- ID:
- ivo://CDS.VizieR/J/AJ/158/31
- Title:
- Kepler K2 mission fields 3-5: radio continuum survey
- Short Name:
- J/AJ/158/31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Murchison Widefield Array (MWA) monitoring of the Kepler K2 mission fields 3, 4, and 5 at frequencies of 155 and 186 MHz, from observations contemporaneous with the K2 observations. This work follows from previous MWA and Giant Metrewave Radio Telescope (GMRT) surveys of field 1, with the current work benefiting from a range of improvements in the data processing and analysis. We continue to build a body of systematic low-frequency blind surveys overlapping with transient/variable survey fields at other wavelengths, providing multiwavelength data for object classes such as flare stars. From the current work, we detect no variable objects at a surface density above 2x10^-4^ per square degree, at flux densities of ~500 mJy, and an observation cadence of days to weeks, representing almost an order of magnitude decrease in the measured upper limits compared to previous results in this part of observational parameter space. This continues to show that radio transients at meter and centimeter wavelengths are rare.
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Search Results
442. KGS EoR0 Catalogue
- ID:
- ivo://CDS.VizieR/J/MNRAS/461/4151
- Title:
- KGS EoR0 Catalogue
- Short Name:
- J/MNRAS/461/4151
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Detection of the epoch of reionization HI signal requires a precise understanding of the intervening galaxies and AGN, both for instrumental calibration and foreground removal. We present a catalogue of 7394 extragalactic sources at 182MHz detected in the RA=0 field of the Murchison Widefield Array Epoch of Reionization observation programme. Motivated by unprecedented requirements for precision and reliability we develop new methods for source finding and selection. We apply machine learning methods to self-consistently classify the relative reliability of 9490 source candidates. A subset of 7466 are selected based on reliability class and signal-to-noise ratio criteria. These are statistically cross-matched to four other radio surveys using both position and flux density information. We find 7369 sources to have confident matches, including 90 partially resolved sources that split into a total of 192 sub-components. An additional 25 unmatched sources are included as new radio detections. The catalogue sources have a median spectral index of -0.85. Spectral flattening is seen towards lower frequencies with a median of -0.71 predicted at 182MHz. The astrometric error is 7-arcsec compared to a 2.3-arcmin beam FWHM. The resulting catalogue covers ~1400deg^2^ and is complete to approximately 80mJy within half beam power. This provides the most reliable discrete source sky model available to date in the MWA EoR0 field for precision foreground subtraction.
- ID:
- ivo://CDS.VizieR/J/A+AS/132/31
- Title:
- Kinematical models for double radio sources
- Short Name:
- J/A+AS/132/31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- These tables contain structural parameters for a large sample of classical FR II (Fanaroff-Riley II, 1974MNRAS.167p..31F) double radio sources obtained from the literature.
- ID:
- ivo://CDS.VizieR/J/ApJ/753/62
- Title:
- Kinematic distance ambiguity in HII regions
- Short Name:
- J/ApJ/753/62
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using H I absorption spectra from the International Galactic Plane Survey, a new method is implemented to resolve the kinematic distance ambiguity for 75 H II regions with known systemic velocities from radio recombination lines. A further 40 kinematic distance determinations are made for H II region candidates without known systemic velocities through an investigation of the presence of H I absorption around the terminal velocity. New kinematic distance determinations can be used to further constrain spiral arm parameters and the location and extent of other structures in the Milky Way disk. H I absorption toward continuum sources beyond the solar circle is also investigated. Follow-up studies of H I at higher resolution than the 1' to 2' of existing Galactic Plane Surveys will provide kinematic distances to many more H II regions on the far side of the Galactic center. On the basis of the velocity channel summation technique developed in this paper, a much larger sample of H II regions will be analyzed in a future paper to remove the near-far distance ambiguity.
- ID:
- ivo://CDS.VizieR/J/MNRAS/355/20
- Title:
- K magnitudes of 74MHz radio sources
- Short Name:
- J/MNRAS/355/20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we present near-infrared K-band imaging of a sample of ultra-steep-spectrum (USS) radio sources selected at 74-MHz. The dual selection criteria of low frequency and USS mean that we should be sensitive to the highest-redshift (z>5) radio galaxies. We have obtained K-band magnitudes for all of the objects in our sample of 26 and discuss the properties of each.
- ID:
- ivo://CDS.VizieR/J/MNRAS/426/2107
- Title:
- KNoWS pilot bright sample
- Short Name:
- J/MNRAS/426/2107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- During 2010-11, the Medicina 32-m dish hosted the seven-feed 18-26.5GHz receiver built for the Sardinia Radio Telescope, with the goal to perform its commissioning. This opportunity was exploited to carry out a pilot survey at 20GHz over the area for {delta}>+72.3{deg}. This paper describes all the phases of the observations, as they were performed using new hardware and software facilities. The map-making and source extraction procedures are illustrated. A customized data reduction tool was used during the follow-up phase, which produced a list of 73 confirmed sources down to a flux density of 115mJy. The resulting catalogue, presented here, is complete above 200mJy. Source counts are in agreement with those provided by the Australia Telescope 20GHz (AT20G) survey. This pilot activity paves the way for a larger project, the K-band Northern Wide Survey (KNoWS), whose final aim is to survey the whole Northern hemisphere down to a flux limit of 50mJy (5{sigma}).
- ID:
- ivo://CDS.VizieR/J/A+A/601/A80
- Title:
- LABOCA 345GHz observations of Sgr A*
- Short Name:
- J/A+A/601/A80
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on a statistical analysis of the 345GHz submillimeter (submm) and 100GHz radio flux density distribution of Sagittarius A* (Sgr A*). The submm data set consists of 345GHz data obtained from different Large Apex Bolometer Camera (LABOCA) campaigns between 2008 and 2014, and additional literature data from 2004 to 2009 at comparable wavelengths. The radio observations were carried out with the Australia Telescope Compact Array (ATCA) between 2010 and 2014. We used a combined maximum likelihood estimator (MLE) and Kolmogorov-Smirnov (KS) statistics method to test for a possible power-law distribution in the high flux density excursions (flares) at both wavebands. We find that both flux density distributions can be described by a shifted power-law of the form p(x){prop.to}(x-S)^-{alpha}^ with {alpha}~4 (submm: {alpha}=4.0+/-1.7, radio: {alpha}=4.7+/-0.8). The same power-law index was previously found for the near-infrared (NIR) flux density distribution. These results may strengthen our preferred flare emission model: a combined synchrotron self-Compton (SSC) and adiabatically expanding self-absorbed synchrotron blob model where the flaring activity across all wavebands stem from the same source components and the variable emission can be described by a single state red noise process. Within the framework of the expanding blob model the similarity of the radio and the submm flux density distribution may also narrow down possible initial synchrotron turnover {nu}_0_ to be mainly around 350GHz and possible expansion velocities v_exp_ to be predominantly around 0.01c.
448. LARGESS survey
- ID:
- ivo://CDS.VizieR/J/MNRAS/464/1306
- Title:
- LARGESS survey
- Short Name:
- J/MNRAS/464/1306
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the Large Area Radio Galaxy Evolution Spectroscopic Survey (LARGESS), a spectroscopic catalogue of radio sources designed to include the full range of radio AGN populations out to redshift z~0.8. The catalogue covers ~800deg^2^ of sky, and provides optical identifications for 19179 radio sources from the 1.4GHz Faint Images of the Radio Sky at Twenty-cm (FIRST) survey down to an optical magnitude limit of i_mod_<20.5 in Sloan Digital Sky Survey (SDSS) images. Both galaxies and point-like objects are included, and no colour cuts are applied. In collaboration with the WiggleZ and Galaxy And Mass Assembly (GAMA) spectroscopic survey teams, we have obtained new spectra for over 5000 objects in the LARGESS sample. Combining these new spectra with data from earlier surveys provides spectroscopic data for 12329 radio sources in the survey area, of which 10 856 have reliable redshifts. 85 per cent of the LARGESS spectroscopic sample are radio AGN (median redshift z=0.44), and 15 per cent are nearby star-forming galaxies (median z=0.08). Low-excitation radio galaxies (LERGs) comprise the majority (83 per cent) of LARGESS radio AGN at z<0.8, with 12 per cent being high-excitation radio galaxies (HERGs) and 5 per cent radio-loud QSOs. Unlike the more homogeneous LERG and QSO sub-populations, HERGs are a heterogeneous class of objects with relatively blue optical colours and a wide dispersion in mid-infrared colours. This is consistent with a picture in which most HERGs are hosted by galaxies with recent or ongoing star formation as well as a classical accretion disc.
- ID:
- ivo://CDS.VizieR/J/MNRAS/414/2528
- Title:
- LBA Calibrator Survey (LCS1)
- Short Name:
- J/MNRAS/414/2528
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalogue of accurate positions and correlated flux densities for 410 flat-spectrum, compact extragalactic radio sources previously detected in the AT20G survey. The catalogue spans the declination range [-90{deg}, -40{deg}] and was constructed from four 24-hour VLBI observing sessions with the Australian Long Baseline Array at 8.3GHz. The VLBI detection rate in these experiments is 97%, the median uncertainty of the source positions is 2.6mas, and the median correlated flux density on projected baselines longer than 1000km is 0.14Jy. The goals of this work are 1) to provide a pool of southern sources with positions accurate to a few milliarcsec, which can be used for phase referencing observations, geodetic VLBI and space navigation; 2) to extend the complete flux-limited sample of compact extragalactic sources to the southern hemisphere; and 3) to investigate the parsec-scale properties of high-frequency selected sources from the AT20G survey. As a result of this VLBI campaign, the number of compact radio sources south of declination -40 deg which have measured VLBI correlated flux densities and positions known to milliarcsec accuracy has increased by a factor of 3.5. The catalogue and supporting material is available at http://astrogeo.org/lcs1.
- ID:
- ivo://CDS.VizieR/J/ApJS/174/481
- Title:
- 2LC Compact Radio Sources in the galactic center
- Short Name:
- J/ApJS/174/481
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used the VLA at 1.4GHz to survey the inner 2{deg} of the Galactic center for radio pulsar candidates. Because of the large pulse broadening suffered by Galactic center radio pulsars, our strategy has been to identify compact radio sources, without regard to whether they are pulsed radio sources. We describe our survey and present the catalog of 170 sources. Comparison with other radio surveys of the area shows that just over half of these sources have not been detected previously; this same comparison reveals 29 sources that are not in higher frequency surveys, suggesting that the sources are either variable or steep spectrum, and a comparable number of sources in other surveys that should have been detected in this survey but were not. Comparison with infrared surveys shows that 59 (35%) sources have infrared counterparts and are likely to be HII regions.
