active galactic nuclei
DESCRIPTION
Active Galactic Nuclei. IUE. Swift. Paul O’Brien X-ray & Observational Astronomy Group University of Leicester Previously at: University College London [PhD, UCL 1987: A study of the UV continuum of quasars] IUE Project, UCL/RAL University of Oxford University of Leicester - PowerPoint PPT PresentationTRANSCRIPT
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STFC Summer School 2007
Paul O’BrienX-ray & Observational Astronomy Group
University of Leicester
Previously at: University College London
[PhD, UCL 1987: A study of the UV continuum of quasars]
IUE Project, UCL/RAL
University of Oxford
University of Leicester XMM-Newton, Faulkes Telescopes & Swift
Active Galactic NucleiIUEIUE SwiftSwift
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Active Galactic Nuclei
• A little history
• Taxonomy (split them up)
• Unification (join them together again)
• Mass, size and structure
AGN: an object with nuclear, non-stellar energetic phenomena.
Power-source: accretion disc feeding a massive black hole.
But why, when, where, how…?
Radio mm IR Opt./UV X-ray
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STFC Summer School 2007
History lesson – start (almost) at the beginning
Leviathan, 1845, 1.8m telescope! Birr Castle, Parsonstown, Eire (wet)
Owned by Lord Rosse (optimist)
M51 – example of a “spiral nebula”
PhD student goes here
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STFC Summer School 2007
The first galaxy/AGN spectra
• Photography improved (dry plates) by late 1800s so could be used in a spectrograph stellar spectral classification (Pickering, Cannon etc.).
• Sir William Huggins, 1864 – spectroscopy of M31 (Andromeda). Saw (faint) absorption lines but unsure if they were reflected Moon-light
• Edward Fath, 1909 PhD – displayed nebulae spectra showing that galaxies look like stars – i.e. galaxies are made out of stars!
But, also found a galaxy (in 1908) that had: “bright lines in its spectrum, has also a strong continuous spectrum which contains absorption lines”.
Object: NGC1068 (M77) – the first AGN!
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STFC Summer School 2007
Seyfert Galaxies
• Fath followed by Slipher (M31 velocity), and Hubble…(fame, fortune?, telescope)
• Carl Seyfert (1943) – Postdoc at Mount Wilson
Isolated 6 spiral galaxies with blue nuclei which show “high-ionization emission lines much wider than absorption lines in normal galaxies”.
• Two basic types:
Seyfert 1 - broad permitted lines + narrow forbidden lines
Seyfert 2 - narrow permitted and forbidden lines H [OIII]
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STFC Summer School 2007
Example Seyfert spectra
Wavelength (Å)
HH
Blue continuum
Red continuum
HH
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STFC Summer School 2007
NGC 3783
See a large range in ionization species
(too large for normal nebulae)
Seyfert Type 1
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STFC Summer School 2007
Radio Galaxies
• Discovered after WWII (Ryle, Mills etc.)
• Example: M87 (NGC4486). Identified by Bolton, Stanley & Slee (1949). [Optical jet found by Curtis in 1918]
• Radio emission is non-thermal (Synchrotron. + Inverse Compton)
M87 optical
M87VLA
Quasars/QSOs
• 3C273 (Mararten Schmidt 1963).
• High redshift (0.158) implied huge luminosity. Also variable small size
• Most (~90%) are radio-quiet (QSOs).
• Quasars found in elliptical galaxies.
• QSOs found in either spirals or ellipticals.
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STFC Summer School 2007 The Host Galaxy and the AGN
galaxies at same redshift
Disturbed morphology
Interaction?
Disturbed morphology
Interaction?
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STFC Summer School 2007
Need to explain the diverse properties of AGN
• AGN can be very luminous (1000x bright galaxies)
• The continuum varies on (fairly) short timescale small objects
• Broad-band continuum + wide range in emission line ionisation
• See both “broad” (10000 km s-1) and “narrow” (2000 km s-1) emission lines. The narrow lines are broader than normal galactic lines.
Solution: the accreting supermassive black hole (SMBH) model…
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STFC Summer School 2007
Size-scales
Black-hole: Rs = 3x109 M6 m
Accretion disc: ~3 – 104 Rs
Broad Line Region: ~1-100 light-days
Molecular Torus: ~1-10 light-years
AGN Type 1 and 2 Unification
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STFC Summer School 2007
Type 1 AGN
Type 2 AGN
Radio loud AGN Obscuring stuff
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STFC Summer School 2007
Black holes in every galaxy?
M87 – ionized gas rotation curve.
Large dark mass required (~109 M
Virial theorem: M (r V 2 /G)Magorrian et al. 1998
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STFC Summer School 2007
MBH-* relationship
Reverberation
Other methods
Calibrate AGN method vs. stellar (Ferrarese). AGN follow same relation as in-active galaxies.
“Bulge” mass correlates with mass of SMBH
Peterson et al.
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STFC Summer School 2007
PDS 456 – the most powerful object in the local Universe, but unknown until 1997…
Torres et al. (1997); Yun et al. (2004)
At z=0.184, 1'' = 3.1 kpc
QSO Luminosity vs. redshift
Nearby galaxies Interaction?
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STFC Summer School 2007
X-ray spectrum requires a massive, highly-ionized outflow moving at ~0.15c . Also see fast outflow in the UV.
Outflow mass-loss rate ~ 10 M yr-1
For 10% covering factor, outflow K.E. ~ 1039 J s-1 (10% Lbol)
(Reeves et al. 2003; O’Brien et al. 2005)
X-ray and UV observations of PDS 456
CIV 1549 v -5000 km s-1
Ly/NV
Ly BAL (12-22000 km s-1)
PDS456 3C273
Massive absorption
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STFC Summer School 2007
• Some outflows have a K.E. comparable to the radiation luminosity: are they common in the early Universe?
• Most SMBH mass probably assembled by luminous accretion. So perhaps built when the accretion rate is high/spin low?
• Over ~107 years X-ray outflows could deposit a total mechanical energy comparable to the binding energy of a Galactic bulge (~1052 J).
• Feedback between outflows and star formation??
What could outflows mean – the concept of “feedback”
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STFC Summer School 2007
Interaction in action…the Ultraluminous IR Galaxies
IRAS revealed a large population of “Ultraluminous IR Galaxies”.
Star-formation rate 100-1000 xGalactic.
Most are interacting or highly disturbed.
SMBHs (and galaxies?) grow through accretion, SF, outflows all driven by mergers, shocks, galactic bars etc.
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STFC Summer School 2007
How do we see into the heart of an AGN ?
Try radio interferometry
e.g. M87 , only ~18Mpc away (1" ~ 300 light-years)
But, we need to look in the optical/IR
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STFC Summer School 2007
Magdalena Ridge Observatory, NM – 10 x 1.4m optical/IR telescopes with baselines up to 340m. On schedule for 2008/2009 start. Observe from 0.6-2.4 microns with spatial scale of 0.3-30 mas.
Creech-Eakman et al. 2006
VLTI – 4x8.2m + 4x1.8m Baselines up to 200m, ~10mas
Optical interferometry
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STFC Summer School 2007AGN – The Future
• More data of all kinds + better models
• Deep surveys in sub-mm, IR, X-ray, etc. to find all the AGN
• High-resolution imaging in radio, optical, IR (e.g. SKA, VLTI, MRO)
Time-dependent, 3-D, MHD disc(torus) simulation (Hawley et al.)
UK astronomers have UKAFF – the UK Astrophysics Fluids Facility at Leicester – build your own disc, jet, black hole…
Have fun!
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STFC Summer School 2007
The end