Polar Outflows in Six Broad Absorption Line Quasars

Zhou, Hongyan; Wang, Tinggui; Wang, Huiyuan; Wang, Junxian; Yuan, Weimin; Lu, Yu

doi:10.1086/499768

Cited by 104 publications

(141 citation statements)

References 40 publications

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“…We however note that at higher frequency variability may be more important. We do not identify any of the sources from Ghosh & Punsly (2007) or Zhou et al (2006) as significantly variable, though there is overlap between our samples, due both to the use here of integrated fluxes from both surveys as well as the more strict cut of σ var > 4.…”

Section: Variability and Polar Bals?mentioning

confidence: 85%

A Very Large Array Survey of Radio-Selected SDSS Broad Absorption Line Quasars

DiPompeo

Brotherton

Breuck

et al. 2011

ApJ

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We have built a sample of 74 radio-selected broad absorption line quasars from the Sloan Digital Sky Survey Data Release 5 (SDSS DR5) and Faint Images of the Radio Sky at Twenty Centimeters (FIRST), along with a well matched sample of 74 unabsorbed "normal" quasars. The sources have been observed with the NRAO Very Large Array/Expanded Very Large Array at 8.4 GHz (3.5 cm) and 4.9 GHz (6 cm). All sources have additional archival 1.4 GHz (21 cm) data. Here we present the measured radio fluxes, spectral indices, and our initial findings. The percentage of BAL quasars with extended structure (on the order of 10%) in our sample is similar to previous studies at similar resolutions, suggesting that BAL quasars are indeed generally compact, at least at arsecond resolutions. The majority of sources do not appear to be significantly variable at 1.4 GHz, but we find two previously unidentified BAL quasars that may fit into the "polar" BAL category. We also identify a significant favoring of steeper radio spectral index for BAL compared to non-BAL quasars. This difference is apparent for several different measures of the spectral index, and persists even when restricting the samples to only include compact objects. Because radio spectral index is a statistical indicator of viewing angle for large samples, these results suggest that BAL quasars do have a range of orientations but are more often observed farther from the jet axis compared to normal quasars.

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Section: Variability and Polar Bals?mentioning

confidence: 85%

A Very Large Array Survey of Radio-Selected SDSS Broad Absorption Line Quasars

DiPompeo

Brotherton

Breuck

et al. 2011

ApJ

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“…The magnitude of this effect is not clear and is affected by the fact that we do not yet have a full theoretical exploration of the accretion disk/wind paradigm. (For example, the orientation of radio jets and polarization of light in the troughs in some radio-loud BALs seem to indicate a range of accretion disk orientations [Zhou et al 2006;Brotherton et al 2006], but the opening angle of the wind may also be important.) Moreover, while the existence of the v max YkL k (3000 8) envelope indicates the importance of radiation pressure in driving the BAL outflow, this is not the only possible mechanism.…”

Section: Radiatively Driven Winds?mentioning

confidence: 99%

Outflows and the Physical Properties of Quasars

Ganguly

Brotherton

Cales

et al. 2007

ApJ

128

147

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We have investigated a sample of 5088 quasars from the SDSS DR2 in order to determine how the frequency and properties of BALs depend on black hole mass, bolometric luminosity, Eddington fraction (L/L Edd ), and spectral slope. We focus only on high-ionization BALs and find a number of significant results. While quasars accreting near the Eddington limit are more likely to show BALs than lower L/L Edd systems, BALs are present in quasars accreting at only a few percent Eddington. We find a stronger effect with bolometric luminosity, such that the most luminous quasars are more likely to show BALs. There is an additional effect, previously known, that BAL quasars are redder on average than unabsorbed quasars. The strongest effects involving the quasar physical properties and BAL properties are related to terminal outflow velocity. Maximum observed outflow velocities increase with both the bolometric luminosity and the blueness of the spectral slope, suggesting that the ultraviolet luminosity to a great extent determines the acceleration. These results support the idea of outflow acceleration via ultraviolet line scattering.

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“…In this case the percentage of BAL QSOs would constrain the solid angle of the outflow. The bipolar wind model proposed by Punsly (1999a,b) was used by Ghosh & Punsly (2007) to explain the polar BAL QSOs found by Zhou et al (2006): in this model the BAL outflow would be aligned with the polar axis, while the relativistic jet would be nested inside of it. Recent works, based on large samples, do not confirm a young age for all BAL QSOs, but also a variety of orientations have been found (Bruni et al 2012;DiPompeo et al 2011).…”

Section: Introductionmentioning

confidence: 99%

The parsec-scale structure of radio-loud broad absorption line quasars

Bruni

Dallacasa

Mack

et al. 2013

A&A

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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.

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Polar Outflows in Six Broad Absorption Line Quasars

Cited by 104 publications

References 40 publications

A Very Large Array Survey of Radio-Selected SDSS Broad Absorption Line Quasars

A Very Large Array Survey of Radio-Selected SDSS Broad Absorption Line Quasars

Outflows and the Physical Properties of Quasars

The parsec-scale structure of radio-loud broad absorption line quasars

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