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Fluorescent Processes
Research School of Astronomy & Astrophysics
Feeding The Beast: Infall, Mergers or Starbursts?
Mike Dopita (ANU)
Research School of Astronomy & Astrophysics
Fluorescent Processes
Topics to be Covered:
What is the nature of “cooling flow Elliptical Galaxies”?
How do Luminous IR galaxies (LIRGS) evolve and feed their Black Holes?
What can we learn from IR spectroscopy of LIRGS?
How do AGNs feed back on their hosts in the hi-Z Universe? (the revenge of the AGNs!)
How do starbursts blow winds? (the revenge of the massive stars!)
Fluorescent Processes
Research School of Astronomy & Astrophysics
1. “Cooling Flow” Elliptical Galaxies
collaborators
Catherine Farage ANU (Thesis Project),
Peter McGregor ANU
Research School of Astronomy & Astrophysics
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“Cooling flows”
According to the Fabian/Nulsen model, the hot X-ray emitting plasma in Elliptical Galaxies cools and falls into the galactic core, feeding the supermassive Black Hole.
Is this model correct?
Consider first the southern “poster child” of cooling flows, NGC 4696...
Research School of Astronomy & Astrophysics
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NGC4696 (Crawford 2005)
Research School of Astronomy & Astrophysics
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NGC4696 (Crawford 2005)
Note close correlation of X-ray and H-
alpha
Research School of Astronomy & Astrophysics
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NGC4696 (Crawford 2005)
Note close correlation of X-ray and H-
alpha
Radio emission
morphology is determined by gas, not vice-
versa.
Research School of Astronomy & Astrophysics
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NGC4696 (Crawford 2005)
Note close correlation of X-ray and H-
alpha
Radio emission
morphology is determined by gas, not vice-
versa.
Where would dust come from in a
cooling flow?
Research School of Astronomy & Astrophysics
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..so, make WiFeS Observations of NGC 4696
Farage, Dopita & McGregor
B 7000
R 7000
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[N II] Brightness Distribution
(note strong central concentration)
Research School of Astronomy & Astrophysics
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[N II] Velocity Dispersion
(note low velocity dispersion)
[N II] Velocity Centroid
(note evidence for rotation)
Research School of Astronomy & Astrophysics
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Research School of Astronomy & Astrophysics
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LINER spectrum. Strong [NII] and [N I] and weak [O III]] imply low shock velocities ~ 80km/s
Compare with the Herbig-Haro
spectrum of DG Tau
Research School of Astronomy & Astrophysics
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Conclusion on NGC 4696
The presence of dust implies we see matter from a minor merger, not a cooling flow. This is supported by:
Rotational support rather than infall
Low velocity dispersion in filaments
“Liner” Spectrum characteristic of low velocity (<100km/s) shocks.
Research School of Astronomy & Astrophysics
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A much larger and more luminous source: Abell 2204
Research School of Astronomy & Astrophysics
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Research School of Astronomy & Astrophysics
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..again, a LINER spectrum. Strong [NII] very strong [N I] and weak [O III]] again
imply low shock velocities, despite a much larger total velocity dispersion.
Research School of Astronomy & Astrophysics
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If either shocks or cooling flows, the X-ray is too strong for the observed H-alpha in
emission line radio E galaxies
T = 5E5 K T =2.5E6 K
Research School of Astronomy & Astrophysics
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A Dynamical Model:Fragments of merger orbit through hot halo gas,
and are shocked as a result.
T ; c0
1 T
0
n0
Vorb Vs
nc
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Implications of this “Heating Flow” model:
Orbital Motion is transonic (weak shocks):
Ram pressure drives cloud shock:
Some likely parameters of the problem:
Therefore we have:
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2. Luminous IR Galaxy MergerscollaboratorsJeff Rich IFA, Hawaii (Thesis Project), Lisa Kewley & Dave
Sanders IFA, HawaiiLee Armus Spitzer Science Center
and the GOALS team
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GOALS: Merging IR-Luminous Galaxies in the local Universe
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IRAS 18293-3413
He I + Na I [S II]
H-alpha + [N II]
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Galaxy Image
Velocity Field
H-Alpha Image
Line Ratio Map
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The Merger ScenarioSanders & Mirabel (1996); Banes & Hernquist (1996) etc.
Starburst Phase
First Passage: Formation of Tidal Tails
Research School of Astronomy & Astrophysics
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The Merger ScenarioSanders & Mirabel (1996); Banes & Hernquist (1996) etc.
First Passage: Formation of Tidal Tails
Second Passage & Merging Phase
AGN Phase
Starburst Phase
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The Merger ScenarioSanders & Mirabel (1996); Banes & Hernquist (1996) etc.
First Passage: Formation of Tidal Tails
Second Passage & Merging Phase
Abundance GradientsNormal
Abundance GradientsDisrupted
Abundance GradientsDisrupted
Abundance GradientsDisrupted
Abundance Gradients Mixed, gas flows lower nuclear abundance
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Gas flows from Abundance Measurements:Kewley Geller & Barton 2006, AJ, 131,2004
Nuclear Abundance Lower in Merging Galaxies:Implies Gas flows to nucleus
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Gas flows from Abundance Measurements:Kewley Geller & Barton 2006, AJ, 131,2004
..and Abundance Gradientis disrupted
Nuclear Abundance Lower in Merging Galaxies:Implies Gas flows to nucleus
(Keck LRIS Spectroscopy)
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Amount of Gas Inflow to Nucleus in Mergers
Assuming gas inflow ~7 M_sun/yr
and an initially normal metallicity gradient
We need 50-60% dilution in nucleus
c.f. Merger models, which predict 60%
and we need an infall timescale of 10-100 Myr
c.f. merger models, which predict 100 Myr.
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Excitation Conditions
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Spectral Classification: Yuan, Kewley & Sanders (2009)
IRGs
LIRGs
ULIRGs
logL>8
logL >12
10.5<logL <12
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Old Classifications:
Veilleux et al. (2005)
Sy 2
Sy 1
LINER
HII
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New Classifications:
HII
Sy 2
Sy 1
Comp
Amb
Yuan, Kewley & Sanders (2009)
Note how Seyfert activity is at first hidden, then becomes dominant both at late phases and in ULIRGs
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What is the Nature of Transition Objects?
Do all (or any of) the transition objects contain an AGN?
For: Their line ratios are shifted in the direction of AGN.
Against: No radio point sources are detected in these objects.
Could this be the result of high free-free optical depth in the radio?
Answer: Only if surface rate of SF is rather extreme, or if the AGN has a very strong ionized wind.
If so, why are the ULIRGS more LINER-like than Seyfert II -like?
Could this indicate a role for distributed shock emission?
Could the IMF in these objects be unusually flat?
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3. Infrared Modelling of LIRGS
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Analytic Modelling (Dopita et al. 2004-8)
Use STARBURST 99 to provide the intrinsic stellar SEDs.
Use MAPPINGS IIIq to compute HII region temperature, ionisation, emission line spectrum, dust and PAH absorption, dust re-emission in the mid- and far-IR.
Dust model includes grain shattering size spectrum, quantum fluctuations of the dust temperature & PAH photodissociation.
Ensure that any cluster of a given age is placed in its self-consistent evolving HII region.
Add the contribution of the old (10-100Myr) stars.
Put the whole lot behind a dusty turbulent foreground screen.
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Our Model Starburst: HII Regions of all ages and many cluster masses evolve in an ISM of a given pressure & chemical abundance
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Fits to SEDs of “template” starburst galaxies.
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Fits to SEDs of “template” starburst galaxies...Pretty good!
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GOALS IRS Sample (Armus et al.)
log C = 5.5A(v) = 8 mag
A(v) = 19 mag A(v) = 31 mag log C = 5.5log C = 5.5
A(v) = 0 mag log C = 5.5
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AGN +SB in GOALS Sample (Armus et al.)
PAH Class C emission?see Tielens 2008, ARAA
NLR dominated
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..curiously enough, only 15-20% have AGN!
PAH Class C emission?see Tielens 2008, ARAA
NLR dominated
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GOALS Sample - Silicate Absorption
A(v) = 60 mag; SFR = 60
A(v) = 56 mag; SFR = 65
Draine “Astronomical” Silicate Opacity does not give a good fit
to the 10 and 18 µm Si absorption.The 18 µm Si absorption is too weak,
and the central wavelength of the 10 µm feature is too short.
Fluorescent ProcessesResearch School of Astronomy & Astrophysics
24 µm
18.4 µm
10.0 µm
9.3 µm
18.0 µm
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...due to larger grain size (~1.5 µm) in the starburst region
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4. Radio Galaxy AGN Feedback(the revenge of the AGN)
- Expelling the Interstellar Gas
- The Transition to “red-and-dead”
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Research School of Astronomy & Astrophysics
QuickTime™ and aGraphics decompressor
are needed to see this picture.
The Evolution of a Radio Galaxy(Model by Sutherland)
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ACS Observations,Box: 2x2 arc sec. ~ 16x16 kpc
Scale 0.05 arc sec/ pixel ~ 400 pc
CIII] 1937Å
CIII] 1937ÅCIII] 1937Å
1513Å 1513Å
1513Å
[O III] Galaxies around Radio Galaxy MRC 0316-257 (z=3.13)
Maschietto et al. 2008 MNRAS
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Example: 4C 41.17Universe: 1.6 Gyr old
Data By: van Breugel et al 2002
low freq.radio jet
Feedback by AGNJet Interaction
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Research School of Astronomy & Astrophysics
..forming stars at the rate of 5000 solar masses per year!
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..with shock excited jet emission
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Ly−α and H−α 1138-262in PKS( , , , & , 2003)Kurk Pentericci Röttgering Miley Heckman
Jet Hot-spot
Colour: Ly−αContours: H−α
Nucleus
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Ly-Alpha Halos associated with Hi-z Radio Galaxies are:
Luminous: F = 10-15 erg s-1 cm-2 or L = 1044 erg sec-1 &
Large: up to 200 kpc across or ~ 20 arc sec in diameter!
Over 400 candidates remain unstudied.
These Galaxies both represent truly galaxy-wide starbursts with chemical enrichment and “maximal” star formation extending over some 10-100 kpc2.
Such galaxies (and their radio-quiet counterparts) probably represent the dominant mode of star formation in the Universe at 4 > z > 2, forming typically 300-3000 solar masses per year.
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The Expanding Shell of 4C 60.07:Evidence for AGN Feedback
Reuland et al. 2006 AJ
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4. Galactic Winds and Fountains (the
revenge of the stars)
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The Prototypical Superwind - M82 Chandra, HST, Spitzerhttp://chandra.harvard.edu/photo/2006/m82/m82_comp.jpg
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Condition to drive a Galactic WindWe need (at least) that the kinetic energy injection per unit area into a fraction of the disk gas will exceed its binding energy:
Star formation follows the Kennicutt (1998) Law:
So a wind becomes possible when:
Therefore, a wind is driven when:
Escape Velocity is Low (i.e. galaxy is small)Lifetime of Starburst is longGas surface density is high
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Structure of a Superwind
Cooper, Bicknell & Sutherland, RSAA: astro-ph 0710.5437
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The Movie of a Superwind
QuickTime™ and aYUV420 codec decompressor
are needed to see this picture.
Cooper, Bicknell & Sutherland, 2008
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Conclusions: Winds & Fountains
Galactic winds can be driven when the collective effects of disk star formation become important, i.e. when hot bubbles can collide & merge in the halo.
Starburst winds are driven when the star formation is of high concentration, long continued, and when the depth of the galaxian potential is sufficiently shallow.
These conditions may be mutually exclusive, but are generally favoured in merging starburst galaxies.
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That’s All Folks!!