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961. VLBI images of 2 binary AGN candidates
ID:
ivo://CDS.VizieR/J/A+A/588/A102
Title:
VLBI images of 2 binary AGN candidates
Short Name:
J/A+A/588/A102
Date:
21 Oct 2021
Publisher:
CDS
Description:
The sources SDSS J113126.08-020459.2 and SDSS J110851.04+065901.4 are two double-peaked [OIII] emitting AGN, identified as candidate binary AGNs by optical and near infrared (NIR) observations. We observed the two sources with high resolution Very Long Baseline Interferometry (VLBI) using the European VLBI Network at 5GHz, reduced VLA observations at three frequencies available for one of the sources, and used archival HST observations. For the source SDSS J113126.08-020459.2, the VLBI observations detected only one single compact component associated with the eastern NIR nucleus. In SDSS J110851.04+065901.4, the VLBI observations did not detect any compact components, but the VLA observations allowed us to identify a possible compact core in the region of the north-western optical/NIR nucleus. In this source we find kpc-scale extended radio emission that is spatially coincident to the ultraviolet continuum and to the extended emission narrow line region. The UV continuum is significantly obscured since the amount of extended radio emission yields a star formation rate of about 110M_{sun}_/yr, which is an order of magnitude larger than implied by the observed ultraviolet emission. Our analysis confirms the presence of only one AGN in the two candidate binary AGNs.
962. VLBI imaging of 105 extragalactic radio sources
ID:
ivo://CDS.VizieR/J/A+A/526/A102
Title:
VLBI imaging of 105 extragalactic radio sources
Short Name:
J/A+A/526/A102
Date:
21 Oct 2021
Publisher:
CDS
Description:
The European space astrometry mission Gaia, to be launched by 2012, will construct a dense optical QSO-based celestial reference frame which will need to be linked to the International Celestial Reference Frame (ICRF; the IAU fundamental frame), with the highest accuracy. However, it has been found that only 10% of the ICRF sources (70 sources) are suitable to establish this link. The remaining sources are not useful either because they are not bright enough at optical wavelengths or because they have significant extended radio emission which precludes reaching the highest astrometric accuracy. In order to improve the accuracy of this alignment, we have developed a program of VLBI observations based on three steps to detect, image and measure astrometric positions of weak extragalactic radio sources, with bright optical counterparts, from a sample of 447 candidate sources. The experiments devoted to VLBI detection, carried out with the European VLBI Network (EVN) in June and October 2007, were very successful, with 398 sources detected at both S- and X-bands. From these, 105 sources were observed in March 2008 with a global VLBI array (EVN and VLBA; Very Long Baseline Array) for imaging their VLBI structures. All sources were successfully imaged in both bands and about 50% (47 sources) were found to be point-like on VLBI scales. These images are available at http://www.obs.u-bordeaux1.fr/BVID/GC030/. VLBI positions of these sources will be measured accurately in future astrometric experiments.
963. VLBI monitoring of NGC 4258
ID:
ivo://CDS.VizieR/J/ApJ/659/1040
Title:
VLBI monitoring of NGC 4258
Short Name:
J/ApJ/659/1040
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report a 3yr, 18 epoch, VLBI monitoring study of H_2_O masers in the subparsec, warped, accretion disk within the NGC 4258 AGN. Our immediate goals are to trace the geometry of the underlying disk, track rotation via measurement of proper motion, and ascertain the radii of masers for which centripetal acceleration may be measured separately. The monitoring includes 4 times as many epochs, 3 times denser sampling, and tighter control over sources of systematic error than earlier VLBI investigations. Coverage of a 2400km/s bandwidth has also enabled mapping of molecular material 30% closer to the black hole than accomplished previously, which will strengthen geometric and dynamical disk models. Through repeated observation we have also measured for the first time a 5uas (1sigma) thickness of the maser medium.
964. VLTI/MIDI AGN Large Program observations
ID:
ivo://CDS.VizieR/J/A+A/558/A149
Title:
VLTI/MIDI AGN Large Program observations
Short Name:
J/A+A/558/A149
Date:
21 Oct 2021
Publisher:
CDS
Description:
The AGN-heated dust distribution (the "torus") is increasingly recognized not only as the absorber required in unifying models, but as a tracer for the reservoir that feeds the nuclear Super-Massive Black Hole. Yet, even its most basic structural properties (such as its extent, geometry and elongation) are unknown for all but a few archetypal objects. In order to understand how the properties of AGN tori are related to feeding and obscuration, we need to resolve the matter distribution on parsec scales. Since most AGNs are unresolved in the mid-infrared, even with the largest telescopes, we utilize the MID-infrared interferometric Instrument (MIDI) at the Very Large Telescope Interferometer (VLTI) that is sensitive to structures as small as a few milli-arcseconds (mas). We present here an extensive amount of new interferometric observations from the MIDI AGN Large Program (2009-2011) and add data from the archive to give a complete view of the existing MIDI observations of AGNs. Additionally, we have obtained high-quality mid-infrared spectra from VLT/VISIR to provide a precise total flux reference for the interferometric data. We present correlated and total fluxes for 23 AGNs (16 of which with new data) and derive flux and size estimates at 12m using simple axisymmetric geometrical models.
965. VRI and K-band light curves of type 1 AGNs
ID:
ivo://CDS.VizieR/J/ApJ/886/150
Title:
VRI and K-band light curves of type 1 AGNs
Short Name:
J/ApJ/886/150
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of a dust-reverberation survey of quasars at redshifts z<0.6. We found a delayed response of the K-band flux variation after the optical flux variation in 25 out of 31 targets, and obtained the lag time between them for 22 targets. Combined with the results for nearby Seyfert galaxies, we provide the largest homogeneous collection of K-band dust-reverberation data for 36 type 1 active galactic nuclei (AGNs). This doubles the sample and includes the most distant AGN and the largest lag so far measured. We estimated the optical luminosity of the AGN component of each target using three different methods: spectral decomposition, the flux-variation-gradient method, and image decomposition. We found a strong correlation between the reverberation radius for the innermost dust torus and the optical luminosity over a range of approximately four orders of magnitude in luminosity, as is already known for Seyfert galaxies. We estimated the luminosity distances of the AGNs based on their dust-reverberation lags, and found that the data in the redshift-distance diagram are consistent with the current standard estimates of the cosmological parameters. We also present the radius-luminosity relations for isotropic luminosity indicators such as the hard X-ray (14-195keV), [OIV]25.89{mu}m, and mid-infrared (12{mu}m) continuum luminosities, which are applicable to obscured AGNs.
966. VSOP 5 GHz AGN Survey
ID:
ivo://CDS.VizieR/J/PASJ/52/997
Title:
VSOP 5 GHz AGN Survey
Short Name:
J/PASJ/52/997
Date:
21 Oct 2021
Publisher:
CDS
Description:
The VSOP mission is a Japanese-led project to image radio sources with sub-milliarcsec resolution by correlating the signal from the orbiting 8-m telescope, HALCA, with a global array of telescopes. Twenty- five percent of the scientific time of this mission is devoted to a survey of 402 bright, small-diameter extra-galactic radio sources at 5-GHz. The major goals of the VSOP Survey are statistical in nature: to determine the brightness temperature and approximate structure; to provide a source list for use with future space VLBI missions; and to compare radio properties with other data throughout the EM spectrum. This paper describes: the compilation of a complete list of radio sources associated with active galactic nuclei (AGN); the selection of the subsample of sources to be observed with VSOP; the extensive ground resources used for the Survey; the status of the observations as of 2000 July; the data-analysis methods; and several examples of results from the VSOP Survey. More detailed results from the full sample will be given in future papers.
967. VSOP 5 GHz AGN Survey. III
ID:
ivo://CDS.VizieR/J/ApJS/155/33
Title:
VSOP 5 GHz AGN Survey. III
Short Name:
J/ApJS/155/33
Date:
21 Oct 2021
Publisher:
CDS
Description:
The VLBI Space Observatory Programme (VSOP) mission is a Japanese-led project to study radio sources with sub-milliarcsec resolution using an orbiting 8m telescope, HALCA, along with global arrays of Earth-based telescopes. Approximately 25% of the observing time is devoted to a survey of compact active galactic nuclei (AGNs) that are stronger than 1Jy at 5GHz - the VSOP AGN Survey. This paper, the third in the series, presents the results from the analysis of the first 102 Survey sources.
968. VSOP 5GHz AGN Survey. IV
ID:
ivo://CDS.VizieR/J/ApJ/616/110
Title:
VSOP 5GHz AGN Survey. IV
Short Name:
J/ApJ/616/110
Date:
21 Oct 2021
Publisher:
CDS
Description:
The VLBI Space Observatory Programme (VSOP) mission is a Japanese-led project to study radio sources with submilliarcsecond angular resolution, using an orbiting 8m telescope on board the satellite HALCA with a global Earth-based array of telescopes. A major program is the 5GHz VSOP Survey Program, which we supplement here with Very Long Baseline Array observations to produce a complete and flux density-limited sample. Using statistical methods of analysis of the observed visibility amplitude versus projected (u, v) spacing, we have determined the angular size and brightness temperature distribution of bright radio emission from active galactic nuclei.
969. VSOP 5GHz AGN survey V.
ID:
ivo://CDS.VizieR/J/ApJS/175/314
Title:
VSOP 5GHz AGN survey V.
Short Name:
J/ApJS/175/314
Date:
21 Oct 2021
Publisher:
CDS
Description:
In 1997 February, the Japanese radio astronomy satellite HALCA was launched to provide the space-bourne element for the VLBI Space Observatory Program (VSOP) mission. Approximately 25% of the mission time was dedicated to the VSOP survey of bright compact active galactic nuclei (AGNs) at 5GHz. This paper, the fifth in the series, presents images and models for the remaining 140 sources not included in the third paper in the series, which contained 102 sources. For most sources, the plots of the (u,v) coverage, the visibility amplitude versus (u,v) distance, and the high-resolution image are presented. Model fit parameters to the major radio components are determined, and the brightness temperature of the core component for each source is calculated. The brightness temperature distributions for all of the sources in the VSOP AGN survey are discussed.
970. Warm IRAS sources. I. AGN candidates
ID:
ivo://CDS.VizieR/J/A+AS/70/95
Title:
Warm IRAS sources. I. AGN candidates
Short Name:
J/A+AS/70/95
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have previously shown that a blue (warm) 60 to 25{mu}m infrared colour provides a powerful parameter for discriminating between AGNs and normal galaxies and that the far-IR spectrum is therefore an efficient tool for finding new AGNs (de Grijp et al., 1985Natur.314..140D) Here we present a list of such AGN candidates based on warm IR sources from the IRAS Point Source Catalogue (PSC, Cat. II/125). Identification data and finding charts are also given. In addition the list of warm IRAS sources is supplemented by a compendium of data from the IRAS PSC on detected sources identified with previously known AGNs whose infrared spectra do not bring them within our colour selection criterion