CIV Emission as a Probe of Accretion Disk Winds

Gordon RichardsDrexel University

With thanks to Sarah Gallagher (UWO), Karen Leighly (OU), Paul Hewett (IoA, Cambridge), and Nick Kruczek, Rachael Kratzer, and Coleman Krawczyk (Drexel)

Urry & Padovani 1995

Clouds (and Torus?) => Disk Winds

Elvis 2000

Proga 2005 (see also Everett 2005)

BELR = Disk+Wind?

2-component BELR as in Collin et al. 2006, shielding gas as in Murray et al. 2000, Gallagher et al. 2006

BELRBELR

We consider a model where the Broad Emission Line Region comes from both the disk and the wind (e.g., Leighly 2004, Collin et al. 2006).If the wind is stronger, the disk component is more shielded from ionizing photons (and thus is weaker) and vice versa.

Filtered ContinuumIn the model of Leighly 2004, the disk isn’t just a separate component, it sees a different continuum than the wind (and possibly different from what we see [e.g. Korista 1997]).

Leighly 2004; Leighly & Casebeer 2007

Disk+Wind

Leighly 2004

A Range of Intrinsic SEDs

Leighly et al. 2007

While the disk may see a different filtered continuum for different strength winds, the structure of the wind depends on the intrinsic SED. BALs

Not BALs

Winds from EmissionWe use 2 key emission line diagnostics from CIV in the redshift range where BALs are found to learn more about winds.

Specifically, we can place objects along a continuum of BELR properties ranging from “disk”- to “wind”-dominated.

This helps to identify the parent sample of objects from which BALQSOs are drawn.

These parameters may also describe unbiased tracers of mass and accretion rate.

The Baldwin Effect

Richards et al. 2011

More luminous quasars have weaker CIV lines (Baldwin 1977).

Seen here from an SDSS sample with 30k quasars.

Dietrich et al. 2002 explores many other lines.

CIV “Blueshifts”

The peak of CIV emission is generally not at the expected laboratory wavelength (e.g., Gaskel 1982).

Richards et al. 2011, with redshifts from Hewett & Wild 2010

CIV Parameter Space

Radio-Loud

BALQSOs

Richards et al. 2011

Can form a joint parameter space with these two observations.

Generally speaking radio-loud quasars and BALQSOs live in opposite corners.

EV1

Sulentic et al. 2000

At low-z EV1 parameters show a similar distribution.Sulentic calls these Pop A/B, but it may be possible to use a more physically motivated terminology.

SED Extrema

Kruczek et al. 2011

These objects have (hard) SEDs like this.

These objects have (soft) SEDs like this.

CIV Parameter Space

Radio-Loud

BALQSOs

Richards et al. 2011

Ionizing SED, Weak LD winds

Less ionizing SED, Strong LD winds

SEDs affect winds, which affect BAL covering fractions. 40%

0%

More ionizing flux = strong disk componentHigh radio-loud prob; low BALQSO prob

Less ionizing flux = strong wind componentLow radio-loud prob; high BALQSO prob

SEDs vs. M, Mdot

Boroson 2002

K. Leighly

Bolometric Correction BiasesAccretion rates (and Eddington Ratios) are estimated from the Bolometric Luminosity.

The Bolometric Luminosity, in turn, is estimated from a Monochromatic Luminosity and a universal bolometric correction based on a universal SED.

But these have different SEDs and thus (systematically) different bolometric corrections.

Bolometric Correction Biases IIThe situation may be even worse than you think as this plot from before simply extrapolated between the UV and X-ray.

However, there has long been evidence that the (unseen) EUV part of the SED might look different (e.g., Korista et al. 1997) In fact, I’d argue that the

“hard”-spectrum SEDs may look something more like this.

Mass Biases I

All reverberation-mapped AGNs live here.Scaling relations derived from these objects may not apply here.

CIV vs. Others

• Obviously CIV, but what about MgII or Hbeta?• Wang et al. 2011: MgII is consistent

with being from the disk and CIV from both.• Steinhardt and Silverman 2011 results

further support this and may argue for Hbeta also being from both.

Mass Biases II

BELRBELR

The wind may influence even disk measurements if it biases the R-L relationship.Same Ls may have different Rs if the continuum reaching the disk is filtered differently.

M-L: The Bottom LineMean mass and accretion rates may be fine, but it could be dangerous to make comparisons between extrema.

Eddington Ratio can be a dangerous parameter as high M, high Mdot != low M, low Mdot.

RL

BAL

M

€

˙ M

Time/Spin?

Conclusions• Strong evidence for a 2-component BELR (a

disk and a wind).• CIV (and other) emission provides a way for

determining the relative strengths of these components.• “Hard” SEDs have weak winds and “Soft”

SEDs have strong winds.• It is important to explore potential biases in

estimates of mass and accretion rate across this parameter space.