Intrinsic Absorption in Quasars: BALs

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Intrinsic Absorption in QuasarsBALs NALs

• Jonathan Trump
• February 11, 2007

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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 were
  talking about absorption lines by diffuse gas,
  not global obscuration of the BLR by lots of dust!

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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?

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Broad Absorption Line Quasars
from Trump et al. 2006
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Broad Absorption Line Quasars

• Broad absorption
• Typically gt1000 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

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The Zoo of BAL types
from Reichard et al. 2003
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Broad Absorption Line Quasars

• High-Ionization BALs
• CIV 1550 Å, also SiIV, NV, Lya
• 15 of quasars
• Low-Ionization BALs
• MgII 2800 Å, also Al II, Al III
• 1-2 of quasars
• FeLoBALs
• FeII or FeIII (widespread)
• lt0.1 of quasars
• Rarer objects absorption in He, Balmer lines

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FeLoBALs (theyre weird)
from Trump et al. 2006
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FeLoBALs (theyre weird)
from Hall et al. 2007
For more about FeLoBALs, see Hall et al. 2002,
ApJ, 141, 267
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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

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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.

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from Elvis 2000
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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

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BALQSOs in X-rays

• From Brandt et al. 2000
• More UV absorption -gt weaker in soft X-rays

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BALQSOs in X-rays

• weaker X-rays -gt harder spectrum
• Absorbed in soft X-rays only
• Gallagher et al. 2006

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BALQSOs in IR

• If BALQSOs are in a dusty cocoon, wed 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

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BALs from Orientation

• Different absorption mechanisms originate at
  different scales from the central engine

from Gallagher Everett 2007
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Narrow Absorption Lines
from Wise et al. 2004
from Narayanan et al. 2004
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Narrow Absorption Lines

• In gt20 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 lt100 pc from the central source
• gt Intrinsic!
• Really, the only way to determine intrinsic from
  host/intervening but time-consuming

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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

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BALs from Orientation
from Gallagher Everett 2007