Files and links (1)
Preprint (Author's original)arXiv.org - Non-exclusive license to distribute, Open
Preprint
A disc wind model for blueshifts in quasar broad emission lines
25 Sep 2023
Abstract
Blueshifts - or, more accurately, blue asymmetries - in broad emission lines
such as CIV $\lambda$1550 are common in luminous quasars and correlate with
fundamental properties such as Eddington ratio and broad absorption line (BAL)
characteristics. However, the formation of these blueshifts is still not
understood, and neither is their physical connection to the BAL phenomenon or
accretion disc. In this work, we present Monte Carlo radiative transfer and
photoionization simulations using parametrized biconical disc-wind models. We
take advantage of the azimuthal symmetry of a quasar and show that we can
reproduce CIV blueshifts provided that (i) the disc-midplane is optically thick
out to radii beyond the line formation region, so that the receding wind bicone
is obscured; and (ii) the system is viewed from relatively low (that is, more
face-on) inclinations ($\lesssim40^\circ$). We show that CIV 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 CIV $\lambda$1550
emission blueshift versus equivalent-width space and explore the implications
for quasar disc wind physics.
Metrics
10 Record Views
Details
- Title
- A disc wind model for blueshifts in quasar broad emission lines
- Creators
- James H MatthewsJago Strong-WrightChristian KniggePaul HewettMatthew J TempleKnox S LongAmy L RankineMatthew StepneyManda BanerjiGordon T Richards
- Resource Type
- Preprint
- Language
- English
- Academic Unit
- Physics
- Other Identifier
- 991021229415504721