X-Ray Insights Into the Physics of Mini-Bal Quasar Outflows

Gibson, R. R.; Brandt, W. N.; Gallagher, S. C.; Schneider, Donald P.

doi:10.1088/0004-637x/696/1/924

Cited by 58 publications

(74 citation statements)

References 43 publications

(86 reference statements)

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“…The Chandra observations reveal weak or negligible amounts of X-ray absorption, with ∆α ox = α ox (observed) − α ox (expected) typically 0.0 to −0.1 and spectral fitting to the brightest individual source (also [13]) and joint fitting to the ensemble dataset indicating total X-ray column densities N H < 2 × 10 22 cm −2 of neutral-equivalent absorption. These results are consistent with previous studies of lower-velocity mini-BALs that find X-ray absorbing columns at least an order of magnitude less than typical BAL quasars [8,14]. optical depths apply to the short wavelength components of the doublets C IV λ 1548, N V λ 1239, O VI λ 1032, and Ne VIII λ 770.…”

Section: Radiative Shielding In High-velocity Mini-bal Outflowssupporting

confidence: 92%

The physics and physical properties of quasar outflows

Hamann¹

2013

Proceedings of Nuclei of Seyfert Galaxies and QSOs - Central Engine &Amp; Conditions of Star Formation — PoS(Seyfert 2012)

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We describe two studies designed to characterize the total column densities, kinetic energies, and acceleration physics of broad absorption line (BAL) outflows in quasars. The first study uses new Chandra X-ray and ground-based rest-frame UV observations of 7 quasars with mini-BALs at extreme high speeds, in the range 0.1c to 0.2c, to test the idea that strong radiative shielding (and therefore strong X-ray absorption) is needed to moderate the mini-BAL ionizations and facilitate their acceleration to extreme speeds. We find that the X-ray absorption is weak or absent, with generally N H < few × 10 22 cm −2 , and that radiative shielding is not important. We argue that the mini-BAL ionizations are controlled, instead, by high gas densities of order n H ∼ 4 × 10 8 cm −3 in small outflow substructures. If we conservatively assume that the total column density in the mini-BAL gas is N H < 10 22 cm −2 , covering >15% of the UV continuum source along our lines of sight (based on measured line depths), then the radial thickness of these outflows is only ∆R < 3 × 10 13 cm and their transverse size is >8 × 10 15 cm. Thus the outflow regions have the shape of very thin "pancakes" viewed face-on, or they occupy larger volumes like a spray of dense cloudlets with a very small volume filling factor. We speculate that this situation (with ineffective shielding and small dense outflow substructures) applies to most quasar outflows, including BALs. Our second study focuses from BALs of low-abundance ions, mainly PV 1118,1128 Å, whose significant strengths imply large column densities, N H > 10 22 cm −2 , that can further challenge models of the outflow acceleration. In spite of the difficulties of finding this line in the Lyα forest, a search through the SDSS DR9 quasar catalog reveals >50 BAL sources at redshifts z > 2.3 with strong PV BALs, which we are now using to characterize the general properties of high-column outflows.

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Section: Radiative Shielding In High-velocity Mini-bal Outflowssupporting

confidence: 92%

The physics and physical properties of quasar outflows

Hamann¹

2013

Proceedings of Nuclei of Seyfert Galaxies and QSOs - Central Engine &Amp; Conditions of Star Formation — PoS(Seyfert 2012)

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“…A similar trend with X-ray emission is found for broad absorption line (BAL) quasars, which are believed to represent the ≈ 20-40% of quasars (with evidence for a redshift dependence; e.g., Allen et al 2011) for which the nuclear continuum is viewed through the outflow (there is evidence that maybe all quasars host energetic winds; Ganguly & Brotherton 2008). The maximum blueshift in BAL quasars (corresponding to the terminal velocity of the wind) is higher for sources with weaker Xray emission (e.g., Gallagher et al, 2006;Gibson et al, 2009). Both these and the results on C iv blueshifts can be understood in terms of radiation driving of the quasar wind; with a weaker X-ray continuum (possibly associated with an absorber near the midplane), the gas close to the BH is less highly ionized and so more easily driven by the UV continuum radiation from the quasars.…”

Section: Radiatively-driven Windsmentioning

confidence: 99%

What drives the growth of black holes?

Alexander

Hickox

2012

New Astronomy Reviews

595

501

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Massive black holes (BHs) are at once exotic and yet ubiquitous, residing in the centers of massive galaxies in the local Universe. Recent years have seen remarkable advances in our understanding of how these BHs form and grow over cosmic time, during which they are revealed as active galactic nuclei (AGN). However, despite decades of research, we still lack a coherent picture of the physical drivers of BH growth, the connection between the growth of BHs and their host galaxies, the role of large-scale environment on the fueling of BHs, and the impact of BH-driven outflows on the growth of galaxies. In this paper we review our progress in addressing these key issues, motivated by the science presented at the "What Drives the Growth of Black Holes?" workshop held at Durham on 26 th -29 th July 2010, and discuss how these questions may be tackled with current and future facilities.

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“…Broad absorption lines (BALs) up to velocity in 0.2 c from the correspondent emission lines are seen in about 10-40% of quasar population (e.g. Gibson et al 2009;Allen et al 2011). Technically, they are defined as absorption troughs with velocity widths >2000 km s −1 at depths >10 per cent below the contin-uum (Weymann et al 1991).…”

Section: Introductionmentioning

confidence: 99%

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

Wang

Zhou

et al. 2017

ApJS

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We present a statistical analysis of the variability of broad absorption lines (BALs) in quasars using the large multi-epoch spectroscopic dataset of the Sloan Digital Sky Survey Data Release 12 (SDSS DR12). We divide the sample into two groups according to the pattern of the variation of C iv BAL with respect to that of continuum: the equivalent widths (EW) of the BAL decreases (increases) when the continuum brightens (dims) as group T1; and the variation of EW and continuum in the opposite relation as group T2. We find that T2 has significantly (P T < 10 −6 , Students T Test) higher EW ratios (R) of Si iv to C iv BAL than T1. Our result agrees with the prediction of photoionization models that C +3 column density increases (decreases) if there is a (or no) C +3 ionization front while R decreases with the incident continuum. We show that BAL variabilities in at least 80% quasars are driven by the variation of ionizing continuum while other models that predict uncorrelated BAL and continuum variability contribute less than 20%. Considering large uncertainty in the continuum flux calibration, the latter fraction may be much smaller. When the sample is binned into different time interval between the two observations, we find significant difference in the distribution of R between T1 and T2 in all time-bins down to a ∆T < 6 days, suggesting that BAL outflow in a fraction of quasars has a recombination time scale of only a few days.

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X-Ray Insights Into the Physics of Mini-Bal Quasar Outflows

Cited by 58 publications

References 43 publications

The physics and physical properties of quasar outflows

The physics and physical properties of quasar outflows

What drives the growth of black holes?

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

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