- ID:
- ivo://CDS.VizieR/VIII/65
- Title:
- 1.4GHz NRAO VLA Sky Survey (NVSS)
- Short Name:
- VIII/65
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The NRAO VLA Sky Survey (NVSS) is a radio continuum survey covering the sky north of -40{deg} declination at 1.4GHz. The principal data products of the NVSS are a set of 2326 4x4{deg} continuum "cubes" with three planes containing Stokes I, Q, and U images, plus a catalog of almost 2 million discrete sources stronger than a flux density of about 2.5mJy. The images all have 45 arcsecond FWHM angular resolution and nearly uniform sensitivity. Their rms brightness fluctuations are approximately 0.45mJy/beam=0.14K (Stokes I) and 0.29mJy/beam=0.09K (Stokes Q and U). The rms uncertainties in right ascension and declination vary from <= ~1arcsecond for the 400,000 sources stronger than 15mJy to 7arcseconds at the survey limit. A more detailed description is provided in the printed paper and at the NVSS website at http://www.cv.nrao.edu/nvss/ where all data products, user software, and updates were released as soon as they were produced and verified.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/559/A75
- Title:
- 43GHz observation of the blazar Mrk 421
- Short Name:
- J/A+A/559/A75
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results obtained for the AGN Markarian 421 by model-fitting the data in the visibility plane, studing the proper motion of jet components, the light curve, and the spectral index of the jet features. We compare the radio data with optical light curves obtained at the Steward Observatory, considering also the optical polarization information. Mrk 421 has a bright nucleus and a one-sided jet extending towards the north-west for a few parsecs. The model-fits show that brightness distribution is well described using 6-7 circular Gaussian components, four of which are reliably identified at all epochs; all components are effectively stationary except for component D, at ~0.4mas from the core, whose motion is however subluminal. The analysis of the light curve shows two different states, with the source being brighter and more variable in the first half of 2011 than in the second half. The highest flux density is reached in February. A comparison with the optical data reveals an increase of the V magnitude and of the fractional polarization simultaneous with the enhancement of the radio activity.
- ID:
- ivo://CDS.VizieR/J/ApJ/655/958
- Title:
- 90-GHz observations in NGC 1333
- Short Name:
- J/ApJ/655/958
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We observed the clustered star forming complex NGC 1333 with the BIMA and FCRAO telescopes in the transitions HCO+(1-0) and N_2_H+(1-0) over an area with resolution ~10" (0.015pc). The N_2_H+ emission follows very closely the submillimeter dust continuum emission, while HCO+ emission appears more spatially extended and also traces outflows. We have identified 93 N_2_H+ cores using the CLUMPFIND algorithm, and we derive N_2_H+ core masses between 0.05 and 2.5M_{sun}_ , with uncertainties of a factor of a few, dominated by the adopted N_2_H+ abundance.
- ID:
- ivo://CDS.VizieR/J/ApJS/51/67
- Title:
- 5 GHz Observations of Arecibo 611 MHz Sources
- Short Name:
- J/ApJS/51/67
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Arecibo 611 MHz survey of Durdin et al. (1975) listed 3118 radio sources stronger than 0.35 Jy in the region -3d to +19d and 22h to 13h. Of these sources, 2911 have been observed using the NRAO 300 foot transit telescope at 4755 MHz. Positions, fluxes, and spectral indices are given for the 2661 detected sources. The beamwidth of the 300 foot telescope is nominally 2.8 arcmin FWHM at 6 cm, compared to the 12 arcmin beamwidth of the Arecibo survey, allowing a significant improvement in source positions.
- ID:
- ivo://CDS.VizieR/J/AJ/133/1947
- Title:
- 37GHz observations of BL Lac objects
- Short Name:
- J/AJ/133/1947
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 37GHz data obtained at Metsahovi Radio Observatory in 2001 December-2005 April for a large sample of BL Lacertae objects. Metsahovi radio telescope is a radome enclosed antenna with a diameter of 13.7 metres. The 37 GHz receiver is a dual horn, Dicke-switched receiver with a HEMT preamplifier, and is operated at room temperature. The observations are ON-ON observations, alternating the source and the sky in each feed horn. A typical integration time to obtain one flux density data point is 1200-1600s, and the detection limit under optimal weather conditions is about 0.2Jy.
- ID:
- ivo://CDS.VizieR/J/ApJ/731/L41
- Title:
- 1.4GHz observations of bright early-type galaxies
- Short Name:
- J/ApJ/731/L41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have measured the radio continuum emission of 396 early-type galaxies brighter than K=9, using 1.4GHz imagery from the NRAO Very Large Array Sky Survey, Green Bank 300ft Telescope, and 64m Parkes Radio Telescope. For M_K_<-24 early-type galaxies, the distribution of radio powers at fixed absolute magnitude spans four orders of magnitude and the median radio power is proportional to K-band luminosity to the power 2.78+/-0.16. The measured flux densities of M_K_<-25.5 early-type galaxies are greater than zero in all cases. It is thus highly likely that the most massive galaxies always host an active galactic nucleus or have recently undergone star formation.
- ID:
- ivo://CDS.VizieR/J/MNRAS/430/1961
- Title:
- 93.2GHz observations of 9C sources
- Short Name:
- J/MNRAS/430/1961
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from follow-up observations of a sample of 80 radio sources, originally detected as part of the 15.2-GHz Ninth Cambridge (9C) survey. The observations were carried out, close to simultaneously, at two frequencies: 15.7GHz, using the Arcminute Microkelvin Imager (AMI) Large Array, and 93.2GHz, using the Combined Array for Research in Millimeter-wave Astronomy (CARMA). There is currently little direct information on the 90-GHz-band source count for S<~1Jy. However, we have used the measured 15.7-to-93.2-GHz spectral-index distribution and 9C source count to predict the differential source count at 93.2GHz as 26+/-4(S/Jy)^-2.15^Jy^-1^sr^-1^; our projection is estimated to be most accurate for 10<~S<~100mJy. Our estimated differential count is more than twice the 90-GHz prediction made by Waldram et al. (2007, Cat. J/MNRAS/379/1442); we believe that this discrepancy is because the measured 43-GHz flux densities used in making their prediction were too low. Similarly, our prediction is significantly higher than that of Sadler et al. (2008, Cat. J/MNRAS/385/1656) at 95GHz. Since our spectral-index distribution is similar to the 20-to-95-GHz distribution measured by Sadler et al. and used in making their prediction, we believe that the difference is almost entirely attributable to the dissimilarity in the lower frequency counts used in making the estimates.
- ID:
- ivo://CDS.VizieR/J/AJ/142/3
- Title:
- 1.4GHz observations of Stripe 82
- Short Name:
- J/AJ/142/3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a high-resolution radio survey of the Sloan Digital Sky Survey (SDSS) Southern Equatorial Stripe, a.k.a. Stripe 82. This 1.4GHz survey was conducted with the Very Large Array primarily in the A-configuration, with supplemental B-configuration data to increase sensitivity to extended structure. The survey has an angular resolution of 1.8" and achieves a median rms noise of 52{mu}Jy/beam over 92deg^2^. This is the deepest 1.4GHz survey to achieve this large of an area, filling a gap in the phase space between small, deep and large, shallow surveys. It also serves as a pilot project for a larger high-resolution survey with the Expanded Very Large Array. We discuss the technical design of the survey and details of the observations, and we outline our method for data reduction. We present a catalog of 17969 isolated radio components, for an overall source density of ~195sources/deg^2^. The astrometric accuracy of the data is excellent, with an internal check utilizing multiply observed sources yielding an rms scatter of 0.19" in both right ascension and declination. A comparison to the SDSS-DR7 Quasar Catalog further confirms that the astrometry is well tied to the optical reference frame, with mean offsets of 0.02+/-0.01" in right ascension, and 0.01+/-0.02" in declination. A check of our photometry reveals a small, negative CLEAN-like bias on the level of 35{mu}Jy. We report on the catalog completeness, finding that 97% of FIRST-detected quasars are recovered in the new Stripe 82 radio catalog, while faint, extended sources are more likely to be resolved out by the resolution bias. We conclude with a discussion of the optical counterparts to the catalog sources, including 76 newly detected radio quasars.
- ID:
- ivo://CDS.VizieR/J/ApJ/777/157
- Title:
- 90GHz obs. of high-mass star-forming regions
- Short Name:
- J/ApJ/777/157
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The chemical changes of high-mass star-forming regions provide a potential method for classifying their evolutionary stages and, ultimately, ages. In this study, we search for correlations between molecular abundances and the evolutionary stages of dense molecular clumps associated with high-mass star formation. We use the molecular line maps from Year 1 of the Millimetre Astronomy Legacy Team 90GHz (MALT90) Survey. The survey mapped several hundred individual star-forming clumps chosen from the ATLASGAL survey to span the complete range of evolution, from prestellar to protostellar to H II regions. The evolutionary stage of each clump is classified using the Spitzer GLIMPSE/MIPSGAL mid-IR surveys. Where possible, we determine the dust temperatures and H_2_ column densities for each clump from Herschel/Hi-GAL continuum data. From MALT90 data, we measure the integrated intensities of the N_2_H^+^, HCO^+^, HCN and HNC(1-0) lines, and derive the column densities and abundances of N_2_H^+^ and HCO^+^. The Herschel dust temperatures increase as a function of the IR-based Spitzer evolutionary classification scheme, with the youngest clumps being the coldest, which gives confidence that this classification method provides a reliable way to assign evolutionary stages to clumps. Both N_2_H^+^ and HCO^+^ abundances increase as a function of evolutionary stage, whereas the N_2_H^+^(1-0) to HCO^+^(1-0) integrated intensity ratios show no discernable trend. The HCN(1-0) to HNC(1-0) integrated intensity ratios show marginal evidence of an increase as the clumps evolve.
- ID:
- ivo://CDS.VizieR/J/A+A/482/483
- Title:
- GHz-peaked spectrum (GPS) sources
- Short Name:
- J/A+A/482/483
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Gigahertz-peaked spectrum (GPS) sources and high frequency peakers (HFPs) are among the smallest of active galactic nuclei currently believed to represent the earliest phases in the evolution of extragalactic radio sources. Recently there has been evidence of contamination by other types of radio sources among the GPS and HFP samples, but the confirmed GPS sources or HFPs also seem to form a very heterogeneous population. We study the statistical clustering of the GPS sources and the HFPs by taking as many source parameters as possible to find homogeneous groups among the sources. We expect the clustering to give us insight into the physical parameters that play a role in different source populations. We have collected a sample of 206 GPS sources and HFPs from the literature and gathered a massive database of various source properties, such as the redshift, the size, the polarization, the magnitudes, and the properties of the radio continuum. To visualize and to cluster these multidimensional data we used self-organising maps (SOM), which are neural networks trained by an unsupervised algorithm. We have classified the sources with an auxiliary classification to trace the locations of different types of radio continuum spectra on the map.