Showing papers on "NRAO VLA Sky Survey published in 1999"
TL;DR: The Sydney University Molonglo Sky Survey ( SUMSS) as mentioned in this paper produces images with a resolution of 43'' × 43'' csc |δ| and an rms noise level of ~1 mJy beam-1.
Abstract: The Molonglo Observatory Synthesis Telescope, operating at 843 MHz with a 5 deg2 field of view, is carrying out a radio imaging survey of the sky south of declination -30°. This survey (the Sydney University Molonglo Sky Survey, or SUMSS) produces images with a resolution of 43'' × 43'' csc |δ| and an rms noise level of ~1 mJy beam-1. The SUMSS is therefore similar in sensitivity and resolution to the northern NRAO VLA Sky Survey. The survey is progressing at a rate of about 1000 deg2 per year, yielding individual and statistical data for many thousands of weak radio sources. This paper describes the main characteristics of the survey and presents sample images from the first year of observations.
476 citations
TL;DR: In this article, the first results of the search of new halo and relic candidates in the NRAO VLA Sky Survey were presented, where they inspected a sample of 205 clusters from the X-ray-brightest Abell-type clusters presented by Ebeling et al.
345 citations
TL;DR: In this article, the authors used the broad-band properties of high-energy peaked BL Lacs (HBLs) to identify a sample of 218 objects that is expected to include about 85% of all HBLs and that is therefore several times larger than all other published samples.
Abstract: We have assembled a multifrequency data base by cross-correlating the NRAO VLA Sky Survey (NVSS) catalogue of radio sources with the RASSBSC list of soft X-ray sources, obtaining optical magnitude estimates from the Palomar and UK Schmidt surveys as provided by the Automated Plate Measurement (APM) and COSMOS on-line services. By exploiting the nearly unique broad-band properties of high-energy peaked BL Lacs (HBL), we have statistically identified a sample of 218 objects that is expected to include about 85 per cent of BL Lacs and that is therefore several times larger than all other published samples of HBLs. Using a subset (155 objects) that is radio-flux-limited and statistically well-defined, we have derived the VVm distribution and the log N–log S of extreme HBLs (fxfr3×10-10 erg cm-2 s-1 Jy-1) down to 3.5 mJy. We find that the log N–log S flattens around 20 mJy and that 〈VVm〉=0.42±0.02. This extends to the radio band earlier results, based on much smaller X-ray-selected samples, about the anomalous cosmological observational properties of HBLs. A comparison with the expected radio log N–log S of all BL Lacs (based on a beaming model) shows that extreme HBLs make up roughly 2 per cent of the BL Lac population, independently of radio flux. This result, together with the flatness of the radio log N–log S at low fluxes, is in contrast with the predictions of a recent model that assumes an anticorrelation between peak frequency and bolometric luminosity. This scenario would in fact result in an increasing dominance of HBLs at lower radio fluxes; an effect that, if at all present, must start at fluxes fainter than our survey limit. The extreme fxfr flux ratios and high X-ray fluxes of these BL Lacs makes them good candidate TeV sources; some of the brighter (and closer) ones are possibly detectable with the current generation of Cerenkov telescopes. Statistical identification of sources based on their location in multiparameter space, of the kind described here, will have to become commonplace with the advent of the many large, deep surveys at various frequencies currently scheduled or under construction.
101 citations
TL;DR: In this article, radio observations of 87 optically selected quasars at 5 GHz with the VLA have been made to measure the radio power for these objects and hence determine how the fraction of radio-loud quaars varies with redshift and optical luminosity.
Abstract: We have made radio observations of 87 optically selected quasars at 5 GHz with the VLA in order to measure the radio power for these objects and hence determine how the fraction of radio-loud quasars varies with redshift and optical luminosity. The sample has been selected from the recently completed Edinburgh Quasar Survey and covers a redshift range of 0.3≤z≤1.5 and an optical absolute magnitude range of -26.5≤MB≤-23.5 (h=1/2, q0=1/2). We have also matched other existing surveys with the Faint Images of the Radio Sky at Twenty Centimeters and NRAO VLA Sky Survey radio catalogs and combined these data so that the optical luminosity-redshift plane is now far better sampled than before. We have fitted a model to the probability of a quasar being radio-loud as a function of absolute magnitude and redshift, and from this model we infer the radio-loud and radio-quiet optical luminosity functions. The radio-loud optical luminosity function is featureless and flatter than the radio-quiet one. It evolves at a marginally slower rate if quasars evolve by density evolution, but the difference in the rate of evolutions of the two different classes is much less than was previously thought. We show, using Monte Carlo simulations, that the observed difference in the shape of the optical luminosity functions can be partly accounted for by Doppler boosting of the optical continuum of the radio-loud quasars, and we explain how this can be tested in the future.
100 citations
TL;DR: In this paper, the authors presented the first results from a study of the radio continuum properties of galaxies in the 2dF Galaxy Redshift Survey (2dFGRS) based on thirty 2DF fields covering a total area of about 100 deg2.
Abstract: We present the first results from a study of the radio continuum properties of galaxies in the 2dF Galaxy Redshift Survey, (2dFGRS) based on thirty 2dF fields covering a total area of about 100 deg2. About 1.5% of galaxies with b_J < 19.4 mag. are detected as radio continuum sources in the NRAO VLA Sky Survey (NVSS). Of these, roughly 40% are star-forming galaxies and 60% are active galaxies (mostly low-power radio galaxies and a few Seyferts). The combination of 2dFGRS and NVSS will eventually yield a homogeneous set of around 4000 radio-galaxy spectra, which will be a powerful tool for studying the distribution and evolution of both AGN and starburst galaxies out to z ~ 0.3.
31 citations
TL;DR: In this paper, the IRAS point source catalog was used to construct a sample of planetary nebulae (PNe) unbiased by dust extinction, and the 1.4 GHz NRAO VLA Sky Survey (NVSS) images and source catalog were used to reject radio-quiet mid-infrared sources.
Abstract: In order to construct a sample of planetary nebulae (PNe) unbiased by dust extinction, we first selected the 1358 sources in the IRAS Point Source Catalog north of J2000 declination δ = -40° having measured S(25 μm) ≥ 1 Jy and colors characteristic of PNe: detections or upper limits consistent with both S(12 μm) ≤ 0.35S(25 μm) and S(25 μm) ≥ 0.35S(60 μm). The majority are radio-quiet contaminating sources such as asymptotic giant branch stars. Free-free emission from genuine PNe should make them radio sources. The 1.4 GHz NRAO VLA Sky Survey (NVSS) images and source catalog were used to reject radio-quiet mid-infrared sources. We identified 454 IRAS sources with radio sources brighter than S ≈ 2.5 mJy beam-1 (equivalent to T ≈ 0.8 K in the 45'' FHWM NVSS beam) by positional coincidence. They comprise 332 known PNe in the Strasbourg-ESO Catalogue of Galactic Planetary Nebulae and 122 candidate PNe, most of which lie at very low Galactic latitudes. Exploratory optical spectroscopic observations suggest that most of these candidates are indeed PNe optically dimmed by dust extinction, although some contamination remains from H II regions, Seyfert galaxies, etc. Furthermore, the NVSS failed to detect only 4% of the known PNe in our infrared sample. Thus it appears that radio selection can greatly improve the reliability of PN candidate samples without sacrificingcompleteness.
30 citations
TL;DR: In this paper, the ASCA SIS and the ROSAT PSPC spectral data of the SNR 3C397 were analyzed with a two-component non-equilibrium ionization model.
Abstract: The ASCA SIS and the ROSAT PSPC spectral data of the SNR 3C397 are analysed with a two-component non-equilibrium ionization model. Besides, the ASCA SIS0 and SIS1 spectra are also fitted simultaneously in an equilibrium case. The resulting values of the hydrogen column density yield a distance of $\sim8\kpc$ to 3C397. It is found that the hard X-ray emission, containing S and Fe K$\alpha$ lines, arises primarily from the hot component, while most of the soft emission, composed mainly of Mg, Si, Fe L lines, and continuum, is produced by the cool component. The emission measures suggest that the remnant evolves in a cloudy medium and imply that the supernova progenitor might not be a massive early-type star. The cool component is approaching ionization equilibrium. The ages estimated from the ionization parameters and dynamics are all much greater than the previous determination. We restore the X-ray maps using the ASCA SIS data and compare them with the ROSAT HRI and the NRAO VLA Sky Survey (NVSS) 20 cm maps. The morphology with two bright concentrations suggests a bipolar remnant encountering a denser medium in the west.
29 citations
TL;DR: In this paper, the ASCA SIS and ROSAT PSPC spectral data of the supernova remnant 3C 397 were analyzed with a two-component nonequilibrium ionization model.
Abstract: The ASCA SIS and ROSAT PSPC spectral data of the supernova remnant 3C 397 are analyzed with a two-component nonequilibrium ionization model. In addition, the ASCA SIS0 and SIS1 spectra are fitted simultaneously in an equilibrium case. The resulting values of the hydrogen column density yield a distance of ~8 kpc to 3C 397. It is found that the hard X-ray emission, containing S and Fe Kα lines, arises primarily from the hot component, while most of the soft emission, composed mainly of Mg, Si, and Fe L lines and continuum, is produced by the cool component. The emission measures suggest that the remnant evolves in a cloudy medium and imply that the supernova progenitor might not be a massive early-type star. The cool component is approaching ionization equilibrium. The ages estimated from the ionization parameters and dynamics are all much greater than the previous determination. We restore the X-ray maps using the ASCA SIS data and compare them with the ROSAT HRI and the NRAO VLA Sky Survey 20 cm maps. The morphology with two bright concentrations suggests a bipolar remnant encountering a denser medium in the west.
28 citations
TL;DR: In this paper, the total flux density, linear polarization intensity and polarization angle (PA) of all pulsars are extracted from the NRAO VLA Sky Survey (NVSS) catalog.
Abstract: We identified 97 strong pulsars from the NRAO VLA Sky Survey (NVSS) at 1.4 GHz north of Dec(J2000) -40°. The total flux density, linear polarization intensity and polarization angle (PA) of all pulsars are extracted from the NVSS catalog. The well-calibrated PA measurement of 5 pulsars can be used for absolute PA calibrations in other observations. Comparing the source positions with those in the pulsar catalog, we got the first measurement of the proper motion upper limit of PSR B0031-07, which is mas yr-1 and mas yr-1 .
27 citations
TL;DR: In this article, the first results from a study of the radio continuum properties of galaxies in the 2dF Galaxy Redshift Survey (2dFGRS) were presented, based on thirty 2DF fields covering a total area of about 100 square degrees.
Abstract: We present the first results from a study of the radio continuum properties of galaxies in the 2dF Galaxy Redshift Survey, based on thirty 2dF fields covering a total area of about 100 square degrees. About 1.5% of galaxies with b(J) < 19.4 mag are detected as radio continuum sources in the NRAO VLA Sky Survey (NVSS). Of these, roughly 40% are star-forming galaxies and 60% are active galaxies (mostly low-power radio galaxies and a few Seyferts). The combination of 2dFGRS and NVSS will eventually yield a homogeneous set of around 4000 radio-galaxy spectra, which will be a powerful tool for studying the distriibution and evolution of both AGN and starburst galaxies out to redshift z=0.3.
26 citations
TL;DR: In this paper, the authors made radio observations of J2114+820, a low-power radio galaxy with an angular size of 6′ and its radio structure basically consists of a prominent core, a jet directed in northwest direction and two extended S-shaped lobes.
Journal Article•
TL;DR: In this article, radio and optical observations of the pe- culiar radio galaxy J1835+620, a member of a new sample of large angular size radio galaxies selected from the NRAO VLA Sky Survey, were presented.
Abstract: We present radio and optical observations of the pe- culiar radio galaxy J1835+620, a member of a new sample of large angular size radio galaxies selected from the NRAO VLA Sky Survey. Its optical counterpart is in a group of at least three galaxies and shows strong, narrow emission lines which allow us to measure its redshift as z =0 :518. The derived cosmolog- ical distance places J1835+620 among the giant radio galaxies. The outstanding aspect of J1835+620 at radio wavelengths is the existence of two symmetric bright components within a typical Fanaroff-Riley type II structure. We interpret the source as the result of two distinct phases of core activity. Radio maps and radio polarization properties are consistent with a dense new ejection evolving through an older underlying jet. We suggest that interaction with nearby galaxies could be the reason for restarting the activity in J1835+620.
01 Jan 1999
TL;DR: The Sydney University Molonglo Sky Survey (SUMSS) as mentioned in this paper is a deep imaging survey of the southern radio sky at 843 MHz, which will cover 8000 square degrees of sky south of declination.
Abstract: The Sydney University Molonglo Sky Survey (SUMSS) is a deep imaging survey of the southern radio sky at 843 MHz. Over the next few years, it will cover 8000 square degrees of sky south of declination —30°. The survey’s resolution (43 aresec) and sensitivity (3σ detection limit 3–5 mJy) are similar to those of the northern NRAO VLA Sky Survey (NVSS). Some of the scientific problems which can be tackled with such a survey include the clustering of faint radio sources, identification of diffuse and giant sources, and the space distribution and evolution of star-forming galaxies. SUMSS data will be made publicly available as the survey progresses.
Posted Content•
TL;DR: The extended radio source G16.2-2.7 is detected as a new previously uncataloged Galactic supernova remnant as discussed by the authors, and its non-thermal radio spectrum has spectral index alpha=-0.51, with S_nu(1 GHz) = 2.08 Jy.
Abstract: The extended radio source G16.2-2.7 is detected as a new previously uncataloged Galactic supernova remnant. Its non-thermal radio spectrum has spectral index alpha=-0.51, with S_nu(1 GHz) = 2.08 Jy, as being measured with the RATAN-600 radio telescope. The NRAO VLA Sky Survey (NVSS) map at 1.4 GHz shows a shell-like bilateral structure. The similar smoothed image from the Effelsberg survey at 2.7 GHz is discussed. The angular diameter 17' of a circular shell is fitted to brightness peaks meanwhile the outer diameter D_max = 18.4' and the width Delta_R=1' are fitted with the model of a spherical optically thin hollow shell. The surface brightness of G16.2-2.7: Sigma(1GHz)= (1+-0.1)10^{-21} W Hz^{-1}m^{-2}sr^{-1}. The peaks in the shell arcs are highly polarized at 1.4 GHz.
Journal Article•
TL;DR: The extended radio source G16.2 2.7 is detected as a new previously uncataloged Galactic supernova remnant as discussed by the authors, with spectral index = 0:51, with S (1 GHz) = 2.08 Jy, as being measured with the RATAN- 600 radio telescope.
Abstract: The extended radio source G16.2 2.7 is detected as a new previously uncataloged Galactic supernova remnant. Its non-thermal radio spectrum has spectral index = 0:51, with S (1 GHz) = 2.08 Jy, as being measured with the RATAN- 600 radio telescope. The NRAO VLA Sky Survey (NVSS) map at 1.4 GHz shows a shell-like bilateral structure. The similar smoothed image from the Effelsberg survey at 2.7 GHz is dis- cussed. The angular diameter 17 0 of a circular shell is fitted to brightness peaks meanwhile the outer diameter Dmax = 18: 0 4 and the widthR=1 0 are fitted with the model of a spherical op- tically thin hollow shell. The surface brightness of G16.2 2.7: (1GHz) =( 10:1)10 21 WH z 1 m 2 sr 1 . The peaks in the shell arcs are highly polarized at 1.4 GHz.
TL;DR: In this paper, the first results of the search of new halo and relic candidates in the NRAO VLA Sky Survey were presented, where they inspected a sample of 205 clusters from the X-ray-brightest Abell-type clusters presented by Ebeling et al.
Abstract: We present the first results of the search of new halo and relic candidates in the NRAO VLA Sky Survey. We have inspected a sample of 205 clusters from the X-ray-brightest Abell-type clusters presented by Ebeling et al (1996), and found 29 candidates. Out of them, 11 clusters are already known from the literature to contain a diffuse cluster-wide source, while in 18 clusters this is the first indication of the existence of this type of sources. We classify these sources as halos or relics according to their location in the cluster center or periphery, respectively. We find that the occurrence of cluster halos and relics is higher in clusters with high X-ray luminosity and high temperature. We also confirm the correlation between the absence of a cooling flow and the presence of a radio halo at the cluster center.