- 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.
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Search Results
- 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/ApJ/901/51
- Title:
- Radio continuum param. of Galactic HII regions
- Short Name:
- J/ApJ/901/51
- Date:
- 15 Feb 2022 14:31:45
- Publisher:
- CDS
- Description:
- Sgr E is a massive star formation complex found toward the Galactic center that consists of numerous discrete, compact HII regions. It is located at the intersection between the central molecular zone (CMZ) and the far dust lane of the Galactic bar, similar to "hot spots" seen in external galaxies. Compared with other Galactic star formation complexes, the Sgr E complex is unusual because its HII regions all have similar radio luminosities and angular extents, and they are deficient in ~10{mu}m emission from their photodissociation regions (PDRs). Our Green Bank Telescope radio recombination line observations increase the known membership of Sgr E to 19 HII regions. There are 43 additional HII region candidates in the direction of Sgr E, 26 of which are detected for the first time here using MeerKAT 1.28GHz data. Therefore, the true HII region population of Sgr E may number >60. Using APEX SEDIGISM ^13^CO 2->1 data we discover a 3.0x10^5^M_{sun}_ molecular cloud associated with Sgr E, but find few molecular or far-infrared concentrations at the locations of the Sgr E HII regions. Comparison with simulations and an analysis of its radio continuum properties indicate that Sgr E formed upstream in the far dust lane of the Galactic bar a few million years ago and will overshoot the CMZ, crashing into the near dust lane. We propose that the unusual infrared properties of the Sgr E HII regions are caused by their orbits about the Galactic center, which have possibly stripped their PDRs.
- ID:
- ivo://CDS.VizieR/J/MNRAS/507/2885
- Title:
- Radio continuum sources behind LMC
- Short Name:
- J/MNRAS/507/2885
- Date:
- 07 Feb 2022 08:00:21
- Publisher:
- CDS
- Description:
- We present a comprehensive multifrequency catalogue of radio sources behind the Large Magellanic Cloud (LMC) between 0.2 and 20GHz, gathered from a combination of new and legacy radio continuum surveys. This catalogue covers an area of ~144deg^2^ at angular resolutions from 45 arcsec to ~3 arcmin. We find 6434 discrete radio sources in total, of which 3789 are detected at two or more radio frequencies. We estimate the median spectral index ({alpha}; where S_v_~{nu}^{alpha}^) of {alpha}=-0.89 and mean of -0.88+/-0.48 for 3636 sources detected exclusively at two frequencies (0.843 and 1.384GHz) with similar resolution [full width at half-maximum (FWHM) ~40-45 arcsec]. The large frequency range of the surveys makes it an effective tool to investigate Gigahertz Peak Spectrum (GPS), Compact Steep Spectrum (CSS), and Infrared Faint Radio Source (IFRS) populations within our sample. We find 10 GPS candidates with peak frequencies near 5GHz, from which we estimate their linear size. 1866 sources from our catalogue are CSS candidates with {alpha}<-0.8. We found six candidates for High Frequency Peaker (HFP) sources, whose radio fluxes peak above 5GHz and no sources with unconstrained peaks and {alpha}>0.5. We found optical counterparts for 343 of the radio continuum sources, of which 128 have a redshift measurement. Finally, we investigate the population of 123 IFRSs found in this study.
- ID:
- ivo://CDS.VizieR/J/A+A/418/1
- Title:
- Radio continuum spectra in Virgo cluster region
- Short Name:
- J/A+A/418/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New radio continuum observations of galaxies in the Virgo cluster region at 4.85, 8.6, and 10.55GHz are presented. These observations are combined with existing measurements at 1.4 and 0.6GHz. The sample includes 81 galaxies where spectra with more than two frequencies could be derived. Galaxies that show a radio-FIR excess exhibit central activity (HII, LINER,AGN). The four Virgo galaxies with the highest absolute radio excess are found within 2 degrees of the center of the cluster. Galaxies showing flat radio spectra also host active centers. There is no clear trend between the spectral index and the galaxy's distance to the cluster center.
- 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/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.
