- ID:
- ivo://CDS.VizieR/J/A+A/630/A110
- Title:
- SDSS-FIRST quasar sample study
- Short Name:
- J/A+A/630/A110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- When can an active galactic nucleus (AGN) be considered radio-loud? Following the established view of the AGNs inner workings, an AGN is radio-loud if associated with relativistic ejections emitting a radio synchrotron spectrum (i.e., it is a "jetted" AGN). In this paper we exploit the AGN main sequence that offers a powerful tool to contextualize radio properties. If large samples of optically-selected quasars are considered, AGNs are identified as radio-loud if their Kellermann's radio loudness ratio R_K_>10. Our aims are to characterize the optical properties of different classes based on radioloudness within the main sequence and to test whether the condition R_K_>10 is sufficient for the identification of RL AGNs, since the origin of relatively strong radio emission may not be necessarily due to relativistic ejection. A sample of 355 quasars was selected by cross-correlating the FIRST survey with the SDSS DR14 quasar catalog. We classified the optical spectra according to their spectral types along the main sequence of quasars. For each spectral type, we distinguished compact and extended morphology (providing a FIRST-based atlas of radio maps in the latter case), and three classes of radio-loudness: detected (specific flux ratio in the g band and at 1.4GHz, R_K'_<10), intermediate (10R_K'_<70), and radio loud (R_K'_>=70). The analysis revealed systematic differences between radio-detected (i.e., radio-quiet), radio-intermediate, and radio-loud in each spectral type along the main sequence. We show that spectral bins that contain the extreme Population A sources have radio power compatible with emission by mechanisms ultimately due to star formation processes. Radio-loud sources of Population B are characteristically jetted. Their broad H{beta} profiles can be interpreted as due to a binary broad-line region. We suggest that RL Population B sources should be preferential targets for the search of black hole binaries, and present a sample of binary black hole AGN candidates. The validity of the Kellermann's criterion may be dependent on the source location along the quasar main sequence. The consideration of the MS trends allowed to distinguish between sources whose radio emission mechanisms is "jetted" from the ones where the mechanism is likely to be fundamentally different.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/716/866
- Title:
- SDSS search for binary AGN
- Short Name:
- J/ApJ/716/866
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present active galactic nuclei (AGNs) from the Sloan Digital Sky Survey (SDSS) having double-peaked profiles of [OIII]5007,4959 and other narrow emission lines, motivated by the prospect of finding candidate binary AGNs. These objects were identified by means of a visual examination of 21592 quasars at z<0.7 in SDSS Data Release 7 (DR7). Of the spectra with adequate signal-to-noise, 148 spectra exhibit a double-peaked [OIII] profile. Of these, 86 are Type 1 AGNs and 62 are Type 2 AGNs. Only two give the appearance of possibly being optically resolved double AGNs in the SDSS images, but many show close companions or signs of recent interaction. Radio-detected quasars are three times more likely to exhibit a double-peaked [OIII] profile than quasars with no detected radio flux, suggesting a role for jet interactions in producing the double-peaked profiles. Of the 66 broad-line (Type 1) AGNs that are undetected in the FIRST survey, 0.9% show double-peaked [OIII] profiles.
- ID:
- ivo://CDS.VizieR/J/MNRAS/460/4433
- Title:
- SDSS Stripe 82 VLA 1-2GHz survey
- Short Name:
- J/MNRAS/460/4433
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used the Karl G. Jansky Very Large Array to image ~100deg^2^ of SDSS Stripe 82 at 1-2GHz. The survey consists of 1026 snapshot observations of 2.5-min duration, using the hybrid CnB configuration. The survey has good sensitivity to diffuse, low surface brightness structures and extended radio emission, making it highly synergistic with existing 1.4GHz radio observations of the region. The principal data products are continuum images, with 16x10 arcsec resolution, and a catalogue containing 11782 point and Gaussian components resulting from fits to the thresholded Stokes-I brightness distribution, forming approximately 8948 unique radio sources. The typical effective 1{sigma} noise level is 88{mu}Jy/beam. Spectral index estimates are included, as derived from the 1GHz of instantaneous bandwidth. Astrometric and photometric accuracy are in excellent agreement with existing narrowband observations. A large-scale simulation is used to investigate clean bias, which we extend into the spectral domain. Clean bias remains an issue for snapshot surveys with the VLA, affecting our total intensity measurements at the ~1{sigma} level. Statistical spectral index measurements are in good agreement with existing measurements derived from matching separate surveys at two frequencies. At flux densities below ~35{sigma} the median in-band spectral index measurements begin to exhibit a bias towards flatness that is dependent on both flux density and the intrinsic spectral index. In-band spectral curvature measurements are likely to be unreliable for all but the very brightest components. Image products and catalogues are publicly available via an FTP server (ftp://ftp.atnf.csiro.au/pub/people/hey036/Stripe82).
- ID:
- ivo://CDS.VizieR/J/MNRAS/455/2551
- Title:
- SDSS/3XMM X-ray-selected LINERs
- Short Name:
- J/MNRAS/455/2551
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A sample of 576 X-ray-selected LINERs was constructed by combining data from the 3XMM-DR4 and SDSS-DR7 catalogues. The sample was used to investigate the fraction of galaxies hosting a LINER, finding that the fraction is a strong function of both stellar mass and black hole mass (increasing as f_LINER_{prop.to}M*^1.6+/-0.2^ and f_LINER_{propto}M_BH_^0.6+/-0.1^, respectively) and that it rises close to unity at the highest black hole masses and lowest X-ray luminosities. After obtaining radio flux densities from the FIRST survey, the sample was also used to investigate the Fundamental Plane of black hole activity - a scale-invariant relationship between black hole mass, X-ray luminosity and radio luminosity that is believed to hold across at least nine orders of magnitude of mass. There are key advantages in using only LINERs for the derivation as these are the counterparts of the 'low-hard' X-ray binaries for which the relationship is tightest. The Fundamental Plane was found to be log(L_R_/(erg/s)) = 0.65(+/-0.07)log(L_X_/(10^42^erg/s)) + 0.69(+/-0.10)log(M_BH_/10^8^M_{sun}_) + 38.35(+/-0.10). The scatter around the plane was 0.73+/-0.03dex, too large to suggest that the Fundamental Plane can be used as a tool to estimate black hole mass from the observables of X-ray and radio luminosity. The black hole mass scaling is sensitive to the slope of the mass - velocity dispersion relation and, in order to achieve consistency with X-ray binaries, the analysis favours a steep gradient for this relationship, as found in recent research.
- ID:
- ivo://CDS.VizieR/VI/151
- Title:
- Search for radio emission from giant exoplanets
- Short Name:
- VI/151
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The intensity of Jupiter's auroral radio emission quickly gave rise to the question whether a comparable coherent emission from the magnetosphere of an exoplanet could be detectable. An exoplanetary radio emission would have to be at least 1000 times more intense than Jupiter's emission to be detectable with current radio telescopes. Theoretical models suggest that, at least in certain cases, the radio emission of giant exoplanets may indeed reach the required intensity. At the same time, in order to generate such an emission, an exoplanet would have to have a sufficiently strong intrinsic planetary magnetic field. Extrasolar planets are indeed expected to have a planetary magnetic field, but to date, their magnetic field has never been detected. We will show that the most promising technique to observe exoplanetary magnetic fields is indeed to search for the planetary auroral radio emission. The detection of such an emission would thus constitute the first unambiguous detection of an exoplanetary magnetic field. We will review recent theoretical studies and discuss their results for the two main parameters, namely the maximum emission frequency and the intensity of the radio emission. The predicted values should allow the detection using modern low-frequency radio telescopes. We will present an ongoing observation program with the Low Frequency Array (LOFAR), which has the potential to detect exoplanetary radio emission.
- ID:
- ivo://CDS.VizieR/J/ApJS/95/345
- Title:
- Second Caltech-Jodrell Bank VLBI Survey. I.
- Short Name:
- J/ApJS/95/345
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We define the sample for the second Caltech-Jodrell Bank VLBI survey. This is a sample of 193 flat- or gigahertz-peaked-spectrum sources selected at 4850 MHz. This paper presents images of 91 sources with a resolution of ~1 mas, obtained using VLBI observations at 4992 MHz with a global array. The remaining images and the integrated radio spectra will be presented in a forthcoming paper by Henstock et al.
- ID:
- ivo://CDS.VizieR/J/ApJS/100/1
- Title:
- Second Caltech-Jodrell Bank VLBI Survey. II.
- Short Name:
- J/ApJS/100/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the second of two papers presenting the Second Caltech- Jodrell Bank VLBI survey (CJ2). The CJ2 sample consists of 193 flat- and gigahertz-peaked-spectrum sources selected at 4850 MHz. In this paper we present images of the remaining 102 sources with ~1 mas resolution, obtained using VLBI snapshot observations at 4992 MHz with a global array. We also present integrated radio spectra for the entire CJ2 sample.
- ID:
- ivo://CDS.VizieR/J/AJ/151/154
- Title:
- Second epoch VLBA Calibrator Survey (VCS-II)
- Short Name:
- J/AJ/151/154
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Six very successful Very Long Baseline Array (VLBA) calibrator survey campaigns were run between 1994 and 2007 to build up a large list of compact radio sources with positions precise enough for use as very long baseline interferometry (VLBI) phase reference calibrators. We report on the results of a second epoch VLBA Calibrator Survey campaign (VCS-II) in which 2400 VCS sources were re-observed in the X and S bands in order to improve the upcoming third realization of the International Celestial Reference Frame (ICRF3) as well as to improve their usefulness as VLBI phase reference calibrators. In this survey, some 2062 previously detected sources and 324 previously undetected sources were detected and revised positions are presented. Average position uncertainties for the re-observed sources were reduced from 1.14 and 1.98mas to 0.24 and 0.41mas in R.A. and decl., respectively, or by nearly a factor of 5. Minimum detected flux values were approximately 15 and 28mJy in the X and S bands, respectively, and median total fluxes are approximately 230 and 280mJy. The vast majority of these sources are flat-spectrum sources, with ~82% having spectral indices greater than -0.5.
- ID:
- ivo://CDS.VizieR/J/AJ/126/2562
- Title:
- Second VLBA calibrator survey: VCS2
- Short Name:
- J/AJ/126/2562
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents an extension of the Very Long Baseline Array Calibrator Survey, called VCS2, containing 276 sources. This survey fills in regions of the sky that were not completely covered by the previous VCS1 calibrator survey. The VCS2 survey includes calibrator sources near the Galactic plane, -30{deg}<DE<-45{deg}, and VLA calibrators. The positions have been derived from astrometric analysis of the group delays measured at 2.3 and 8.4 GHz using the Goddard Space Flight Center CALC/SOLVE package. From the VLBA snapshot observations, images of the calibrators are available, and each source is given a quality code for anticipated use. The VCS2 catalog is available from the NRAO Web site.
- ID:
- ivo://CDS.VizieR/J/ApJ/716/30
- Title:
- SED of Fermi bright blazars
- Short Name:
- J/ApJ/716/30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have conducted a detailed investigation of the broadband spectral properties of the {gamma}-ray selected blazars of the Fermi LAT Bright AGN Sample (LBAS, Cat. J/ApJ/700/597). By combining our accurately estimated Fermi {gamma}-ray spectra with Swift, radio, infra-red, optical, and other hard X-ray/{gamma}-ray data, collected within 3 months of the LBAS data taking period, we were able to assemble high-quality and quasi-simultaneous spectral energy distributions (SED) for 48 LBAS blazars. We have used these SED to characterize the peak intensity of both the low- and the high-energy components. The results have been used to derive empirical relationships that estimate the position of the two peaks from the broadband colors (i.e., the radio to optical, {alpha}_ro_, and optical to X-ray, {alpha}_ox_, spectral slopes) and from the {gamma}-ray spectral index. While more than 50% of known radio bright high energy peaked (HBL) BL Lacs are detected in the LBAS sample, only less than 13% of known bright broad-lined flat spectrum radio quasars (FSRQs) and LBL BL Lacs are included. This suggests that the latter sources, as a class, may be much fainter {gamma}-ray emitters than LBAS blazars, and could in fact radiate close to the expectations of simple synchrotron self-Compton (SSC) models. We categorized all our sources according to a new physical classification scheme based on the generally accepted paradigm for Active Galactic Nuclei and on the results of this SED study.
