Transcript Observational issues - Central engines in AGN

Essay:
What I learned during my
Xi’an “Vacation”
Joe Shields
Ohio University
To make sense of it all we just need to understand…
DUST
Reasons to pay attention to dust
1. Dust central to understanding the torus
- it’s small, but resolved (Jaffe, Davies)
- it’s clumpy (Elitzur, Hoenig poster, …)
- it defines the boundary of the BLR (Laor, Suganuma)
Reverberation Radius of Inner Dust Torus
Suganuma et al.
The Central Engine of Active Galactic Nuclei
Xi’an, Oct. 16-21, 2006
Lag time vs. Optical Luminosity with
BLR lags
NIR(K-band)
F9:
Broad
Emission
Line
Clavel et al. (+89)
Rodriguez-Pascual et al. (+97)
Peterson et al. (04)
N3783: Reichert et al. (+94)
N7469: Wanders et al. (+97)
• Broad-emission line lags for objects
Kriss et al. (00)
• Including Hi & Lo ionization lines)
Collier et al. (+98)
N5548: Peterson et al. (02)
Krolik et al. (1991)
Peterson & Wandel. (+99)
Dietrich et al. (+93)
Korista et al. (+95)
N4151: Clavel et al. (+90) N3227: Winge et al. (+95)
Maoz et al. (+91)
Onken et al. (03)
Kaspi et al. (+96)
Shemmer et al. (04)
that also have infrared lags
(nucleus)
Reasons to pay attention to dust
2. Dust explains why Seyfert 2s exist
- obscuration of BLR as a function of orientation
- disappearance of BLR at low luminosity?
(Elitzur, related to wind; Laor related to inner radius)
N.B. Remember Ed Moran’s cautionary words regarding
incidence of hidden broad-line regions
- strong selection/sensitivity effects (but getting better)
- absence of evidence  evidence of absence
- lack of x-ray absorption is not diagnostic
Reasons to pay attention to dust
3. It’s an essential part of the NLR
- radiation pressure on dust determines ionization
structure? (Groves)
(complications: star formation, jets - Bennert, Holt, Inskip)
4. It’s an important constraint on early star formation
associated with AGNs (Hamann)
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Ways to probe dust in AGNs
1. IR Spectroscopic features (A. Lee, Sturm, Hao, Deo poster…)
- 9.7 m feature
- PAHs
Mid-IR average spectra
(Brandl et al., 2006)
L. Hao talk
Ways to probe dust in AGNs
1. IR Spectroscopic features (A. Lee, Sturm, Hao, Deo poster…)
- 9.7 m feature
- PAHs
2. XAFS in x-ray spectra (J. Lee)
3. Extinction/reddening law (Czerny) !!!!
4. Unification tests
- Radio galaxies & quasars (Cleary, Lal, Schulz poster)
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What Dust Cannot Explain
1. The X-ray absorber in Seyfert 1s
- x-ray absorber  infrared absorber (Elitzur, …)
- located on scale similar to BLR (Maiolino);
mid-IR emission much more extended
- selection effects an issue at high NH
Opportunities for study:
- time-variability (Risaliti)
- “fossil” reflection (Maiolino)
- XRB constraints for Compton-thick sources
What Dust Cannot Explain
2. Differences between Seyferts and LINERs
- amazing dichotomy in BPT diagrams! (Groves)
Sweet Separation
Groves, Heckman & Kauffmann (2006)
Kewley, Groves et al. (2006)
Brent Groves -NLR Models
What Dust Cannot Explain
2. Differences between Seyferts and LINERs
- amazing dichotomy in BPT diagrams! (Groves)
- probable explanation: different SEDs (Ho)
- SEDs really are different - lack of blue bump in LINERs
not extinction
- see some LINERs as UV sources (Elitzur quoting Maoz)
- at low z, MBH different (Constantin, Greene)
- low L/Ledd  ADAF or RIAF in LINERs
What Dust Cannot Explain
2. Differences between Seyferts and LINERs
- amazing dichotomy in BPT diagrams! (Groves)
- probable explanation: different SEDs (Ho)
- SEDs really are different - lack of blue bump in LINERs
not extinction
- see some LINERs as UV sources (Elitzur quoting Maoz)
- at low z, MBH different (Constantin, Greene)
- low L/Ledd  ADAF or RIAF in LINERs
Tools to probe excitation/energetics:
- X-ray (Marquez) - point sources in many cases, not always
- IR lines (Chary, Rupke) **
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Other New Things
1. A new composite QSO spectrum (Shang)
Results 1 of 3: Spectral Energy Distributions
Our sub-sample of 15 objects:
• Composite spectrum
(UV + optical + mid-IR)
• Normalized at 5600 Å
• Clear Silicates features
around 10 and 18 µm
• Near-IR composite spectrum
(Glikman et al. 2006)
• 27 AGNs (z<0.4)
• 1 micron inflexion
Other New Things
1. A new composite QSO spectrum (Shang)
2. Clustering constraint on Seyfert companions (C. Li)
C. Li talk
Other New Things
1. A new composite QSO spectrum (Shang)
2. Clustering constraint on Seyfert companions (C. Li)
3. High-velocity HI absorption wings - tracer of feedback
(Morganti)
4. Do star formation indicators break down in presence
of luminous AGN? E.g. [OII], PAHs (Levenson)
5. IMF on small scales may be skewed to high masses
(Nayakshin) - does this remove observable signatures
for t  108 yrs? (Cf. Sarzi)
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Other New Things
6. New metallicity diagnostics for the NLR (Nagao)
7. M-sigma deviations at z=0.37 (Malkan)
8. New tidal disruption candidates (Gezari)
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Homework: A to-do list
1. Clean up statistics on Sey 1/Sey 2 incidence ?
(Elitzur, Martinez-Sansigre)
(Moshe: “Clumpy unification becomes an issue of probability”)
N.B. don’t expect ratios to be same in Optical and X-ray
Clumpy Unification
Nc() = N0 exp(-2/2)
AGN type is a viewingdependent probability!
 Type 1 sources from “type
2 viewing”, and vice versa
 Flips between type 1 & 2
(Aretxaga et al 99)
 f2 variations may arise
from either  or N0 or both
f2 depends on both  and N0!
A to-do list
1. Clean up statistics on Sey 1/Sey 2 incidence ?
(Moshe: “Clumpy unification becomes an issue of probability”)
2. Revisit X-ray absorption vs. Luminosity? (J.X. Wang)
3. Figure out why bars are associated with higher x-ray NH
(Maiolino)
4. Be worried about studies that use jet axis as an indicator
of torus/disk axis (Jaffe)
Jaffe talk - NGC 1068
A to-do list
1. Clean up statistics on Sey 1/Sey 2 incidence ?
(Moshe: “Clumpy unification becomes an issue of probability”)
2. Revisit X-ray absorption vs. Luminosity? (J.X. Wang)
3. Figure out why bars are associated with higher x-ray NH
(Maiolino)
4. Be worried about studies that use jet axis as an indicator
of torus/disk axis (Jaffe)
5. Find more objects suitable for time-variability studies of
x-ray absorption (Risaliti)
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A to-do list (continued)
6. Start thinking about consequences of reflection of optical
light from torus (Gaskell)
7. Worry more about aperture effects (Jaffe, Sturm, Prieto, …)
8. Gain some more insight into extinction/reddening law !
9. Look for time variability in Si 9.7 m feature (Gaskell/Ogle)
•
Measure metallicities in high-z, low-L AGNs to address
evolutionary issues (Nagao)
A to-do list (continued)
11.Start thinking time-domain science (LSST, EXIST) and other
opportunities with new missions
Last but not Least:
Make plans to visit China again!
-The End-