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Journal article
A disc wind model for blueshifts in quasar broad emission lines
Monthly notices of the Royal Astronomical Society, v 526(3)
Dec 2023
Abstract
Abstract Blueshifts - or, more accurately, blue asymmetries - in broad emission lines such as C iv λ1550 are common in luminous quasars and correlate with fundamental properties such as Eddington ratio and broad absorption line (BAL) characteristics. However, the formation of these blueshifts is still not understood, and neither is their physical connection to the BAL phenomenon or accretion disc. In this work, we present Monte Carlo radiative transfer and photoionization simulations using parametrized biconical disc-wind models. We take advantage of the azimuthal symmetry of a quasar and show that we can reproduce C iv blueshifts provided that (i) the disc-midplane is optically thick out to radii beyond the line formation region, so that the receding wind bicone is obscured; and (ii) the system is viewed from relatively low (that is, more face-on) inclinations (≲ 40○). We show that C iv emission line blueshifts and BALs can form in the same wind structure. The velocity profile of the wind has a significant impact on the location of the line formation region and the resulting line profile, suggesting that the shape of the emission lines can be used as a probe of wind-driving physics. While we are successful at producing blueshifts/blue asymmetries in outflows, we struggle to match the detailed shape or skew of the observed emission line profiles. In addition, our models produce redshifted emission-line asymmetries for certain viewing angles. We discuss our work in the context of the C iv λ1550 emission blueshift versus equivalent-width space and explore the implications for quasar disc wind physics.
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8 citations in Scopus
Details
- Title
- A disc wind model for blueshifts in quasar broad emission lines
- Creators
- James H Matthews (Corresponding Author) - University of OxfordJago Strong-Wright - University of CambridgeChristian Knigge - University of SouthamptonPaul Hewett - University of CambridgeMatthew J Temple - Universidad Diego PortalesKnox S Long - Space Telescope Science InstituteAmy L Rankine - Royal ObservatoryMatthew Stepney - University of SouthamptonManda Banerji - University of SouthamptonGordon T Richards - Drexel University
- Publication Details
- Monthly notices of the Royal Astronomical Society, v 526(3)
- Publisher
- Oxford University Press
- Resource Type
- Journal article
- Language
- English
- Academic Unit
- Physics
- Scopus ID
- 2-s2.0-85175624337
- Other Identifier
- 991021436031904721