- ID:
- ivo://CDS.VizieR/J/ApJS/243/21
- Title:
- A complete sample of broad-line AGN from SDSS-DR7
- Short Name:
- J/ApJS/243/21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A new, complete sample of 14584 broad-line active galactic nuclei (AGNs) at z<0.35 is presented, which are uncovered homogeneously from the complete database of galaxies and quasars observed spectroscopically in the Sloan Digital Sky Survey Seventh Data Release. The stellar continuum is properly removed for each spectrum with significant host absorption line features, and careful analyses of the emission line spectra, particularly in the H{alpha} and H{beta} wavebands, are carried out. The broad Balmer emission line, particularly H{alpha}, is used to indicate the presence of an AGN. The broad H{alpha} lines have luminosities in a range of 10^38.5^-10^44.3^erg/s, and line widths (FWHMs) of 500-34000km/s. The virial black hole masses, estimated from the broad-line measurements, span a range of 10^5.1^-10^10.3^M_{sun}_, and the Eddington ratios vary from -3.3 to 1.3 in logarithmic scale. Other quantities such as multiwavelength photometric properties and flags denoting peculiar line profiles are also included in this catalog. We describe the construction of this catalog and briefly discuss its properties. The catalog is publicly available online. This homogeneously selected AGN catalog, along with the accurately measured spectral parameters, provides the most updated, largest AGN sample data, which will enable further comprehensive investigations of the properties of the AGN population in the low-redshift universe.
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- ID:
- ivo://CDS.VizieR/J/other/Ap/63.322
- Title:
- Activity type of AGN with SDSS spectra
- Short Name:
- J/other/Ap/63.32
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is a detailed spectral classification of 96 active galaxies from the Veron-Cetty and Veron catalog (2010, Version 13, Cat. VII/258) of active galaxies and quasars. These objects were identified as radio sources using standard radio catalogs. Those galaxies which had radio sources in at least 6 different radio bands and had been identified spectrally in the SDSS catalog were selected. The types of activity of these were determined using their SDSS spectra. Three diagnostic diagrams and a direct study of the spectra were used for more certain classification. As a result, the classifications of 85% of the objects were changed. The radio sources in different radio bands make it possible to construct the spectral distribution of the energy in the radio range and to compare it with the optical activity types.
- ID:
- ivo://CDS.VizieR/J/other/Ap/62.147
- Title:
- Activity types of ROSAT/SDSS galaxies
- Short Name:
- J/other/Ap/62.14
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this study we carry out detailed spectral classification of 173 AGN candidates from the Joint HRC/BHRC sample, which is a combination of HRC (Hamburg-ROSAT Catalogue) and BHRC (Byurakan-Hamburg-ROSAT Catalogue). These objects were revealed as optical counterparts for ROSAT X-ray sources, however spectra for 173 of them are given in SDSS without definite spectral classification. We studied these 173 objects using the SDSS spectra and revealed the detailed activity types for them. Three diagnostic diagrams and direct examination of the spectra were used to have more confident classification. We also made identification of these sources in other wavelength ranges and calculated some of their parameters.
- ID:
- ivo://CDS.VizieR/J/ApJ/701/535
- Title:
- A sample of candidate radio stars
- Short Name:
- J/ApJ/701/535
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We conduct a search for radio stars by combining radio and optical data from the FIRST survey (Cat. VIII/71) and the Sloan Digital Sky Survey (SDSS-DR6, Cat. II/282, obsoleted by II/294). The faint limit of SDSS makes possible a homogeneous search for radio emission from stars of low optical luminosity. We select a sample of 112 candidate radio stars in the magnitude range 15<i<~19.1 and with radio flux S_20_>=1.25mJy, from about 7000deg^2^ of sky. The selection criteria are positional coincidence within 1", radio and optical point source morphology, and an SDSS spectrum classified as stellar. The sample contamination is estimated by random matching to be 108+/-13, suggesting that at most a small fraction of the selected candidates are genuine radio stars. Therefore, we rule out a very rare population of extremely radio-loud stars: no more than 1.2 of every million stars in the magnitude range 15<i<19.1 stars has radio flux S_20_>=1.25mJy. We investigate the optical and radio colors of the sample to find candidates that show the largest likelihood of being real radio stars. The significant outliers from the stellar locus, as well as the magnetically active stars, are the best candidates for follow-up radio observations.
- ID:
- ivo://CDS.VizieR/J/ApJ/858/65
- Title:
- A VLA study of high-redshift GRBs. I. GRB140311A
- Short Name:
- J/ApJ/858/65
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first results from a recently concluded study of GRBs at z>~5 with the Karl G. Jansky Very Large Array (VLA). Spanning 1 to 85.5GHz and 7 epochs from 1.5 to 82.3d, our observations of GRB140311A are the most detailed joint radio and millimeter observations of a GRB afterglow at z>~5 to date. In conjunction with optical/near-IR and X-ray data, the observations can be understood in the framework of radiation from a single blast wave shock with energy E_K,iso_~8.5x10^53^erg expanding into a constant density environment with density, n_0_~8cm^-3^. The X-ray and radio observations require a jet break at t_jet_~0.6d, yielding an opening angle of {theta}_jet_~4{deg} and a beaming-corrected blast wave kinetic energy of E_K_~2.2x10^50^erg. The results from our radio follow-up and multiwavelength modeling lend credence to the hypothesis that detected high-redshift GRBs may be more tightly beamed than events at lower redshift. We do not find compelling evidence for reverse shock emission, which may be related to fast cooling driven by the moderately high circumburst density.
- ID:
- ivo://CDS.VizieR/J/AZh/79/675
- Title:
- B-band photometry of BL Lac object ON 231
- Short Name:
- J/AZh/79/675
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of 19-year optical monitoring of ON 231 are presented. Photographic B-band observations were obtained during 123 nights from April 1972 to March 1990 as part of the quasar monitoring program carried out the Astronomical Institute of St. Petersburg State University.
- ID:
- ivo://CDS.VizieR/J/ApJ/799/72
- Title:
- Binary AGNs from the VLA Stripe 82 survey
- Short Name:
- J/ApJ/799/72
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Galaxy mergers play an important role in the growth of galaxies and their supermassive black holes. Simulations suggest that tidal interactions could enhance black hole accretion, which can be tested by the fraction of binary active galactic nuclei (AGNs) among galaxy mergers. However, determining the fraction requires a statistical sample of binaries. We have identified kiloparsec-scale binary AGNs directly from high-resolution radio imaging. Inside the 92deg^2^ covered by the high-resolution Very Large Array survey of the Sloan Digital Sky Survey (SDSS) Stripe 82 field, we identified 22 grade A and 30 grade B candidates of binary radio AGNs with angular separations less than 5" (10kpc at z=0.1). Eight of the candidates have optical spectra for both components from the SDSS spectroscopic surveys and our Keck program. Two grade B candidates are projected pairs, but the remaining six candidates are all compelling cases of binary AGNs based on either emission line ratios or the excess in radio power compared to the H{alpha}-traced star formation rate. Only two of the six binaries were previously discovered by an optical spectroscopic search. Based on these results, we estimate that ~60% of our binary candidates would be confirmed once we obtain complete spectroscopic information. We conclude that wide-area high-resolution radio surveys offer an efficient method to identify large samples of binary AGNs. These radio-selected binary AGNs complement binaries identified at other wavelengths and are useful for understanding the triggering mechanisms of black hole accretion.
- ID:
- ivo://CDS.VizieR/J/ApJ/867/131
- Title:
- Blazar candidates behind the Magellanic Clouds
- Short Name:
- J/ApJ/867/131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the identification of blazar candidates behind the Magellanic Clouds. The objects were selected from the Magellanic Quasars Survey (MQS), which targeted the entire Large Magellanic Cloud (LMC) and 70% of the Small Magellanic Cloud (SMC). Among the 758 MQS quasars and 898 of the unidentified (featureless spectra) objects, we identified a sample of 44 blazar candidates, including 27 flat-spectrum radio quasars and 17 BL Lacertae objects, respectively. All the blazar candidates from our sample were identified with respect to their radio, optical, and midinfrared properties. The newly selected blazar candidates possess the long-term, multicolor photometric data from the Optical Gravitational Lensing Experiment, multicolor midinfrared observations, and archival radio data for one frequency at least. In addition, for nine of them, the radio polarization data are available. With such data, these objects can be used to study the physics behind the blazar variability detected in the optical and midinfrared bands, as a tool to investigate magnetic field geometry of the LMC and SMC, and as an exemplary sample of point-like sources most likely detectable in the {gamma}-ray range with the newly emerging Cherenkov Telescope Array.
- ID:
- ivo://CDS.VizieR/J/AJ/129/2542
- Title:
- BL Lac from SDSS
- Short Name:
- J/AJ/129/2542
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a sample of 386 BL Lacertae candidates identified from 2860deg^2^ of the Sloan Digital Sky Survey (SDSS) spectroscopic database. The candidates are primarily selected to have quasi-featureless optical spectra and low proper motions as measured from SDSS and USNO-B positions; however, our ability to separate Galactic from extragalactic quasi-featureless objects (QFOs) on the basis of proper motion alone is limited by the lack of reliable proper motion measurements for faint objects. Based largely on this remarkably clean color separation, we subdivide the sample into 240 probable candidates and 146 additional less probable (likely stellar) candidates.
- ID:
- ivo://CDS.VizieR/J/MNRAS/204/151
- Title:
- Bright radio sources at 178 MHz (3CRR)
- Short Name:
- J/MNRAS/204/151
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A revised sample of bright radio sources at 178MHz is defined in order to correct the biases introduced into the 3CR catalog by confusion and partial resolution. The sample is shown to be 96 percent complete to a flux-density limit of 10Jy for sources smaller than 10arcmin. The bias of the 3CR catalog against objects of larger angular size is also reduced. Optical identifications are presented for 96 percent of the sources, 71 percent with galaxies and 25 percent with quasars. The radio-galaxy population is found to show strong space-density evolution for luminosities in excess of approximately 10^26.5^W/Hz/sr at 178MHz (redshifts greater than or approximately equal to 0.2), while the evolutionary properties of galaxies and quasars of the same luminosity and redshift are very similar.