- ID:
- ivo://CDS.VizieR/J/MNRAS/502/4779
- Title:
- 28-40GHz variability and polarimetry
- Short Name:
- J/MNRAS/502/4779
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We observed 51 sources in the Q-U-I JOint TEnerife (QUIJOTE) cosmological fields which were brighter than 1Jy at 30GHz in the Planck Point Source Catalogue (version 1), with the Very Large Array at 28-40GHz, in order to characterise their high-radio-frequency variability and polarization properties. We find a roughly log-normal distribution of polarization fractions with a median of 2%, in agreement with previous studies, and a median rotation measure (RM) of ~1110rad/m^2^ with one outlier up to ~64000rad/m^2^ which is among the highest RMs measured in quasar cores. We find hints of a correlation between the total intensity flux density and median polarization fraction. We find 59% of sources are variable in total intensity, and 100% in polarization at 3{sigma} level, with no apparent correlation between total intensity variability and polarization variability. This indicates that it will be difficult to model these sources without simultaneous polarimetric monitoring observations and they will need to be masked for cosmological analysis.
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- ID:
- ivo://CDS.VizieR/J/MNRAS/438/3058
- Title:
- 15GHz variability of {gamma}-ray blazars
- Short Name:
- J/MNRAS/438/3058
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from four years of twice-weekly 15GHz radio monitoring of about 1500 blazars with the Owens Valley Radio Observatory 40m telescope. Using the intrinsic modulation index to measure variability amplitude, we find that, with >6{sigma} significance, the radio variability of radio-selected {gamma}-ray-loud blazars is stronger than that of {gamma}-ray-quiet blazars. Our extended data set also includes at least 21 months of data for all AGN with 'clean' associations in the Fermi Large Area Telescope First AGN Catalog, 1LAC. With these additional data, we examine the radio variability properties of a {gamma}-ray-selected blazar sample. Within this sample, we find no evidence for a connection between radio variability amplitude and optical classification. In contrast, for our radio-selected sample we find that the BL Lac object subpopulation is more variable than the flat-spectrum radio quasar (FSRQ) subpopulation. Radio variability is found to correlate with the synchrotron peak frequency, with low- and intermediate-synchrotron-peaked blazars varying more than high-synchrotron-peaked ones. We find evidence for a significant negative correlation between redshift and radio variability among bright FSRQs.
- ID:
- ivo://CDS.VizieR/J/AJ/130/2529
- Title:
- 8.4GHz VLBI observations of Southern ICRF sources
- Short Name:
- J/AJ/130/2529
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 8.4GHz very long baseline interferometry (VLBI) observations of 48 southern hemisphere extragalactic sources from the International Celestial Reference Frame. These are the second in a series of observations intended to image all such sources in the southern hemisphere at milliarcsecond resolution and bring the total number of observed sources to 111. We use these data, together with previously published data, to quantify the magnitude of the expected effect of intrinsic source structure on astrometric bandwidth synthesis VLBI observations by calculating a "structure index" for the sources; the structure index yields an estimate of their astrometric quality.
- ID:
- ivo://CDS.VizieR/J/A+A/364/391
- Title:
- 86GHz VLBI survey of compact radio sources
- Short Name:
- J/A+A/364/391
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- File table1 contains the list of observed sources, providing the source coordinates (J2000) and redshift, detection status, type, optical magnitude, and brightness temperature of the radio emission. File table4 contains the description of the VLBI data, and provide the observed total and correlated flux densities, the parameters of single gaussian component model fits, and the parameters of hybrid images of the observed sources. File table5 contains multicomponent model fits for the sources with detected extended structures and the brightness temperatures derived from these model fits.
- ID:
- ivo://CDS.VizieR/J/A+A/546/A16
- Title:
- 22-GHz water maser clouds
- Short Name:
- J/A+A/546/A16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Cool, evolved stars undergo copious mass loss but the detailed mechanisms and the form in which the matter is returned the ISM are still under debate. We investigated the structure and evolution of the wind at 5 to 50 stellar radii from Asymptotic Giant Branch and Red Supergiant stars.
- ID:
- ivo://CDS.VizieR/J/PAZh/22/269
- Title:
- Giant branch and variable stars in NGC 3201
- Short Name:
- J/PAZh/22/269
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Accurate equatorial coordinates have been determined for variable stars in the globular cluster NGC 3201. Results of photographic BV photometry are presented.
- ID:
- ivo://CDS.VizieR/J/MNRAS/445/1745
- Title:
- Giant Gemini GMOS survey. I.
- Short Name:
- J/MNRAS/445/1745
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present spectra of 163 quasars at z_em_>4.4 taken with the Gemini Multi Object Spectrometers, the largest publicly available sample of high-quality (signal-to-noise ratio S/N~20 per 1.85{AA} pixel) low-resolution (full width at half maximum FWHM~320km/s) rest-frame ultraviolet quasar spectra at these redshifts. The sample was selected from SDSS Data Release 7 with the aim to obtain high-S/N follow-up spectra of the intergalactic HI Lyman series and Lyman continuum absorption at high redshift. Each quasar was observed with the GMOS B600 (FWHM~320km/s) and R400 (FWHM~360km/s) gratings to cover the rest-frame wavelength range from ~850 to ~1500{AA}. Here we make the spectra available in reduced form. The accompanying paper presents a detailed description the sample and a measurement of the mean free path to Lyman limit photons in the IGM, based on stacked rest-frame quasar spectra.
- ID:
- ivo://CDS.VizieR/J/AZh/62/229
- Title:
- Giant H II region Ratan-600 observations
- Short Name:
- J/AZh/62/229
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of observations of a giant H II region, situated at the longitudes 4-10deg, at the wavelength 7.6cm are presented. A catalogue has been compiled containing 63 sources for which the positions, flux densities, and angular dimensions have been determined. Forty-four objects with the fluxes P<1Jy and having small angular sizes have been detected. The radio brightness distribution of the background component of the galactic radio emission has been obtained. A weak background extended by more than 2deg in the galactic latitude has been registered. It is shown that the detected weak objects represent a more high-latitude population than the strong galactic sources and are probably associated with the weak extended background.
- ID:
- ivo://CDS.VizieR/J/MNRAS/460/1739
- Title:
- Giant HII regions BOND abundances
- Short Name:
- J/MNRAS/460/1739
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the Bayesian oxygen and nitrogen abundance determinations (bond) method. bond is a Bayesian code (available at: http://bond.ufsc.br) to simultaneously derive oxygen and nitrogen abundances in giant HII regions. It compares observed emission lines to a grid of photoionization models without assuming any relation between O/H and N/O. Our grid spans a wide range in O/H, N/O and ionization parameter U, and covers different starburst ages and nebular geometries. Varying starburst ages accounts for variations in the ionizing radiation field hardness, which arise due to the ageing of HII regions or the stochastic sampling of the initial mass function. All previous approaches assume a strict relation between the ionizing field and metallicity. The other novelty is extracting information on the nebular physics from semistrong emission lines. While strong lines ratios alone ([OIII]/H{beta}, [OII]/H{beta} and [NII]/H{beta}) lead to multiple O/H solutions, the simultaneous use of [ArIII]/[NeIII] allows one to decide whether an HII region is of high or low metallicity. Adding HeI/H{beta} pins down the hardness of the radiation field. We apply our method to HII regions and blue compact dwarf galaxies, and find that the resulting N/O versus O/H relation is as scattered as the one obtained from the temperature-based method. As in previous strong-line methods calibrated on photoionization models, the bond O/H values are generally higher than temperature-based ones, which might indicate the presence of temperature fluctuations or kappa distributions in real nebulae, or a too soft ionizing radiation field in the models.
- ID:
- ivo://nasa.heasarc/gmrtas150m
- Title:
- Giant Metrewave Radio Telescope All-Sky 150-MHz Radio Source Catalog
- Short Name:
- GMRTAS150M
- Date:
- 27 Sep 2024
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains results from the first full release of a survey of the 150-MHz radio sky, observed with the Giant Metrewave Radio Telescope (GMRT) between April 2010 and March 2012 as part of the TIFR GMRT Sky Survey (TGSS) project. Aimed at producing a reliable compact source survey, the authors' automated data-reduction pipeline efficiently processed more than 2000 hours of observations with minimal human interaction. Through application of innovative techniques such as image-based flagging, direction-dependent calibration of ionospheric phase errors, correcting for systematic offsets in antenna pointing, and improving the primary beam model, the authors created good quality images for over 95% of the 5,336 pointings. This data release covers 36,900 deg<sup>2</sup> (or 3.6 pi steradians) of the sky between -53 and +90 degrees Declination, which is 90% of the total sky. The majority of pointing images has a noise level below 5 mJy/beam (the median RMS background noise is 3.5 mJy per beam), with an approximate resolution of 25" x 25" (or 25" x 25"/cos(Dec-19<sup>o</sup>) for pointings south of 19 degrees Declination). The authors have produced a catalog of 0.62 Million radio sources with flux densities ranging from 11.1 mJy to 9.22 kJy that are derived from an initial, high-reliability source extraction at the 7-sigma level. For the bulk of the survey, the measured overall astrometric accuracy is better than 2 arcseconds in Right Ascension and Declination, while the flux density accuracy is estimated at approximately 10%. Within the scope of the TGSS Alternative Data Release (TGSS ADR) project, the source catalog, as well as 5,336 mosaic images (5 x 5 degree<sup>2</sup>) and an image cutout service, are made publicly available as a service to the astronomical community. (The TGSS images and cutout server are available through the project website at <a href="http://tgssadr.strw.leidenuniv.nl/">http://tgssadr.strw.leidenuniv.nl/</a>). In addition to enabling a wide range of different scientific investigations, the authors anticipate that these survey products will provide a solid reference for various new low-frequency radio aperture array telescopes (LOFAR, LWA, MWA, SKA-low), and can play an important role in characterizing the epoch-of-reionization (EoR) foreground. The TGSS ADR project aims at continuously improving the quality of the survey data products. Near-future improvements include replacement of bright source snapshot images with archival targeted observations, using new observations to fill the holes in sky coverage and to replace very poor quality observational data, and an improved flux calibration strategy for less severely affected observational data. This table was created by the HEASARC in February 2017 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/598/A78">CDS Catalog J/A+A/598/A78</a> file table3.dat. This is a service provided by NASA HEASARC .