We present the first results from the Distant Radio Galaxies Optically Non-detected in the SDSS (DRaGONS) survey. Using a novel selection technique for identifying high-redshift radio galaxy (HzRG) candidates, a large sample is compiled using bright (S_1.4GHz_>100mJy) radio sources from the FIRST survey having no optical counterpart in the SDSS. Near-IR K-band imaging for 96 targets allows preliminary identification of HzRG candidates through the well-known K-z relation, for subsequent spectroscopic observation. We measure magnitudes brighter than K~19.5 for 70 of the 96, and limiting magnitudes for the remainder. Redshifts based on a linear fit to the K-z diagram give a mean <z>=2.5 and median z=2.0, showing that this method should be efficient at identifying a large number of HzRGs.
We present results of deep polarization imaging at 1.4GHz with the Dominion Radio Astrophysical Observatory as part of the DRAO Planck Deep Fields project. This deep extragalactic field covers 15.16deg^2^ centered at RA(J2000)=16:14 and DE(J2000)=54:56, has an angular resolution of 42"x62" at the field center, and reaches a sensitivity of 55uJy/beam in Stokes I and 45uJy/beam in Stokes Q and U. We detect 958 radio sources in Stokes I of which 136 are detected in polarization. We present the Euclidean-normalized polarized differential source counts down to 400uJy. These counts indicate that sources have a higher degree of fractional polarization at fainter Stokes I flux density levels than for brighter sources, confirming an earlier result. We find that the majority of our polarized sources are steep-spectrum objects with a mean spectral index of -0.77, and there is no correlation between fractional polarization and spectral index. We also matched deep field sources to counterparts in the Faint Images of the Radio Sky at Twenty Centimeters catalog. Of the polarized sources, 77% show structure at the arcsecond scale whereas only 38% of the sources with no detectable polarization show such structure. The median fractional polarization for resolved sources is 6.8%, while it is 4.4% for compact objects. The polarized radio sources in our deep field are predominantly those sources which are resolved and show the highest degrees of fractional polarization, indicating that the lobe dominated structure may be the source of the highly polarized sources. These resolved radio galaxies dominate the polarized source counts at P_0_=(Q^2^+U^2^)^0.5^<3mJy.
This catalog contains 1692 radio sources observed with the Penticton synthesis telescope at 408 MHz and at 1420 MHz. The catalog is comprised of sources detected in the P-surveys 1P through 9P, 12P through 15P, and 20P through 27P (see the "References" section below). The database was provided by R.Roger & C.R.Purton in May 1990 and an update of the data with further P-surveys is currently in progress.
This paper presents results from a continuum radio survey of a complete sample of 248 southern E and S0 galaxies. All the galaxies were observed at 2.7GHz (11cm) with the Parkes radio telescope, and those detected were reobserved at 5.0 GHz (6 cm). Thirty-seven galaxies were detected above a level of 25-30mJy, and a consideration of the background source density at 2.7GHz indicates that no more than two or three of these detections are due to background sources.
Low surface brightness galaxies (LSBGs) are defined as galaxies that are fainter than dark night sky and are important for studying our universe. Particularly, edge-on galaxies are useful for the study of rotational velocity and dynamical properties of galaxies. Hence here we focus on searching for edge-on LSBGs. In order to find these edge-on dim galaxies, a series of effects caused by inclination, including the surface brightness profile, internal extinction, and scale length, have been corrected. In this work, we present a catalog of 281 edge-on LSBG candidates, which are selected from the crossmatch between Sloan Digital Sky Survey Data Release 7 and the 40% ALFALFA catalog. We also present the properties of these edge-on LSBG candidates including the absolute magnitude, central surface brightness, B-V color, scale length, and relative thickness. Our result suggests that the correction of inclination effects is very important for obtaining a complete sample of LSBGs.
We present observations of the European Large-Area ISO Survey-North 1 (ELAIS-N1) at 325MHz using the Giant Metrewave Radio Telescope (GMRT), with the ultimate objective of identifying active galactic nuclei and starburst galaxies and examining their evolution with cosmic epoch. After combining the data from two different days we have achieved a median rms noise of ~40uJy/beam, which is the lowest that has been achieved at this frequency. We detect 1286 sources with a total flux density above ~270uJy. In this paper, we use our deep radio image to examine the spectral indices of these sources by comparing our flux density estimates with those of Garn et al. 2008 (Cat. J/MNRAS/383/75) at 610MHz with the GMRT, and surveys with the Very Large Array at 1400MHz. We attempt to identify very steep spectrum sources which are likely to be either relic sources or high-redshift objects as well as inverted-spectra objects which could be Giga-Hertz Peaked Spectrum objects. We present the source counts, and report the possibility of a flattening in the normalized differential counts at low flux densities which has so far been reported at higher radio frequencies.
Understanding the low-frequency radio sky in depth is necessary to subtract foregrounds in order to detect the redshifted 21 cm signal of neutral hydrogen from the cosmic dawn, the epoch of reionization and the post-reionization era. In this second paper of the series, we present the upgraded Giant Metrewave Radio Telescope (uGMRT) observation of the ELAIS N1 field made at 300-500MHz. The image covers an area of ~1.8deg^2^ and has a central background rms noise of ~15uJy/beam. We present a radio source catalogue containing 2528 sources (with flux densities >100uJy) and normalized source counts derived from that. A detailed comparison of detected sources with previous radio observations is shown. We discuss flux-scale accuracy, positional offsets, spectral index distribution and correction factors in source counts. The normalized source counts are in agreement with previous observations of the same field, as well as model source counts from the Square Kilometre Array Design Study simulation. It shows a flattening below ~1mJy that corresponds to a rise in populations of star-forming galaxies and radio-quiet active galactic nuclei. For the first time, we estimate the spectral characteristics of the angular power spectrum or multi-frequency angular power spectrum of diffuse Galactic synchrotron emission over a wide frequency bandwidth of 300-500MHz from radio interferometric observations. This work demonstrates the improved capabilities of the uGMRT.
In the local universe, high-power radio galaxies live in lower-density environments than low-luminosity radio galaxies. If this trend continued to higher redshifts, powerful radio galaxies would serve as efficient probes of moderate redshift groups and poor clusters. Photometric studies of radio galaxies at 0.3<~z<~0.5 suggest that the radio luminosity-environment correlation disappears at moderate redshifts, though this could be the result of foreground/background contamination affecting the photometric measures of environment. We have obtained multi-object spectroscopy in the fields of 14 lower luminosity (L_1.4GHz_<4x10^24^W/Hz) and higher luminosity (L_1.4GHz_>1.2x10^25^W/Hz) radio galaxies at z~0.3 to spectroscopically investigate the link between the environment and the radio luminosity of radio galaxies at moderate redshifts. Our results support the photometric analyses; there does not appear to be a correlation between the luminosity of a radio galaxy and its environment at moderate redshifts. Hence, radio galaxies are not efficient signposts for group environments at moderate redshifts.
Extragalactic peaked-spectrum radio sources are thought to be the progenitors of larger, radio-loud active galactic nuclei (AGN). Synchrotron self-absorption (SSA) has often been identified as the cause of their spectral peak. The identification of new megahertz-peaked spectrum sources from the GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey provides an opportunity to test how radio sources with spectral peaks below 1GHz fit within this evolutionary picture. We observed six peaked-spectrum sources selected from the GLEAM survey, three that have spectral characteristics which violate SSA and three that have spectral peaks below 230MHz, with the Very Long Baseline Array at 1.55 and 4.96 GHz. We present milliarcsecond resolution images of each source and constrain their morphology, linear size, luminosity, and magnetic field strength. Of the sources that are resolved by our study, the sources that violate SSA appear to be compact doubles, while the sources with peak frequencies below 230MHz have core-jet features. We find that all of our sources are smaller than expected from SSA by factors of >~20. We also find that component magnetic field strengths calculated from SSA are likely inaccurate, differing by factors of >~5 from equipartition estimates. The calculated equipartition magnetic field strengths more closely resemble estimates from previously studied gigahertz-peaked spectrum sources. Exploring a model of the interaction between jets and the interstellar medium, we demonstrate that free-free absorption (FFA) can accurately describe the linear sizes and peak frequencies of our sources. Our findings support the theory that there is a fraction of peaked-spectrum sources whose spectral peaks are best modelled by FFA, implying our understanding of the early stages of radio AGN is incomplete.
The catalog is a compilation of all published optical identifications of extragalactic radio sources. This machine-readable version is an updated and greatly expanded edition of the original published one; this version contains 14585 identifications and citations to 917 papers. The data file contains most commonly used source name, number in the 4C catalog Gower et al. (1967), and Pilkington and Scott (1965) if applicable, right ascension and declination (equinox B1950.0), magnitude estimate for the identification type of optical object, identification reference, alternate name for identified object (if known), confirmation or invalidation code and associated reference, finding chart existence (or nonexistence), redshift, and reference for the spectrum. A reference file contains the references ordered by number cited in the catalog and alphabetically by author. Completeness has been attempted for all papers published through the end of 1982. The present version contains fewer references than the 1974 version (which had 935) because certain numbers were unused in the previous edition and because certain references are no longer used in the 1983 version and were removed. The authors have prepared this final version and have discontinued future updates.
