In this paper, we investigate radio properties of active galaxies taken from the reference Veron-Cetty & Veron (2010, Cat. VII/258) catalog. The galaxies are limited to magnitudes in the range of 12^m^-19^m^. We have cross-correlated the list with radio catalogs and selected those galaxies that have data on six or more radio fluxes at different wavelengths. As a result, we have 198 galaxies that satisfy these conditions. Using SDSS DR15, we have obtained 96 spectroscopic identifications of the 198 objects. After the classification, 85% of the 96 objects have changed their types. Available data on the classification of these objects and our classification showed that 56.7% of them are Seyfert galaxies. For all the objects, we have built radio spectra and estimated radio spectral indices. As a result, we obtain {alpha}>=-0.6089+/-0.056> ({alpha}_Seyfert_=-0.6013+/-0.027, {alpha}_LINER_=-0.5955+/-0.025, {alpha}_HII_=-0.6672+/-0.039, {alpha}_Comp._=-0.7128+/-0.043). We discuss the radio properties of active galaxies based on their radio spectral indices.
We have used the Very Large Array, linked with the Pie Town Very Long Baseline Array antenna, to determine astrometric positions of 46 radio stars in the International Celestial Reference Frame (ICRF). Positions were obtained in the ICRF directly through phase referencing of the stars to nearby ICRF quasars whose positions are accurate at the 0.25mas level. Radio star positions are estimated to be accurate at the 10mas level, with position errors approaching a few milliarcseconds for some of the stars observed. Our measured positions were combined with previous measurements taken from as early as 1978 to obtain proper-motion estimates for all 46 stars with average uncertainties of ~1.7mas/yr.
Radio stars for linking celestial reference frames
Short Name:
J/A+AS/122/529
Date:
21 Oct 2021
Publisher:
CDS
Description:
Radio stars play a key role in establishing the link between optical reference frames and the conventional celestial reference frame based on extragalactic radio sources. The relevant astrometric, astrophysical and radio quantities are compiled of 66 cardinal radio stars currently suited to frame connection and main tenance of the link. The catalogue entries are supplied with ample bibliographical codes and annotations for easy data retrieval.
Images of resolved radio sources in the Palomar Bright Quasar Survey are presented with an angular resolution of 0.5 and 18arcsec. The observed structure of some well resolved radio quiet quasars and AGN's show large scale linear structures or unresolved central cores similar to radio loud objects in the BQS sample as well as the more luminous radio selected quasars. We suggest that at least some of these less luminous radio quiet objects may contain compact central engines characteristic of radio loud quasars and radio galaxies.
A 29.3deg^2 region surrounding the north ecliptic pole (NEP; R.A.=18h00m, Dec.=+66d30m) was mapped with the Very Large Array at 1.5GHz to support the deepest portion of the ROSAT all-sky soft X-ray survey. The resulting VLA-NEP survey catalog contains 2435 radio sources with flux densities in the range of 0.3-1000mJy, including over 200 fainter than 1mJy. The 28 fields of the inner 1.5deg have noise levels sigma ~=60uJy, and the 85 fields centered between 1.5deg and 3.0deg from the NEP have sigma ~=120uJy. The typical spatial resolution is 20" HPBW, and most positions are accurate to <2". Approximately 6% of the sources are found to be extended with size >30". We have compared the VLA-NEP catalog with four other radio catalogs made at lower resolution, as well as with the NASA Extragalactic Database and find counterparts for ~18% of the VLA-NEP objects. The normalized, differential radio source count is in agreement with the previous studies. Between 1 and 150mJy the slope of the logN-logS relation is 0.68+/-0.03.
We present the results of a deep 610-MHz survey of the 1^H^ XMM-Newton/Chandra survey area with the Giant Metre-wave Radio Telescope. The resulting maps have a resolution of ~7arcsec and an rms noise limit of 60Jy. To a 5{sigma} detection limit of 300Jy, we detect 223 sources within a survey area of 64arcmin in diameter. We compute the 610-MHz source counts and compare them to those measured at other radio wavelengths.
We aim to increase the sample of ultracool dwarfs studied in the radio domain to allow a more statistically significant understanding of the physical conditions associated with these magnetically active objects. We conducted a volume-limited survey at 4.9GHz of 32 nearby ultracool dwarfs with spectral types covering the range M7-T8. A statistical analysis was performed on the combined data from the present survey and previous radio observations of ultracool dwarfs.
The Australia Telescope Compact Array (ATCA) has been used at 1.38 and 2.38GHz to survey seven southern Abell clusters of galaxies with high X-ray luminosities: A2746, A2837, A3126, A3216, A3230, A3827 and A3836. The clusters have also been surveyed at 0.843GHz with the Molonglo Observatory Synthesis Telescope (MOST). We have listed a complete 1.38-GHz sample of 149 radio sources within the Abell circles centred on their X-ray centroids. We compare their identification fractions, emitted 1.38-GHz and optical powers, radio spectral indices and radial variation in projected source density with those of the radio-selected samples of Slee et al. (1998AuJPh..51..971S). We compare our fractional radio luminosity function with that of the radio-selected samples of Ledlow and Owen (1996AJ....112....9L) and Slee et al. (1998AuJPh..51..971S). Three significant differences are noted between X-ray and radio-selected samples of clusters; (1) the X-ray sample has an excess of flat-spectrum radio sources; (2) the fractional radio luminosity function for the FR I sources in the X-ray selected sample is much steeper, implying that fewer of their cluster galaxies become hosts for the stronger FR I radio galaxies; (3) a complete absence of FR II radio galaxies in the X-ray selected sample. The average excess projected density of radio sources near our cluster centres is approx. 5 times the background source density.
