Transcript Mass Outflow in the Seyfert 1 Galaxy NGC 4151

Micro-Turbulence in Emission and Absorption in
AGN
Steve Kraemer (Catholic Univ. of America)
Via collaborations with:
Mike Crenshaw (GSU), Mark Bottorff (Southwestern), Jane
Turner (UMBC), Lance Miller (Oxford)
Is Micro-Turbulence Present?
•
Emission lines in AGN are broad. In Seyferts
galaxies, FWHM for optical UV Broad Lines <
10,000 km/sec; NLR lines < 1000 km/sec
• In general, widths decrease with distance from
the central source
• In all cases, FWHM >> thermal (~ few km/sec).
Possibilities:
1. Superposition of knots with range in velocities.
2. Micro-Turbulence
• Superposition likely. Central knots seen in [OIII] with very
large dispersions.
• BLR emission lines are very smooth (e.g. Dietrich et al.
1999). If thermal, need huge number within light-days of
central potential
• Bottorff &Ferland (2000) – BLR clouds internally
turbulent. vturb >> vthermal
• Note: turbulence present in ISM. Larson (1981) – powerlaw correlation btw molecular cloud sizes and line widths
(see Elmegreen & Scalo 2004) –
Why not in AGN?
• Causes of turbulence in ISM:
1. Stars – via winds and Supernovae
2. Galactic rotation
3. Gaseous self-gravity/cloud collapse
4. Kelvin-Helmholtz and other fluid instabilities
v
Fluid Mechanics:
convective acceleration: time independent
acceleration of fluid w.r.t space
non-linear advection operator → distortion of
velocity field
• Bottorff & Ferland (2002) – included dissipative heating w/micro –
turbulence for BLR. With heating rate Q:
Q = ην ρ (vturb 3 /D) ergs cm-3 s-1
(v
turb equivalent to b or 1/1.665 FWHM)
• We applied same formalism for NLR emission-line gas:
NV 1240,
affected by
photoexcitation +
heating,
[NeV] 3426
bossted by
heating.
High resolution X-ray spectra of AGN show myriad of soft
X-ray emission lines arising in NLR
Ratios of resonance to forbidden lines in He-like triplets can
indicate temperature and density. High r/f ratios: collisionally
excited gas (Ogle et al. 2000); Photo-excitation (Sako et al.
2000; Kinkhabwala et al. 2002)/
Narrowness of Radiative Recombination Continua suggests low
Temps (Photo-ionization) → photo-excitation.
But photo-excitation depends strongly on vturb
Sim of OVII triplet, courtesy
of R. Porter.
Cloudy models, (logU=0),
showing dependence of r/f ratio
on vturb and column density.
Is turbulence
present in
intrinsic
absorbers?
Most readily
answered using
high-res UV
spectra of Type 1
Seyferts.
STIS spectra of NGC 5548, showing multiple
kinematic components in HI, NV, and CIV. Note
the difference in the profiles.
STIS spectra of NGC
3783 (Gabel et al.
2003), showing
variations in
absorption over three
epochs, separated by
13 and 9 months.
Radial velocity
changes or profile
changes (superposition
of components)?
Comparison of FWHM
and total H column
densities (derived from
photo-ionization models)
for absorbers in NGC
3516, NGC 4051, NGC
4151, NGC 5548, and
Mrk 509 (Crenshaw, in
prep). Note even smallest
large column density
absorbers have superthermal widths.
Slope of Nh to FWHM is ~ 1.5. For Kolmogorov cascade, slope is unity.
Note: slope is flatter for the lower envelope. Combination of turbulence
and superposition?
If minimum widths due to turbulence, what would we see?
Two cases, logU=-1.5, logNh=20.5
FWHM = 1000 km/s at face;
exponential decay. Local value of
vturb has strong effect.
FWHM = 1000 km/s at face; no
decay. Profile difference
dominated by differences in ionic
columns and oscillator strengths.
Conclusions? Perhaps “open questions” is better term:
1. Are emission lines enhanced by turbulence?
2. Are smooth line profiles due to turbulence?
3. How is the turbulence generated?
4. Does turbulence damp out? If so , how and over what
scale lengths (see Mark Bottorff)
5. Is there associated dissipative heating?
6. How does this affect cloud lifetimes, acceleration, etc.