- ID:
- ivo://CDS.VizieR/J/A+A/647/A50
- Title:
- Radio halos in mass selected clusters
- Short Name:
- J/A+A/647/A50
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Radio halos are synchrotron diffuse sources at the centre of a fraction of galaxy clusters. The study of large samples of clusters with adequate radio and X-ray data is necessary to investigate the origin of radio halos and their connection with the cluster dynamics and formation history. The aim of this paper is to compile a well-selected sample of galaxy clusters with deep radio observations to perform an unbiased statistical study of the properties of radio halos. We selected 75 clusters with M>=6x10^14^M_{sun}_ at z=0.08-0.33 from the Planck Sunyaev-Zel'dovich catalogue. Clusters without suitable radio data were observed with the Giant Metrewave Radio Telescope and/or the Jansky Very Large Array to complete the information about the possible presence of diffuse emission. We used archival Chandra X-ray data to derive information on the clusters' dynamical states. This observational campaign led to the detection of several cluster-scale diffuse radio sources and candidates that deserve future follow-up observations. Here we summarise their properties and add information resulting from our new observations. For the clusters where we did not detect any hint of diffuse emission, we derived new upper limits to their diffuse flux. We have built the largest mass-selected (>80% complete in mass) sample of galaxy clusters with deep radio observations available to date.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJS/135/155
- Title:
- Radio identification of 3EG EGRET sources
- Short Name:
- J/ApJS/135/155
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The method of Mattox et al. (1996ApJ...461..396M) for identifying EGRET sources with 5GHz radio sources has been applied to the 3EG EGRET catalog of Hartman et al. (1999, Cat. <J/ApJS/123/79>). Complete results are tabulated. We tabulate separately 46 EGRET sources with radio identifications which we expect to have a high probability of being correct. We suggest that these sources are appropriate for most studies of the properties of {gamma}-ray blazars as a class. All but one of these 46 sources were classified by Hartman et al. (1999, Cat. <J/ApJS/123/79>) as high-confidence identifications; and the additional source was classified by Hartman et al. (1999, Cat. <J/ApJS/123/79>) as a plausible identification. We also tabulate separately 37 additional "plausible identifications of EGRET sources with radio sources." These less secure possibilities include the remaining 21 "high-confidence identifications" of Hartman et al. (1999, Cat. <J/ApJS/123/79>), three of the 27 "lower confidence potential blazar identifications" of Hartman et al. (1999, Cat. <J/ApJS/123/79>), and an additional 15 plausible identifications which have not been suggested previously. Many of these sources require new radio and optical observations to establish them as blazars. We suggest that the 23 "lower-confidence potential blazar identifications" of Hartman et al. (1999, Cat. <J/ApJS/123/79>) which we do not find plausible should not be used in studies of the properties of the EGRET blazars. For this analysis, we have made elliptical fits to the 95% confidence contours of the position uncertainty regions of the 3EG sources.
- ID:
- ivo://CDS.VizieR/J/ApJ/481/95
- Title:
- Radio identification of EGRET sources
- Short Name:
- J/ApJ/481/95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a method to assess the reliability of the identification of EGRET sources with extragalactic radio sources. We verify that EGRET is detecting the blazar class of active galactic nuclei (AGNs). However many published identifications are found to be questionable. We provide a table of 42 blazars that we expect to be robust identifications of EGRET sources. This includes one previously unidentified EGRET source, the lensed AGN PKS 1830-210, near the direction of the Galactic center. We provide the best available positions for 16 more radio sources that are also potential identifications for previously unidentified EGRET sources. All high Galactic latitude EGRET sources (|b|>3) that demonstrate significant variability can be identified with flat-spectrum radio sources. This suggests that EGRET is not detecting any type of AGN other than blazars. This identification method has been used to establish with 99.998% confidence that the peak gamma-ray flux of a blazar is correlated with its average 5GHz radio flux. An even better correlation is seen between gamma-ray flux and the 2.29GHz flux density measured with VLBI at the base of the radio jet. Also, using high-confidence identifications, we find that the radio sources identified with EGRET sources have greater correlated VLBI flux densities than the parent population of flat radio spectrum sources.
- ID:
- ivo://CDS.VizieR/J/ApJS/159/282
- Title:
- 315 radio identified planetary nebulae
- Short Name:
- J/ApJS/159/282
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the 1.4GHz NRAO VLA Sky Survey (NVSS, Cat. <VIII/65>) images and source catalog, we identified 315 radio sources stronger than ~2.5mJy among over 1000 recently discovered planetary nebulae north of J2000 declination {delta}=-40{deg}. Two-thirds of these radio sources are weaker than 10mJy at 1.4GHz. This result is a uniform supplement to the previous NVSS radio identification of known PNe and a large homogeneous sample including over 1000 PNe with NVSS sources is obtained. By examining the radio properties of PNe, it is found that most of the planetary nebulae detected at both 1.4 and 5.0GHz are optically thick at {lambda}=20cm.
- ID:
- ivo://CDS.VizieR/J/A+A/574/A4
- Title:
- Radio image of Luminous Infrared Galaxies
- Short Name:
- J/A+A/574/A4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Luminous Infrared Galaxies (LIRGs) are systems enshrouded in dust, which absorbs most of their optical/UV emission and radiates it again in the mid- and far-infrared. Radio observations are largely unaffected by dust obscuration, enabling us to study the central regions of LIRGs in an unbiased manner. The main goal of this project is to examine how the radio properties of local LIRGs relate to their infrared spectral characteristics. Here we present an analysis of the radio continuum properties of a subset of the Great Observatories All-sky LIRG Survey (GOALS), which consists of 202 nearby systems (z<0.088). Our radio sample consists of 35 systems, containing 46 individual galaxies, that were observed at both 1.49 and 8.44GHz with the VLA with a resolution of about 1-arcsec (FWHM). The aim of the project is to use the radio imagery to probe the central kpc of these LIRGs in search of Active Galactic Nuclei (AGN). We used the archival data at 1.49 and 8.44GHz to create radio-spectral-index maps using the standard relation between flux density S{nu} and frequency {nu}, S{nu}~{nu}^-{alpha}^, where {alpha} is the radio spectral index. By studying the spatial variations in {alpha}, we classified the objects as radio-AGN, radio-SB, and AGN/SB (a mixture). We identified the presence of an active nucleus using the radio morphology, deviations from the radio/infrared correlation, and spatially resolved spectral index maps, and then correlated this to the usual mid-infrared ([NeV]/[NeII] and [OIV]/[NeII] line ratios and equivalent width of the 6.2um PAH feature) and optical (BPT diagram) AGN diagnostics. We find that 21 out of the 46 objects in our sample (~45%) are radio-AGN, 9 out of the 46 (~20%) are classified as starbursts (SB) based on the radio analysis, and 16 (~35%) are AGN/SB. After comparing to other AGN diagnostics we find 3 objects out of the 46 (~7%) that are identified as AGN based on the radio analysis, but are not classified as such based on the mid-infrared and optical AGN diagnostics presented in this study.
- ID:
- ivo://CDS.VizieR/J/A+A/555/A110
- Title:
- Radio images of CIZA J2242.8+5301
- Short Name:
- J/A+A/555/A110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Giant cluster radio relics are thought to form at shock fronts in the course of collisions between galaxy clusters. Via processes that are still poorly understood, these shocks accelerate or re-accelerate cosmic-ray electrons and might amplify magnetic fields. The best object to study this phenomenon is the galaxy cluster CIZA J2242.8+5301 as it shows the most undisturbed relic. By means of Giant Metrewave Radio Telescope (GMRT) and Westerbork Synthesis Radio Telescope (WSRT) data at seven frequencies spanning from 153MHz to 2272MHz, we study the synchrotron emission in this cluster. We aim at distinguishing between theoretical injection and acceleration models proposed for the formation of radio relics. We also study the head-tail radio sources to reveal the interplay between the merger and the cluster galaxies. We produced spectral index, curvature maps, and radio colour-colour plots and compared our data with predictions from models. We present one of the deepest 153MHz maps of a cluster ever produced, reaching a noise level of 1.5mJy/beam. We derive integrated spectra for four relics in the cluster, discovering extremely steep spectrum diffuse emission concentrated in multiple patches. We find a possible radio phoenix embedded in the relic to the south of the cluster. The spectral index of the northern relic retains signs of steepening from the front towards the back of the shock also at the radio frequencies below 600MHz. The spectral curvature in the same relic also increases in the downstream area. The data is consistent with the Komissarov-Gubanov injection models, meaning that the emission we observe is produced by a single burst of spectrally-aged accelerated radio electrons.
1347. Radio images of NGC 4631
- ID:
- ivo://CDS.VizieR/J/A+A/632/A11
- Title:
- Radio images of NGC 4631
- Short Name:
- J/A+A/632/A11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 4631 is an interacting galaxy which exhibits one of the largest gaseous halos observed among edge-on galaxies. We aim to examine the synchrotron and polarization properties of its disk and halo emission with new radio continuum data. Radio continuum observations of NGC 4631 were performed with the Karl G. Jansky Very Large Array at C-band (5.99GHz) in the C & D array configurations, and at L-band (1.57GHz) in the B, C, & D array configurations. The Rotation Measure Synthesis algorithm was utilized to derive the polarization properties. We detected linearly polarized emission at C-band and L-band. The magnetic field in the halo is characterized by strong vertical components above and below the central region of the galaxy. The magnetic field in the disk is only clearly seen in the eastern side of NGC 4631, where it is parallel to the plane of the major axis of the galaxy. We detected for the first time a large-scale, smooth Faraday depth pattern in a halo of an external spiral galaxy, which implies the existence of a regular (coherent) magnetic field. A quasi-periodic pattern in Faraday depth with field reversals was found in the northern halo of the galaxy. The field reversals in the northern halo of NGC 4631, together with the observed polarization angles, indicate giant magnetic ropes (GMRs) with alternating directions. To our knowledge, this is the first time such reversals are observed in an external galaxy.
- ID:
- ivo://CDS.VizieR/J/ApJ/701/1922
- Title:
- Radio interferometric planet search. I.
- Short Name:
- J/ApJ/701/1922
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Radio astrometry of nearby, low-mass stars has the potential to be a powerful tool for the discovery and characterization of planetary companions. We present a Very Large Array survey of 172 active M dwarfs at distances of less than 10pc. Twenty-nine stars were detected with flux densities greater than 100uJy. We observed seven of these stars with the Very Long Baseline Array at milliarcsecond resolution in three separate epochs. With a detection threshold of 500uJy in images of sensitivity 1{sigma}~100uJy, we detected three stars three times (GJ 65B, GJ 896A, GJ 4247), one star twice (GJ 285), and one star once (GJ 803). Two stars were undetected (GJ 412B and GJ 1224). For the four stars detected in multiple epochs, residuals from the optically determined apparent motions have an root-mean-square deviation of ~0.2 milliarcseconds, consistent with statistical noise limits. Combined with previous optical astrometry, these residuals provide acceleration upper limits that allow us to exclude planetary companions more massive than 3-6M_Jup_ at a distance of ~1AU with a 99% confidence level.
- ID:
- ivo://CDS.VizieR/J/A+A/575/A55
- Title:
- Radio jet emission from GeV-emitting NLSy1
- Short Name:
- J/A+A/575/A55
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- With the current study we aim at gaining understanding on the properties of radio emission and the assumed jet from four radio loud and {gamma}-ray loud Narrow Line Seyfert 1 galaxies i.e. Seyfert 1 galaxies with emission lines at the low-end of the FWHM distribution. The ultimate goal is twofold; first, the investigation whether a relativistic jet is operating at the source giving out the radio output observed and second, the quantification of the jet characteristics in order to understand possible similarities and differences with the jets found in typical blazars. The current study relies on the most systematic monitoring of radio loud and {gamma}-ray detected Narrow Line Seyfert 1 galaxies in the cm and mm radio bands conducted with the Effelsberg 100-m and IRAM 30-m telescopes. It covers the longest time baselines and the most radio frequencies, to date. This dataset of multi- wavelength, long-term radio light curves is analysed from a number of perspectives. A novel algorithm is introduced in order to extract sensible variability parameters (mainly amplitudes and timescales) which are then used for the computation of variability brightness temperatures and the corresponding Doppler factors. The jet powers are computed from the light curves to estimate the energy output and compare it with typical blazars. The dynamics of radio Spectra Energy Distributions are examined for understanding the mechanism causing the variability. The length of the available light curves for 3 of the 4 sources in the sample allowed a firm understanding of the general behaviour of the sources. They all display intensive variability which seems to be happening at a pace rather faster than what is generally seen in blazars. The flaring events become progressively more prominent as the frequency increases and show intensive spectral evolution indicative of shock evolution. The variability brightness temperatures and the associated Doppler factors are rather moderate implying a mildly relativistic jet. The computed jet powers show very energetic flows. The radio polarisation in one case, clearly implies the presence of a quiescent jet underlying recursive flaring activity. Finally, in one case, the sudden disappearance of a {gamma}-ray flare below some critical frequency in our band, urges for further investigation of the possible mechanism causing the evolution of broadband events. Despite the generally lower flux densities the sources appear to show all typical characteristics seen in blazars powered by relativistic jets. Intensive variability, spectral evolution across the different bands following evolutionary paths explained by traveling shocks, Doppler factors indicating mildly relativistic speeds.
- ID:
- ivo://CDS.VizieR/J/MNRAS/461/2346
- Title:
- Radio-loud and radio-quiet quasars sample
- Short Name:
- J/MNRAS/461/2346
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We compare covering factors of circumnuclear dusty obscurers in radio-loud and radio-quiet quasars. The radio-loud quasars are represented by a sample of FR II quasars obtained by cross-matching a catalog of the FR II radio sources selected by van Velzen et al. with the SDSS DR7 catalog of quasars. Covering factors of FR II quasars are compared with covering factors of the radio-quiet quasars matched with them in redshift, black hole mass, and Eddington-ratio. We found that covering factors, proxied by the infrared-to-bolometric luminosity ratio, are on average slightly smaller in FR II quasars than in radio-quiet quasars, however, this difference is statistically significant only for the highest Eddington ratios. For both samples, no statistically significant dependence of a median covering factor on Eddington ratio, black hole mass, nor redshift can be claimed.
