- ID:
- ivo://CDS.VizieR/J/MNRAS/347/837
- Title:
- Radio and K-band obs. of Ultra-Steep sources
- Short Name:
- J/MNRAS/347/837
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A sample of 76 ultra-steep spectrum (USS) radio sources is defined from the 843-MHz Sydney University Molonglo Sky Survey (SUMSS) and 1.4-GHz NRAO VLA Sky Survey (NVSS) radio surveys with spectral index {alpha}<-1.3 and S(1.4GHz)>15mJy; 71 of these sources without bright optical or near-infrared counterparts at 1.385GHz were observed with the Australia Telescope Compact Array (ATCA), providing 5arcsec resolution images and subarcsec positional accuracy. To identify their host galaxies, near-infrared K-band images were obtained with IRIS2 at the AAT and SofI at the NTT; 92% of the USS sources could be identified down to K~20.5. 142 FITS files containing the radio maps and the K-band images are included in the fits subdirectory.
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Search Results
- 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/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/AJ/152/82
- Title:
- Radio continuum survey of Kepler K2 mission Field 1
- Short Name:
- J/AJ/152/82
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first dedicated radio continuum survey of a Kepler K2 mission field, Field 1, covering the North Galactic Cap. The survey is wide field, contemporaneous, multi-epoch, and multi-resolution in nature and was conducted at low radio frequencies between 140 and 200MHz. The multi-epoch and ultra wide field (but relatively low resolution) part of the survey was provided by 15 nights of observation using the Murchison Widefield Array (MWA) over a period of approximately a month, contemporaneous with K2 observations of the field. The multi-resolution aspect of the survey was provided by the low resolution (4') MWA imaging, complemented by non-contemporaneous but much higher resolution (20'') observations using the Giant Metrewave Radio Telescope (GMRT). The survey is, therefore, sensitive to the details of radio structures across a wide range of angular scales. Consistent with other recent low radio frequency surveys, no significant radio transients or variables were detected in the survey. The resulting source catalogs consist of 1085 and 1468 detections in the two MWA observation bands (centered at 154 and 185MHz, respectively) and 7445 detections in the GMRT observation band (centered at 148MHz), over 314 square degrees. The survey is presented as a significant resource for multi-wavelength investigations of the more than 21000 target objects in the K2 field. We briefly examine our survey data against K2 target lists for dwarf star types (stellar types M and L) that have been known to produce radio flares.
- ID:
- ivo://CDS.VizieR/J/ApJ/768/37
- Title:
- Radio emission from SDSS quasars
- Short Name:
- J/ApJ/768/37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We used the 1.4GHz NVSS to study radio sources in two color-selected QSO samples: a volume-limited sample of 1313 QSOs defined by M_i_<-23 in the redshift range 0.2<z<0.45 and a magnitude-limited sample of 2471 QSOs with m_r_<=18.5 and 1.8<z<2.5. About 10% were detected above the 2.4mJy NVSS catalog limit and are powered primarily by active galactic nuclei (AGNs). The space density of the low-redshift QSOs evolves as {rho}{prop.to}(1+z)^6^. In both redshift ranges the flux-density distributions and luminosity functions of QSOs stronger than 2.4mJy are power laws, with no features to suggest more than one kind of radio source. Extrapolating the power laws to lower luminosities predicts the remaining QSOs should be extremely radio quiet, but they are not. Most were detected statistically on the NVSS images with median peak flux densities S_p_(mJy/beam){approx}0.3 and 0.05 in the low- and high-redshift samples, corresponding to spectral luminosities log [L_1.4GHz_(W/Hz)]{approx}22.7 and 24.1, respectively. We suggest that the faint radio sources are powered by star formation at rates dM/dt~20M_{sun}_/yr in the moderate luminosity (median <M_i_>{approx}-23.4) low-redshift QSOs and dM/dt~500M_{sun}_/yr in the very luminous (<M_i_>{approx}-27.5) high-redshift QSOs. Such luminous starbursts [<log(L_IR_/L_{sun}_)>~11.2 and 12.6, respectively] are consistent with "quasar mode" accretion in which cold gas flows fuel both AGN and starburst.
- ID:
- ivo://CDS.VizieR/J/A+A/552/A19
- Title:
- Radio-farIR correlation in NGC 6946
- Short Name:
- J/A+A/552/A19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We derive the distribution of the synchrotron spectral index across NGC 6946 and investigate the correlation between the radio continuum (synchrotron) and far-infrared (FIR) emission using the KINGFISH Herschel PACS and SPIRE data.
- ID:
- ivo://CDS.VizieR/J/A+A/650/A83
- Title:
- Radio flux densities of neutrino associations
- Short Name:
- J/A+A/650/A83
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Identifying the most likely sources for high-energy neutrino emission has been one of the main topics in high-energy astrophysics ever since the first observation of high-energy neutrinos by the IceCube Neutrino Observatory. Active galactic nuclei with relativistic jets, also known as blazars, have been considered to be one of the main candidates because of their ability to accelerate particles to high energies. We study the connection between radio emission and IceCube neutrino events using data from the Owens Valley Radio Observatory (OVRO) and Metsahovi Radio Observatory blazar monitoring programs. We identify sources in our radio monitoring sample that are positionally consistent with IceCube high-energy neutrino events. We estimate their mean flux density and variability amplitudes around the neutrino arrival time, and compare these with values from random samples to establish the significance of our results. We find radio source associations within our samples with 15 high-energy neutrino events detected by IceCube. Nearly half of the associated sources are not detected in the {gamma}-ray energies, but their radio variability properties and Doppler boosting factors are similar to the {gamma}-ray detected objects in our sample, meaning that they could still be potential neutrino emitters. We find that the number of strongly flaring objects in our statistically complete OVRO samples is unlikely to be a random coincidence (at 2{sigma} level). Based on our results, we conclude that although it is clear that not all neutrino events are associated with strong radio flaring blazars, observations of large-amplitude radio flares in a blazar at the same time as a neutrino event are unlikely to be a random coincidence.
- ID:
- ivo://CDS.VizieR/J/ApJ/838/139
- Title:
- Radio follow-up on 3FGL unassociated sources
- Short Name:
- J/ApJ/838/139
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The third Fermi Large Area Telescope {gamma}-ray source catalog (3FGL) contains over 1000 objects for which there is no known counterpart at other wavelengths. The physical origin of the {gamma}-ray emission from those objects is unknown. Such objects are commonly referred to as unassociated and mostly do not exhibit significant {gamma}-ray flux variability. We performed a survey of all unassociated {gamma}-ray sources found in 3FGL using the Australia Telescope Compact Array and Very Large Array in the range 4.0-10.0 GHz. We found 2097 radio candidates for association with {gamma}-ray sources. The follow-up with very long baseline interferometry for a subset of those candidates yielded 142 new associations with active galactic nuclei that are {gamma}-ray sources, provided alternative associations for seven objects, and improved positions for another 144 known associations to the milliarcsecond level of accuracy. In addition, for 245 unassociated {gamma}-ray sources we did not find a single compact radio source above 2 mJy within 3{sigma} of their {gamma}-ray localization. A significant fraction of these empty fields, 39%, are located away from the Galactic plane. We also found 36 extended radio sources that are candidates for association with a corresponding {gamma}-ray object, 19 of which are most likely supernova remnants or H II regions, whereas 17 could be radio galaxies.
