Intrinsic Absorption in Quasars:

BALs & NALs

Jonathan TrumpFebruary 11, 2007

Quasar Absorption Lines

• Intrinsic– Caused by material in the AGN engine itself

• Host– From gas in the host galaxy

• Intervening– From an intervening galaxy

This all has nothing to do with Type 2 AGN: we’re talking about absorption lines by diffuse gas, not global obscuration of the BLR by lots of dust!

Why Should We Care?

• Dynamics– Mechanism for losing angular momentum?– Accretion disk as power source for winds– Effects on host?

• Composition– Densities– Abundances

• Unified Model– Evolution? Orientation?

Broad Absorption Line Quasars

from Trump et al. 2006

• Broad absorption– Typically >1000 km/s– Up to ~20,000 km/s

• Blueshifted from emission line– Typically few thousand km/s (~0.01c)– Up to ~60,000 km/s (0.2c)

• Outflowing gas “wind”– High velocity dispersion– High velocity

Broad Absorption Line Quasars

The Zoo of BAL types

from Reichard et al. 2003

• High-Ionization BALs– CIV 1550 Å, also SiIV, NV, Lyα– ~15% of quasars

• Low-Ionization BALs– MgII 2800 Å, also Al II, Al III– ~1-2% of quasars

• FeLoBALs– FeII or FeIII (widespread)– <0.1% of quasars

• Rarer objects: absorption in He, Balmer lines…

Broad Absorption Line Quasars

FeLoBALs (they’re weird)

from Trump et al. 2006

FeLoBALs (they’re weird)

For more about FeLoBALs, see Hall et al. 2002, ApJ, 141, 267

from Hall et al. 2007

Characterizing BALs

• Balnicity Index (BI)– Weymann et al. 1991– Limits width, min/max blueshift, depth

• Absorption Index (AI)– Hall et al. 2002– Less limiting than BI, includes mini-BALs

• Characterization limited by S/N of spectra• BALQSOs are red, and LoBALs are redder• BALQSO fraction

– Underestimated by all surveys: fainter, redder, obscured in X-rays

• Typically saturated, but with partial coverage

km/s 25000

km/s 3000 901 Cdv.vf

km/s 25000

km/s 0'1 dvCvf

What Causes BALs?

• Evolution– Young quasars in a dusty cocoon– Especially considered for LoBALs

• Orientation– Disk-driven wind in all quasars– Only visible in BALs because of orientation– Supporting evidence: Increased trough

velocity with luminosity (Trump et al. 2006)– See models by Murray & Chiang 1998, Proga

et al. 2000, etc.

from Elvis 2000

BALQSOs in Radio

• LBQS (Weymann et al. 1991): surprising lack of radio-loud BALQSOs

• SDSS (Reichard et al. 2003): same findings…– 10% of quasars are radio-loud, but only a few

percent of BALQSOs are radio-loud

• Supports orientation

BALQSOs in X-rays

• From Brandt et al. 2000

• More UV absorption -> weaker in soft X-rays

BALQSOs in X-rays

weaker X-rays -> harder spectrum

Absorbed in soft X-rays only

Gallagher et al. 2006

BALQSOs in IR

• If BALQSOs are in a dusty cocoon, we’d expect stronger IR emission– Not the case!

• Spitzer survey of Gallagher et al. 2007 find similar properties to normal QSOs

• Occasionally, some narrow absorption in IR

BALs from Orientation

Different absorption mechanisms originate at different scales from the central engine

from Gallagher & Everett 2007

Narrow Absorption Lines

from Narayanan et al. 2004

from Wise et al. 2004

Narrow Absorption Lines

• In >20% of all quasars (Wise et al. 2004), but hard to ID because of S/N & host/intervening lines

• Variability– Variable on the order of ~1 yr– Implies scales of <100 pc from the central

source– > Intrinsic!– Really, the only way to determine intrinsic

from host/intervening… but time-consuming

BALs & NALs: In Summary

• BALs: big, broad, blueshifted absorption– High velocities & velocity dispersions require AGN

engine

• NALs: narrow, blueshifted absorption– High velocities & variability require AGN engine

• Typically weaker in X-rays, radio• Mid-IR “normal”• Probably caused by orientation

– Disk-driven winds– But LoBALs are tougher to explain…

BALs from Orientation

from Gallagher & Everett 2007