Variation of Ionizing Continuum: The Main Driver of Broad Absorption Line Variability

He, Zhicheng; Wang, Tinggui; Zhou, Hongyan; Bian, Wei-Hao; Liu, Guilin; Yang, Chenwei; Dou, Liming; Sun, Luming

doi:10.3847/1538-4365/aa647a

Cited by 50 publications

(74 citation statements)

References 63 publications

(62 reference statements)

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“…Such a trend is different from what is typically observed in luminous quasars, for which the weakening of BAL trough is often accompanied with the brightening of continuum (e.g., Wang et al 2015;He et al 2017;Pinto et al 2018). This may be explained by the different ionization states between WPVS 007 and quasars.…”

Section: Change Of Ionization State and Bal Trough Strengthcontrasting

confidence: 88%

“…Instead, the coordinated correlation can be easily explained if the BAL variability is photoionization-driven (e.g., Hamann et al 2011;FilizAk et al 2012FilizAk et al , 2013Wang et al 2015;He et al 2017). As pointed out in Section 4.1, the C iv and Si iv column densities decrease when the source becomes fainter.…”

Section: Coordination Between Outflow Velocity and Agn Luminositymentioning

confidence: 99%

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On the origin of the dramatic spectral variability of WPVS 007

Wang

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We report the discovery of large-amplitude mid-infrared variabilities (MIR; ∼ 0.3 mag) in the Wide-field Infrared Survey Explorer W1 and W2 bands of the low-luminosity narrow-line Seyfert 1 galaxy WPVS 007, which exhibits prominent and varying broadabsorption lines (BALs) with blueshifted velocity up to ∼ 14000 km s −1 . The observed significant MIR variability, the UV to optical color variabilities in the Swift bands that deviate from the predictions of pure dust attenuation models, and the fact that Swift light curves can be well fitted by the stochastic AGN variability model suggest that its observed flux variabilities in UV-optical-MIR bands should be intrinsic, rather than owing to variable dust extinction. Furthermore, the variations of BAL features (i.e., trough strength and maximum velocity) and continuum luminosity are concordant. Therefore, we propose that the BAL variability observed in WPVS 007 is likely induced by the intrinsic ionizing continuum variation, alternative to the rotating-torus model proposed in a previous work. The BAL gas in WPVS 007 might be in the lowionization state as traced by its weak N v BAL feature; as the ionizing continuum strengthens, the C iv and Si iv column densities also increase, resulting in stronger BALs and the emergence of high-velocity components of the outflow. The outflow launch radius might be as small as ∼ 8 × 10 −4 pc under the assumption of being radiatively driven, but a large-scale origin (e.g., torus) cannot be fully excluded because of the unknown effects from additional factors, e.g., the magnetic field.

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Section: Change Of Ionization State and Bal Trough Strengthcontrasting

confidence: 88%

Section: Coordination Between Outflow Velocity and Agn Luminositymentioning

confidence: 99%

On the origin of the dramatic spectral variability of WPVS 007

Wang

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…Our initial sample consists of 2005 BAL quasars constructed by He et al (2017) from the SDSS-I/II/III. Among them, there are 46 quasars have at least fiveepoch observations and a signal-to-noise ratio (S/N) level of S/N>10 in one-epoch observation at least.…”

Section: Sample Selection and Correlation Analysismentioning

confidence: 99%

“…When the absorbing gas are at a relatively low ionization state, the EW of the C IV/Si IV BAL show positive response to the continuum variation, otherwise, the negative response reveals the relatively high ionization state. On the other hand, based on large absorption line samples, statistical studies in both BALs (e.g., Wang et al 2015;He et al 2017) and NALs (Lu et al 2017;Chen et al 2018b) also showed that the variations of intrinsic absorption lines are positively or negatively responded to the alternations of quasar continua. These two kinds of respond suggest that the variable intrinsic absorption lines can be divided into at least two classes: one is highly ionized systems dominated by absorbing gas in high ionization and show negative response to changes of quasar emissions; and the other is lowly ionized systems dominated by absorbing gas in low ionization and show positive response to changes of quasar emissions.…”

Section: Positive Vs Negative Correlationsmentioning

confidence: 99%

“…Based on a sample of 452 quasars from the Sloan Digital Sky Survey Data Release 10 (SDSS DR10), Wang et al (2015) qualitatively confirmed that the variations of C IV, N V, and Si IV BALs/mini-BALs show high synchronization with those of the ionizing continuum and emission lines, and concluded that the variability of the absorption lines is driven mainly by variations in the gas ionization as response to the continuum variations. Based on the statistical analysis of a sample of 2005 BAL quasars from the SDSS-I/II/III, He et al (2017) further concluded that variability of BAL in more than 80% of quasars are caused by the variation of the ionizing continuum. More recently, correlation between the variation of the ionizing continuum and BALs has been confirmed by several papers Vivek 2019).…”

Section: Introductionmentioning

confidence: 99%

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Correlations between the Variation of the Ionizing Continuum and Broad Absorption Lines in Individual Quasars

Lin

2019

ApJ

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We discover the significant (significance level of >99%) correlations between the fractional variation of the ionizing continuum and that of the C IV and/or Si IV BALs in each of 21 BAL quasars that have at least five-epoch observations from the Sloan Digital Sky Survey-I/II/III. This result reveals that the fluctuation of the ionizing continuum is the driver of most of these BAL variations. Among them, 17 show negative correlations and the other 4 positive correlations, which agrees with the prediction of photoionization models that absorption line variability response to ionization changes is not monotonic. 8 quasars out of 21 examples have been observed at least 30 times on rest-frame timescales as short as a few days, which reveals that changes in the incident ionizing continuum can cause BAL variability even in such a short period of time. In addition, we find that most of the 21 quasars show larger variation amplitude in Si IV than C IV, which reveals the ubiquity of saturation in these BALs (at least for C IV BALs).

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The properties of broad absorption line outflows based on a large sample of quasars

Wang

Liu

et al. 2019

Nat Astron

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Quasar outflows carry mass, momentum and energy into the surrounding environment, and have long been considered a potential key factor in regulating the growth of supermassive black holes and the evolution of their host galaxies [1][2][3][4] . A crucial parameter for understanding the origin of these outflows and measuring their influence on their host galaxies is the distance (R) between the outflow gas and the galaxy center 5, 6 . While R has been measured in a number of individual galaxies 7-15 , its distribution remains unknown. Here we report the distributions of R and the kinetic luminosities of quasars outflows, using the statistical properties of broad absorption line variability in a sample of 915 quasars from the Sloan Digital Sky Surveys. The mean and standard deviation of the distribution of R are 10 1.4±0.5 parsecs. The typical outflow distance in this sample is tens of parsec, which is beyond the theoretically predicted location (0.01 ∼ 0.1 parsecs) where the accretion disc line-driven wind is launched 16,17 , but is smaller than the scales of most outflows that are derived using the excited state absorption lines 7-14 . The typical value of the mass-flow rate is of tens to a hundred solar masses per year, or several times the accretion rate. The typical kinetic-to-bolometric luminosity ratio is a few per cent, indicating that outflows are energetic enough to influence the evolution of their host galaxies.Nowadays, theoretical models for galaxy formation and evolution routinely invoke the concept of "quasar feedback"-the strong effect that the active supermassive black hole's (SMBH) energy output exerts on its host galaxy-to keep massive galaxies from forming many stars and becoming overly massive. In 10-40% of the quasars in which the central source and outflowing gas are both in the line of sight, outflows may manifest themselves as broad absorption lines (BALs) 18,19 and BAL outflows are therefore a candidate agent of quasar feedback. The importance of outflows to active galactic nucleus (AGN) feedback can be quantified using the mass-flow rate (Ṁout) and the kinetic luminosity (Ė k ) of the outflowing material. TheṀout and theĖ k of a BAL outflow can be estimated from the distance (R) between the out- * flowing gas and the galaxy center, the total hydrogen column density NH and the fraction Ω of the solid angle subtended by the outflowing gas. Because the ionization parameter UH of the plasma is inversely proportional to the product of hydrogen number density nH and R 2 , i.e., UH ∝ 1/(nHR 2 ), R can be obtained by measuring UH and nH. In general, nH can be determined from the absorption lines of the excited states of ions (e.g., Fe II*, Si II*, S IV*), but this method is hindered by line blending and is therefore only applicable to quasars with relatively narrow absorption lines. During the last decade or so, outflow distances have been measured for only about a dozen of individual quasars using this method 7-14 , while the distributions of primary properties of BAL outflows remain in unknown. ...

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Variation of Ionizing Continuum: The Main Driver of Broad Absorption Line Variability

Cited by 50 publications

References 63 publications

On the origin of the dramatic spectral variability of WPVS 007

On the origin of the dramatic spectral variability of WPVS 007

Correlations between the Variation of the Ionizing Continuum and Broad Absorption Lines in Individual Quasars

The properties of broad absorption line outflows based on a large sample of quasars

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