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- 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/ApJ/829/119
- Title:
- Known pulsars identified in the TGSS ADR
- Short Name:
- J/ApJ/829/119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used the 150MHz radio continuum survey (TGSS ADR) from the Giant Metrewave Radio Telescope (GMRT) to search for phase-averaged emission toward all well-localized radio pulsars north of -53{deg} decl. We detect emission toward 200 pulsars with high confidence (>=5{sigma}) and another 88 pulsars at fainter levels. We show that most of our identifications are likely from pulsars, except for a small number where the measured flux density is confused by an associated supernova or pulsar-wind nebula, or a globular cluster. We investigate the radio properties of the 150MHz sample and find an unusually high number of gamma-ray binary millisecond pulsars with very steep spectral indices. We also note a discrepancy in the measured flux densities between GMRT and LOFAR pulsar samples, suggesting that the flux density scale for the LOFAR pulsar sample may be in error by approximately a factor of two. We carry out a separate search of 30 well-localized gamma-ray, radio-quiet pulsars in an effort to detect a widening of the radio beam into the line of sight at lower frequencies. No steep-spectrum emission was detected either toward individual pulsars or in a weighted stack of all 30 images.
- 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/ApJS/228/22
- Title:
- Korean VLBI Network Calibrator Survey (KVNCS). I.
- Short Name:
- J/ApJS/228/22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the catalog of the KVN Calibrator Survey (KVNCS). This first part of the KVNCS is a single-dish radio survey simultaneously conducted at 22 (K band) and 43GHz (Q band) using the Korean VLBI Network (KVN) from 2009 to 2011. A total of 2045 sources are selected from the VLBA Calibrator Survey with an extrapolated flux density limit of 100mJy at the K band. The KVNCS contains 1533 sources in the K band with a flux density limit of 70mJy and 553 sources in the Q band with a flux density limit of 120mJy; it covers the whole sky down to -32.5{deg} in decl. We detected 513 sources simultaneously in the K and Q bands; ~76% of them are flat-spectrum sources (-0.5<={alpha}<=0.5). From the flux-flux relationship, we anticipated that most of the radiation of many of the sources comes from the compact components. The sources listed in the KVNCS therefore are strong candidates for high-frequency VLBI calibrators.
- 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.
- ID:
- ivo://CDS.VizieR/J/A+A/606/A142
- Title:
- L1544 1.2 and 2mm emission maps
- Short Name:
- J/A+A/606/A142
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In dense and cold molecular clouds dust grains are surrounded by thick icy mantles. It is however not clear if dust growth and coagulation take place before the switch-on of a protostar. This is an important issue, as the presence of large grains may affect the chemical structure of dense cloud cores, including the dynamically important ionization fraction, and the future evolution of solids in protoplanetary disks. To study this further, we focus on L1544, one of the most centrally concentrated pre-stellar cores on the verge of star formation, and with a well-known physical structure. We observed L1544 at 1.2 and 2mm using NIKA, a new receiver at the IRAM 30 m telescope, and we used data from the Herschel Space Observatory archive. We find no evidence of grain growth towards the center of L1544 at the available angular resolution. Therefore, we conclude that single dish observations do not allow us to investigate grain growth towards the pre-stellar core L1544 and high sensitivity interferometer observations are needed. We predict that dust grains can grow to 200um in size toward the central ~300au of L1544. This will imply a dust opacity change by a factor of ~2.5 at 1.2mm, which can be detected using the Atacama Large Millimeter and submillimeter Array (ALMA) at different wavelengths and with an angular resolution of 2".
- ID:
- ivo://CDS.VizieR/J/A+A/537/A99
- Title:
- Large Quasar Astrometric Catalogue 2 (LQAC-2)
- Short Name:
- J/A+A/537/A99
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- First of all we make a substantial review of the definitions and properties of quasars and AGN (Active Galactic Nuclei), the differenciation of these objects being unclear in the literature and even for specialists. This will serve our purpose when deciding which kinds of objects will be taken into account in our compilation. Then we carry out the cross-identification between the 9 catalogues of quasars chosen for their accuracy and their huge number of objects, using a flag for each of them, and including all the available data related to magnitudes (infrared and optical), radiofluxes and redshifts. We also perform cross identification with external catalogues 2MASS, B1.0 and GSC2.3 in order to complete photometric data of the objects. Moreover we compute the absolute magnitude of our extragalactic objects by taking into account the recent studies concerning the galactic absorption. In addition substantial improvements are brought with respect to the first release of the LQAC (Souchay et al., 2009, Cat. J/A+A/494/799). At first a LQAC name is given for each object based on its equatorial coordinates with respect to the ICRS, following a procedure which creates no ambiguity for identification. At second the equatorial coordinates of the objects are recomputed more accurately according to the algorithms used for the elaboration of the Large Quasar Reference Frame (LQRF) (Andrei et al., 2009, Cat. I/313). At third we introduce a morphological classification for the objects which enables in particular to define clearly if the object is point-like or extended. Our final catalogue, called LQAC-2, contains 187 504 quasars. This is roughly larger than the 113 666 quasars recorded in the first version of the LQAC (Souchay et al., 2009, Cat. J/A+A/494/799) and a little more than the number of quasars recorded in the up-dated version of the Veron Cetty and Veron (2010, Cat. VII/258) catalogue, which was the densest compilation of quasars up to now. In addition to the quantitative and qualitative improvements brought by our compilation, we discuss the homogeneity of the data and carry out statistical analysis concerning the spatial density and the distance to the closest neighbour.
- ID:
- ivo://CDS.VizieR/J/A+A/583/A75
- Title:
- Large Quasar Astrometric Catalogue 3 (LQAC-3)
- Short Name:
- J/A+A/583/A75
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- From an astrometric point of view, quasars constitute quasi-ideal reference objects in the celestial sphere, with an a priori absence of proper motion. Since the second release of the Large Quasar Astrometric Catalog (LQAC), a large number of quasars have been discovered, in particular with the upcoming new release of the SDSS quasars catalog. Following the same procedure as in the two previous releases of the LQAC, our aim was to compile all the quasars recorded until the present date, with accurate recomputation of their equatorial coordinates in the ICRS and with the maximum of information concerning their physical properties, such as the redshift, the photometry, and the absolute magnitudes.
- ID:
- ivo://CDS.VizieR/J/A+A/494/799
- Title:
- Large Quasar Astrometric Catalogue (LQAC)
- Short Name:
- J/A+A/494/799
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The very large and increasing number of quasars reckoned from various sky surveys leads to a large quantity of data which brings various and inhomogeneous information in the fields of astrometry, photometry, radioastronomy and spectroscopy. In this paper, we describe our work that aims to make available a general compilation of the largest number of recorded quasars obtained from all the available catalogues, with their best position estimates, and providing physical information at both optical and radio wavelengths.
