Mass Outflow in the Seyfert 1 Galaxy NGC 4151

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Mass Outflows from AGN in Emission and Absorption
Mike Crenshaw (Georgia State University) Steve
Kraemer (Catholic University of America)
NGC 4151
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NGC 4151 UV Light Curve
IUE black pluses HUT red diamonds FOS green
triangles STIS blue xs
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Absorption Components in STIS and FUSE Spectra

• A, C, DE, E? are intrinsic B is Galactic F, F?
  are host galaxy.
• DE (vr -500 km s-1) responsible for bulk of UV
  and X-ray absorption.

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So what are the intrinsic absorbers?

• What is their origin?
• Accretion-disk winds, evaporation from torus?
• What are their dynamics?
• Radiatively-driven, thermal wind, hydromagnetic
  flows? (see Crenshaw,
  Kraemer, George, 2003, ARAA, 41, 117 )
• What observational constraints are needed?
• Physical conditions U (ionization parameter), NH
  (column density), nH (number density),
  abundances, etc.
• Kinematics radial velocity (vr), FWHM,
  transverse velocity (vT)
• Geometry Global covering factor (Cg), LOS
  covering factor (Clos), distribution with respect
  to accretion disk axis (polar angle ?)?
• Radial location (r), mass outflow rate
• Are the absorbers seen in emission?

Yes Emission lines from the high-column absorber
in NGC 4151 provide tight constraints on
dynamical models of the mass outflow.
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Absorption Variability in C IV Region
(Kraemer et al. 2006, ApJ, in press,
astro-ph/0608383)

• DE varies strongly in response to ionizing
  continuum changes.
• DE in 2002 a large amount of gas moved out of
  the LOS.

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Absorption Variability in X-rays
(Kraemer et al. 2005, ApJ, 633, 693)

• X-ray absorption primarily due to DE
• DE decreased in NH between 2000 and 2002
• Evidence for a more highly ionized component
  X-high

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Photoionization Models of High-Column Absorbers

• Density (nH) from metastable C III ? radial
  distance of DE is 0.1 pc
• DEd change in los covering factor ? vT 2100 km
  s-1
• Other constraints?

Yes! DEa is seen in emission.
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Emission-Line Profiles at Low Flux Levels
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Emission-Line Profiles at Low Flux Levels
C IV
blue - narrow red - intermediate green - broad

• DE absorbs ILR and has same velocity extent ?
  self absorption?
• Are we seeing the absorption in emission? ? DEa
  should dominate
• DEa absorber models should match the observed
  ILR line ratios

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Intermediate Components in Other Lines
blue - narrow red - intermediate green - broad
(Crenshaw Kraemer, 2006, ApJ, submitted)
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ILR Line Ratios and DEa Photoionization Models
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Variability of C IV Emission Components

• Both BLR and ILR respond positively to continuum
  changes
• Size of ILR 140 light days (0.12 pc)

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ILR C IV vs. Continuum Flux
Observed --- High-N Model Low-N Model

• High-N model is a better match globally
• Scale factor for High-N model gives Cg 0.4
  (global covering factor)

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Can we constrain the geometry of the ILR?

• Kinematic studies show the NLR of NGC 4151 is
  roughly biconical with a half-opening angle of
  33? and an inclination of 45? (Das et al.
  2005).
• Previous photoionization studies showed the NLR
  is shielded by an absorber with U, NH similar to
  DEa/ILR (Alexander et al. 1999, Kraemer et al.
  2000).
• Thus, the ILR is concentrated in the polar
  direction and extends to ? 45? (? 53 ?
  gives Cg 0.4)

NLR and host galaxy
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Simple Geometric Model

• r 0.1 pc, ? 45?, vr vlos - 490 km s-1
• Assume v? 0, then v? vT 2100 km s-1 (vT
  10,000 km s-1 also shown)
• Emission-line vr 1550 km s-1, close to observed
  HWZI (1400 km s-1)

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Dynamical Considerations

• Consider the high-column absorbers DE and
  X-high
• Radiation pressure
• To be efficient FM gt (Lbol/Ledd)-1 70 for NGC
  4151
• From Cloudy models FM (X-high) lt 2, FM (DEa) lt
  40
• X-high is not radiatively driven and DE is
  marginally susceptible
• Thermal wind
• Radial distance at which gas can escape
• resc 7 pc (X-high), resc 400 pc (DEa)
• Neither are thermally driven.
• Magnetocentrifugal acceleration
• Likely important, at least by comparison to other
  alternatives.
• Gives large transverse velocities and large line
  widths (Bottorff et al. 2000)

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Conclusions

• There is an intermediate-line region (ILR) in NGC
  4151, characterized by FWHM 1170 km s-1.
• The ILR is the same component of outflowing gas
  responsible for the high-column UV and X-ray
  absorption (DEa) at 0.1 pc from the nucleus.
• The ILR has Cg ? 0.4 and it shields the NLR,
  indicating outflow over a large solid angle
  centered on the accretion-disk axis.
• The kinematics at this distance are likely
  dominated by rotation, but there is a significant
  outflow component (vT ? 2100 km s-1 and vr -
  490 km s-1).
• A simple geometric model yields maximum
  emission-line velocities close to the observed
  HWZI of the ILR (1400 km s-1) and significantly
  less than vT.
• The mass outflow rate is 0.16 M? yr-1, about
  10x the accretion rate.
• Dynamical considerations indicate that
  magnetocentrifugal acceleration is favored over
  pure radiation driving or thermal expansion.
• Future work compare these constraints with
  predictions from dynamical models (e.g., Proga
  2003 Chelouche Netzer 2005 Everett 2005).

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THE END