The Demise of the Classical Broad-Line Region in the Luminous Quasar PG 1416−129 (original) (raw)
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Investigating the radio-loud phase of broad absorption line quasars
Astronomy & Astrophysics, 2014
Context. Broad absorption lines (BALs) are present in the spectra of ⇠20% of quasars (QSOs); this indicates fast outflows (up to 0.2c) that intercept the observer's line of sight. These QSOs can be distinguished again into radio-loud (RL) BAL QSOs and radio-quiet (RQ) BAL QSOs. The first are very rare, even four times less common than RQ BAL QSOs. The reason for this is still unclear and leaves open questions about the nature of the BAL-producing outflows and their connection with the radio jet.
The parsec-scale structure of radio-loud broad absorption line quasars
Astronomy & Astrophysics, 2013
Context. Broad absorption line quasars (BAL QSOs) belong to a class of objects not well-understood as yet. Their UV spectra show BALs in the blue wings of the UV resonance lines, owing to ionized gas with outflow velocities up to 0.2 c. They can have radio emission that is difficult to characterize and that needs to be studied at various wavelengths and resolutions. Aims. We aim to study the pc-scale properties of their synchrotron emission and, in particular, to determine their core properties. Methods. We performed observations in the Very Long Baseline Interferometry (VLBI) technique, using both the European VLBI Network (EVN) at 5 GHz, and the Very Long Baseline Array (VLBA) at 5 and 8.4 GHz to map the pc-scale structure of the brightest radio-loud objects of our sample, allowing a proper morphological interpretation. Results. A variety of morphologies have been found: 9 BAL QSOs on a total of 11 observed sources have a resolved structure. Core-jet, double, and symmetric objects are present, suggesting different orientations. In some cases the sources can be young GPS or CSS. The projected linear size of the sources, also considering observations from our previous work for the same objects, can vary from tens of pc to hundreds of kpc. In some cases, a diffuse emission can be supposed from the missing flux-density with respect to previous lower resolution observations. Finally, the magnetic field strength does not significantly differ from the values found in the literature for radio sources with similar sizes. Conclusions. These results are not easily interpreted with the youth scenario for BAL QSOs, in which they are generally compact objects still expelling a dust cocoon. The variety of orientations, morphologies, and extensions found are presumably related to different possible angles for the BAL producing outflows, with respect to the jet axis. Moreover, the phenomenon could be present in various phases of the QSO evolution.
Morphology and orientation of radio-loud Broad Absorption Line quasars
Proceedings of 10th European VLBI Network Symposium and EVN Users Meeting: VLBI and the new generation of radio arrays — PoS(10th EVN Symposium), 2011
BAL QSOs are still a not-well understood class of objects. In the UV spectra they show Broad Absorption Lines (BALs) in the blue wings of the UV resonance lines, due to ionized gas with outflow velocities up to 0.2 c. Two different models have been proposed to explain this phe-* Speaker.
Astrophysics and Space Science Proceedings, 2010
Broad Absorption Lines (BALs) seem to be the most extreme manifestations of quasar (QSO) outflows. Two main scenarios have been proposed to explain the nature of BAL QSOs. They may be a physically distinct population (e.g., newborn or recently refuelled QSOs) or present in all QSOs but intercepted by only a fraction of the lines of sight to the QSOs. Our previous observations of a sample of 15 radio BAL QSOs show that they have convex radio spectra typical of Giga-Hertz Peaked-Spectrum (GPS) sources. We have selected a well-defined sample of radio bright BAL QSOs from the Sloan Digital Sky Survey -Data Release 5. Here we present preliminary results on radio continuum observations in full polarisation of this sample, taken with the 100-m Effelsberg radiotelescope at 2.7, 4.8, 8.4 and 10.5 GHz. The aim is to describe the radio spectra and polarisation characteristics of these radio bright BAL QSOs and compare them with our previous results from the study of a radio fainter sample of BAL QSOs and with the properties of normal QSOs where the BAL phenomenon is not seen.
The Broad Line Region of Quasars
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Are radio-loud Broad Absorption Line Quasars young sources?
Astronomische Nachrichten, 2009
For a long time, radio-loud Broad Absorption Line Quasars (BAL QSOs) were thought to be extremely rare objects. The absorbing troughs seen in their optical spectra are due to strong winds which probably have their origin within the inner region of the AGN, as a result of the accretion processes. Their radio emission constitutes an additional diagnostic tool which is successfully contributing new perspectives and raise new questions, with the aim to enrich our understanding of the BAL phenomenon. In this contribution, we introduce a first characterisation of the radio-loud BAL QSO population. Radio continuum spectra have been collected for a sample of 15 objects, which we present together with their radio polarisation properties. VLA maps in A configuration confirm the compactness of these objects at different frequencies up to 43 GHz, yielding projected linear sizes below 1 kpc. We note that many of their radio properties are common to the population of young radio-sources, like Compact Steep Spectrum (CSS) or Gigahertz-Peaked Spectrum (GPS) sources.
Unusual broad absorption line quasars from the Sloan Digital Sky Survey
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The radio-loud fraction of quasars is a strong function of redshift and optical luminosity
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VLBI Detections of Parsec-Scale Nonthermal Jets in Radio-Loud Broad Absorption Line Quasars
Publications of the Astronomical Society of Japan, 2009
We conducted radio detection observations at 8.4 GHz for 22 radio-loud broad absorption line (BAL) quasars, selected from the Sloan Digital Sky Survey Third Data Release, by a very-long-baseline interferometry (VLBI) technique. The VLBI instrument we used was developed by the Optically ConnecTed Array for VLBI Exploration project (OCTAVE), which is operated as a subarray of the Japanese VLBI Network. We aimed to select BAL quasars with nonthermal jets suitable for measuring their orientation angles and ages by subsequent detailed VLBI imaging studies to evaluate two controversial issues of whether BAL quasars are viewed nearly edge-on, and of whether BAL quasars are in a short-lived evolutionary phase of the quasar population. We detected 20 out of 22 sources using the OCTAVE baselines, implying brightness temperatures greater than 10 5 K, which presumably come from nonthermal jets. Hence, BAL outflows and nonthermal jets can be generated simultaneously in these central engines. We also found four inverted-spectrum sources, which are interpreted as Doppler-beamed, pole-on-viewed relativistic jet sources, or young radio sources: single edge-on geometry cannot describe all BAL quasars. We discuss the implications of the OCTAVE observations for investigations for the orientation and evolutionary stage of BAL quasars.