- ID:
- ivo://CDS.VizieR/J/A+A/356/445
- Title:
- ROSAT-FIRST AGN correlation
- Short Name:
- J/A+A/356/445
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a correlation of the ROSAT All-Sky Survey with the April 1997 release of the VLA 20cm FIRST (Cat. <VIII/59>) catalogue. We focus our analysis on the 843 X-ray sources which have unique radio counterparts. The majority of these objects (84%) have optical counterparts on the POSS 1 plates. Approximately 30% have been previously classified and we obtain new spectroscopic classifications for 85 sources by comparison with the ongoing FIRST Bright Quasar Survey and 106 additional sources from our own new spectroscopic data. Approximately 51% of the sources are presently classified, and the majority of the unclassified objects are optically faint. The newly classified sources are generally radio weak, exhibiting properties intermediate with previous samples of radio- and X-ray-selected AGN. This also holds for the subsample of 71 BL Lacs which includes many intermediate objects. The 146 quasars show no evidence for a bimodal distribution in their radio-loudness parameter, indicating that the supposed division between radio-quiet and radio-loud AGN may not be real. The X-ray and radio luminosities are correlated over two decades in radio luminosity, spanning the radio-loud and radio-quiet regimes, with radio-quiet quasars showing a linear correlation between the two luminosities. Many of the sources show peculiar or unusual properties which call for more detailed follow-up observations. We also give the X-ray and radio data for the 518 X-ray sources for which more than one radio object is found. Because of the difficulties inherent in identifying optical counterparts to these complex sources, we do not consider these data in the current analysis.
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Search Results
162. Sample of 966 AGNs
- ID:
- ivo://CDS.VizieR/J/other/RAA/20.25
- Title:
- Sample of 966 AGNs
- Short Name:
- J/other/RAA/20.2
- Date:
- 03 Dec 2021 00:39:07
- Publisher:
- CDS
- Description:
- Active galactic nuclei (AGNs) can be divided into two major classes, namely radio-loud and radio-quiet AGNs. A small subset of the radio-loud AGNs is called blazars, which are believed to be unified with Fanaroff-Riley type I and type II (FRI&II) radio galaxies. Following our previous work, we present a latest sample of 966 sources with measured radio flux densities of the core and extended components. The sample includes 83 BL Lacs, 473 flat spectrum radio quasars, 101 Seyferts, 245 galaxies, 52 FRIs&IIs and 12 unidentified sources. We then calculate the radio core-dominance parameters and spectral indices and study their relationship. Our analysis shows that the core-dominance parameters and spectral indices are quite different for different types of sources. We also confirm that the correlation between core-dominance parameter and radio spectral index extends over all the sources in a large sample presented.
163. Sample of 2400 AGNs
- ID:
- ivo://CDS.VizieR/J/other/RAA/19.70
- Title:
- Sample of 2400 AGNs
- Short Name:
- J/other/RAA/19.7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Active galactic nuclei (AGNs) can be divided into two major classes, namely radio-loud and radio-quiet AGNs. A small subset of the radio-loud AGNs is called blazars, which are believed to be unified with Fanaroff-Riley type I/II (FRI/II) radio galaxies. Following our previous work (Fan et al., 2011RAA....11.1413F), we present a sample of 2400 sources with measured radio flux densities of the core and extended components. The sample contains 250 BL Lacs, 520 quasars, 175 Seyferts, 1178 galaxies, 153 FRI or FRII galaxies and 104 unidentified sources. We then calculate the radio core-dominance parameters and spectral indices, and study their relationship. Our analysis shows that the core-dominance parameters and spectral indices are quite different for different types of sources. We also confirm that the correlation between core-dominance parameter and spectral index exists for a large sample presented in this work.
- ID:
- ivo://CDS.VizieR/J/other/AstBu/70.264
- Title:
- Sample of 877 blazars
- Short Name:
- J/other/AstBu/70
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the synchrotron component of the spectral energy distribution on the sample of 877 blazars using ASDC SED Builder Tool with available broadband data from the literature. Our sample includes 423 flat-spectrum radio sources (FSRQs), 361 BL Lac objects and candidates, and 93 blazars of uncertain type. We have made an estimation of the synchrotron peak frequency for the 875 objects and further classified them as high, intermediate and low synchrotron peaked sources (HSPs/ISPs/LSPs). For each source NVSS name (RA (HHMMSS) and DEC (DDMMSS) for the J2000.0 epoch), alias, redshift, R band magnitude, synchrotron peak frequency, correlation coefficient, flux density at 4.8GHz, SED class, blazar type and selection method are presented.
- ID:
- ivo://CDS.VizieR/J/other/AstBu/68.262
- Title:
- Sample of 467 GPS candidates
- Short Name:
- J/other/AstBu/68
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of a comprehensive analysis of continuous radio spectra of a sample of Gigahertz-Peaked Spectrum (GPS) sources are reported. The sources are selected from a flux-density-complete sample (S more or equal 200mJy at 4.8 or 5GHz) using multifrequency measurements of the RATAN-600 radio telescope and data from the CATS astrophysical catalogs support system. The analysis revealed a very small number (1-2%) of "classical" GPS objects, which is significantly less than the expected fraction of 10%. GPS galaxies are found to have narrower and steeper radio spectra than quasars. The low-frequency part of the spectrum is seen to become steeper with increasing redshift. Galaxies and quasars at the same z have comparable angular sizes, whereas their luminosities may differ by one order of magnitude. At large redshifts there is a deficit of objects with low (several GHz) peak frequencies. The number of GPS galaxies decreases sharply with redshift, and most of them are found at z between 0.01 and 1.81. GPS quasars are found at large redshifts, from 0.11 to 3.99. A quarter of the sample consists of blazars whose spectra may temporarily have a convex shape when the object is in active state.
- ID:
- ivo://CDS.VizieR/J/A+A/577/A36
- Title:
- Sample of weak blazars at mas resolution
- Short Name:
- J/A+A/577/A36
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We started a follow-up investigation of the "Deep X-ray Radio Blazar Survey" objects with declination >-10{deg} to better understand the blazar phenomenon. We undertook a survey with the European Very Long Baseline Interferometry Network at 5GHz to make the first images of a complete sample of weak blazars, aiming at a follow-up comparison between high- and low-power samples of blazars. We observed 87 sources with the EVN at 5GHz during the period October 2009 to May 2013. The observations were correlated at the Max-Planck-Institut fuer Radioastronomie and at the Joint Institute for VLBI in Europe. The correlator output was analysed using both the AIPS and DIFMAP software packages. All of the sources observed were detected. Point-like sources are found in 39 cases on a milli-arcsecond scale, and 48 show core-jet structure. The total flux density distribution at 5GHz has a median value <S>=44^+23^_-10_mJy. A total flux density <=150mJy is observed in 68 out of 87 sources. Their brightness temperature T_b_ ranges between 10^7^K and 10^12^K. According to the spectral indices previously obtained with multi-frequency observations, 58 sources show a flat spectral index, and 29 sources show a steep spectrum or a spectrum peaking at a frequency around 1-2GHz. Adding to the DXRBS objects we observed those already observed with ATCA in the Southern sky, we found that 14 blazars and a Steep Spectrum Radio Quasars, are associated to {gamma}-ray emitters. We found that 56 sources can be considered blazars. We also detected 2 flat spectrum narrow line radio galaxies. About 50% of the blazars associated to a {gamma}-ray object are BLLacs, confirming that they are more likely detected among blazars {gamma}-emitters. We confirm the correlation found between the source core flux density and the {gamma}-ray photon fluxes down to fainter flux densities. We also found that weak blazars are also weaker {gamma}-ray emitters compared to bright blazars. Twenty-two sources are SSRQs or Compact Steep-spectrum Sources, and 7 are GigaHz Peaked Sources. The available X-ray ROSAT observations allow us to suggest that CSS and GPS quasars are not obscured by large column of cold gas surrounding the nuclei. We did not find any significant difference in X-ray luminosity between CSS and GPS quasars.
- ID:
- ivo://CDS.VizieR/J/ApJ/756/29
- Title:
- Scintillation of AGNs observed with the VLA
- Short Name:
- J/ApJ/756/29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The fraction of compact active galactic nuclei (AGNs) that exhibit interstellar scintillation (ISS) at radio wavelengths, as well as their scintillation amplitudes, have been found to decrease significantly for sources at redshifts z>~2. This can be attributed to an increase in the angular sizes of the {mu}as-scale cores or a decrease in the flux densities of the compact {mu}as cores relative to that of the mas-scale components with increasing redshift, possibly arising from (1) the space-time curvature of an expanding universe, (2) AGN evolution, (3) source selection biases, (4) scatter broadening in the ionized intergalactic medium (IGM) and intervening galaxies, or (5) gravitational lensing. We examine the frequency scaling of this redshift dependence of ISS to determine its origin, using data from a dual-frequency survey of ISS of 128 sources at 0<~z<~4. We present a novel method of analysis which accounts for selection effects in the source sample.
- ID:
- ivo://CDS.VizieR/J/AJ/132/1475
- Title:
- SDSS AGN from ROSAT PSPC
- Short Name:
- J/AJ/132/1475
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a sample of 1744 type 1 active galactic nuclei (AGNs) from the Sloan Digital Sky Survey Data Release 4 (SDSS DR4) spectroscopic catalog with X-ray counterparts in the White-Giommi-Angelini Catalog (WGACAT) of ROSAT PSPC pointed observations. Of 1744 X-ray sources, 1410 (80.9%) are new AGN identifications. Of 4574 SDSS DR4 AGNs for which we found radio matches in the catalog of radio sources from the Faint Images of the Radio Sky at Twenty cm survey, 224 turned up in our sample of SDSS X-ray AGNs. The sample objects are given in a catalog that contains optical and X-ray parameters and supporting data, including redshifts; it also contains radio emission parameters where available. We illustrate the content of our catalog and its potential for AGN science by providing statistical relationships for the catalog data.
- 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.
- 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.