme quite different from the present might be required.
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282. SN 1987A 3mm image
- ID:
- ivo://CDS.VizieR/J/A+A/541/L2
- Title:
- SN 1987A 3mm image
- Short Name:
- J/A+A/541/L2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The proximity of core-collapse supernova 1987A (SN 1987A) in the Large Magellanic Cloud (LMC) and its rapid evolution make it a unique case study of the development of a young supernova remnant. We aim at resolving the remnant of SN 1987A for the first time in the 3-mm band (at 94GHz).
- ID:
- ivo://CDS.VizieR/J/A+A/642/A136
- Title:
- Sources detected at 325 and 610 MHz in Cygnus
- Short Name:
- J/A+A/642/A136
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observations at the radio continuum band below the gigahertz band are key when the nature and properties of non-thermal sources are investigated because their radio radiation is strongest at these frequencies. The low radio frequency range is therefore the best to spot possible counterparts to very high-energy (VHE) sources: relativistic particles of the same population are likely to be involved in radio and high-energy radiation processes. Some of these counterparts to VHE sources can be stellar sources. The Cygnus region in the northern sky is one of the richest in this type of sources that are potential counterparts to VHEsources. We surveyed the central ~15 sq deg of the Cygnus constellation at the 325 and 610MHz bands with angular resolutions and sensitivities of 10" and 6", and 0.5 and 0.2mJy/beam, respectively. The data were collected during 172 hours in 2013-2017, using the Giant Metrewave Radio Telescope (GMRT) with 32MHz bandwidth, and were calibrated using the SPAM routines. The source extraction was carried out with the PyBDSF tool,followed by verification through visual inspection of every putative catalog candidate source in order to determine its reliability. In this first paper we present the catalog of sources, consisting of 1048 sources at 325MHz and 2796 sources at 610MHz. By cross-matching the sources from both frequencies with the objects of the SIMBAD database, we found possible counterparts for 143 of them. Most of the sources from the 325MHz catalog (993) were detected at the 610MHz band, and their spectral index alpha was computed adopting S(nu){prop.to}nu^alpha^. The maximum of the spectral index distribution is at alpha=-1, which is characteristic of non-thermal emitters and might indicate an extragalactic population.
- ID:
- ivo://CDS.VizieR/VIII/74A
- Title:
- SPECFIND Catalog of radio continuum spectra
- Short Name:
- VIII/74A
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- SPECFIND is a new tool to extract cross-identifications and radio continuum spectra from radio catalogues contained in the VIZIER database of the CDS. It is designed to handle radio surveys of very different resolutions and sensitivities. Power laws are fitted to the radio spectra, resulting in the determination of a power law slope and a zero-point. SPECFIND has been applied to 22 survey catalogues at 11 different frequencies (159 - 8400 MHz) containing a total of 3.5 million sources, leading to 757894 independent radio cross-identifications and 66866 independent radio spectra with more than two independent frequencies. The code was tested and its results validated by a comparison between the spectral indices found by SPECFIND and those determined by other authors. The determined spectral indices have an error of about +/-0.3. Negative spectral indices have smaller errors, while the error of positive spectral indices can be larger, mainly because of the occurrence of a peak in the spectrum. The code is quite rapid (less than 3 hr running time on a standard PC for 3.5 million sources) and since it is written in C, it can be run on virtually all PCs with at least 512~MB RAM. It produces an output of variable format that can be adapted easily to the purpose of the user. The results of the spectrum identification process are provided as a master table, where a spectrum is attached to each radio source. Due to the SPECFIND algorithm, different radio components of the same physical source can have somewhat different slopes and zero-points. The SPECFIND subdirectory contains the code (in C) and the data used to generate the catalogue, as well as a user manual (manual.ps). For compilation please IMPERATIVELY read the README file stored in the SPECFIND subdirectory.
- ID:
- ivo://CDS.VizieR/VIII/85A
- Title:
- SPECFIND V2.0 Catalog of radio continuum spectra
- Short Name:
- VIII/85A
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the second release of the SPECFIND catalogue. For the radio cross-identification we included 3.76 million sources from 105 VizieR radio catalogues. The SPECFIND V2.0 catalogue contains about 107000 physical objects with associated radio spectra. With an increase of 8% of available sources with respect to the first release, we could increase the number of radio objects by 60%. The results of the spectrum identification process are provided as a master table, where a spectrum is attached to each radio source. Due to the SPECFIND algorithm, different radio sources of the same physical object can have somewhat different slopes and zero-points. We also present radio sources from positional cross-identification only taking into account the source extent and the survey resolution (overlapping beams or extents). The source flux densities were not taken into account as it was done for the SPECFINDV2.0 catalogue. In this sense, it represents the waste basket of SPECFINDV2.0.
- ID:
- ivo://CDS.VizieR/VIII/104
- Title:
- SPECFIND V3.0 Catalog of radio continuum spectra
- Short Name:
- VIII/104
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Many radio continuum catalogs with different sensitivity limits and spatial resolutions are published via the VizieR database. Because of the diversity of spatial resolution, the cross-identification of individual sources is complex. By assuming a power-law spectrum, the SPECFIND tool is able to handle radio surveys at different frequencies from different instruments and different resolutions. Since the former version of the SPECFIND catalog was released ten years ago, hundreds of new radio continuum catalogs have been published. We upgraded the SPECFIND tool to reach a wider frequency range, especially the lower-frequency radio regime, as well as to have better spatial sky coverage. We adapted special selection criteria to all radio tables listed in VizieR to define a final sample of new catalogs. We implemented the new catalogs into the SPECFIND tool by unifying them and then compare the results to the last version. Furthermore we present and investigate sources with spectral breaks around 1.4GHz and around 325MHz. By increasing the number of implemented SPECFIND catalogs from 115 to 204, we improve the number of resulting spectra from 107500 to 340000 and increase the number of cross-identified sources from 600000 to 1.6 million. Furthermore, we present two samples of spectral break sources. The first sample includes 3104 spectral break sources with turnover frequencies around 1.4GHz, the second sample includes 18075 spectral break sources with turnover frequencies around 325MHz. Both samples include concave sources and Gigaherz-Peaked Spectrum (GPS) or Megaherz-Peaked Spectrum (MPS) sources. The SPECFIND V3.0 catalog is a very useful resource and a powerful open access tool, reachable via VizieR. By tripling the resulting spectra and including many radio continuum surveys from the last 50 years, we provide a significantly extended catalog of cross-identified radio continuum sources. Furthermore, the SIMBAD database will be updated using the SPECFIND V3.0 catalog and will contain more radio continuum data, serving the needs of future projects.
- ID:
- ivo://CDS.VizieR/J/MNRAS/473/4436
- Title:
- Spectral properties of 441 radio pulsars
- Short Name:
- J/MNRAS/473/4436
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the spectral properties of 441 pulsars observed with the Parkes radio telescope near the centre frequencies of 728, 1382 and 3100MHz. The observations at 728 and 3100MHz were conducted simultaneously using the dual-band 10-50cm receiver. These high-sensitivity, multifrequency observations provide a systematic and uniform sample of pulsar flux densities. We combine our measurements with spectral data from the literature in order to derive the spectral properties of these pulsars. Using techniques from robust regression and information theory, we classify the observed spectra in an objective, robust and unbiased way into five morphological classes: simple or broken power law, power law with either low- or high-frequency cut-off and log-parabolic spectrum. While about 79 per cent of the pulsars that could be classified have simple power-law spectra, we find significant deviations in 73 pulsars, 35 of which have curved spectra, 25 with a spectral break and 10 with a low-frequency turn-over. We identify 11 gigahertz-peaked spectrum (GPS) pulsars, with 3 newly identified in this work and 8 confirmations of known GPS pulsars; 3 others show tentative evidence of GPS, but require further low-frequency measurements to support this classification. The weighted mean spectral index of all pulsars with simple power-law spectra is -1.60+/-0.03. The observed spectral indices are well described by a shifted log-normal distribution. The strongest correlations of spectral index are with spin-down luminosity, magnetic field at the light-cylinder and spin-down rate. We also investigate the physical origin of the observed spectral features and determine emission altitudes for three pulsars.
- ID:
- ivo://CDS.VizieR/J/ApJS/174/313
- Title:
- Spectra of 388 bright 74MHz sources
- Short Name:
- J/ApJS/174/313
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As a service to the community, we have compiled radio frequency spectra from the literature for all sources within the VLA Low Frequency Sky Survey (VLSS) that are brighter than 15Jy at 74MHz. Over 160 references were used to maximize the amount of spectral data used in the compilation of the spectra, while also taking care to determine the corrections needed to put the flux densities from all reference on the same absolute flux density scale. With the new VLSS data, we are able to vastly improve on previous efforts to compile spectra of bright radio sources to frequencies below 100MHz because (1) the VLSS flux densities are more reliable than those from some previous low-frequency surveys and (2) the VLSS covers a much larger area of the sky ({delta}>-30{deg}) than many other low-frequency surveys (e.g., the 8C survey).
- ID:
- ivo://CDS.VizieR/J/AJ/124/2453
- Title:
- Spectroscopy of active galaxies in nearby clusters
- Short Name:
- J/AJ/124/2453
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used optical spectroscopy to investigate the active galaxy populations in a sample of 20 nearby Abell clusters. The targets were identified on the basis of 1.4GHz radio emission, which identifies them as either active galactic nuclei (AGNs) or galaxies forming stars at rates comparable to or greater than that of the Milky Way. The spectra were used to characterize the galaxies via their emission and absorption features.
- ID:
- ivo://CDS.VizieR/J/MNRAS/467/L31
- Title:
- SS Cyg rapid radio flaring in 2016
- Short Name:
- J/MNRAS/467/L31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The connection between accretion and jet production in accreting white dwarf binary systems, especially dwarf novae, is not well understood. Radio wavelengths provide key insights into the mechanisms responsible for accelerating electrons, including jets and outflows. Here, we present densely sampled radio coverage, obtained with the Arcminute MicroKelvin Imager Large Array, of the dwarf nova SS Cyg during its 2016 February anomalous outburst. The outburst displayed a slower rise (3d/mag) in the optical than typical ones and lasted for more than three weeks. Rapid radio flaring on time-scales <1h was seen throughout the outburst. The most intriguing behaviour in the radio was towards the end of the outburst where a fast, luminous ('giant'), flare peaking at ~20mJy and lasting for 15min was observed. This is the first time that such a flare has been observed in SS Cyg and insufficient coverage could explain its non-detection in previous outbursts. These data, together with past radio observations, are consistent with synchrotron emission from plasma ejection events as being the origin of the radio flares. However, the production of the giant flare during the declining accretion rate phase remains unexplained within the standard accretion-jet framework and appears to be markedly different to similar patterns of behaviour in X-ray binaries.
