active galactic nuclei fueling and...
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Active Galactic Nuclei Fueling and Obscuration
Jonathan Trump (Arizona)[email protected]
Probing the lower limits of nuclear activity with COSMOS
Advisor: Chris Impey (AZ)Other collaborators: Yoshi Taniguchi (Ehime), Brandon Kelly, Martin Elvis (CfA), Marcella Brusa (Max-Planck), Pat McCarthy (Carnegie),
Mara Salvato, Nick Scoville (Caltech)
Supermassive Black Holes
• Ubiquitous• Cycles of activity
– Active: AGN– Passive, like Sag A*
in our Milky Way• May be obscured
by gas/dust– From host galaxy?– Or local to AGN?
• Key role in galaxy evolution
SMBH – Host Galaxy Connection
Host regulates SMBH accretion?
SMBH regulates star formation in host galaxy?
• Tight relation between MBH and Mbulge / Lbulge
• Suggests that SMBH & host are connected
from Ferrarese et al. 2006
The Historical AGN “Unified Model”
Orientation explains:• QSO/Seyfert• Obscuration• Type 1 (BL) / Type 2
(NL)• Radio emissionBut some models (e.g.,
Hopkins et al. 2006; Nenkova et al. 2008) produce all these without orientation
from Urry & Padovani 1995
AGN Questions
• What sets the episodes of activity?– Fueling source
• Merger (Taniguchi 1999, di Matteo et al. 2005)• Stochastic disk (Hopkins & Hernquist 2006)
– Accretion rate– Black hole mass
• What causes obscuration?– Geometry– Host galaxy– Accretion rate / Luminosity / Mass
COSMOS AGN survey• Faint
– IMACS spectroscopy is 4 magnitudes fainter than main SDSS sample
– Smaller Black Holes (MBH ~ 107Msun at z>1)• Obscured
– X-ray, radio, and IR selection– Obscured evolution to z~1
• Rare populations– X-ray bright, optically normal galaxies
• Complete SEDs– Bolometric luminosities
• Higher Redshift– Host morphologies, environments & obscured types to z~1
Photometry• VLA 1.4 GHz (Schinnerer) – 7 μJy• Spitzer-IRAC 3-8 μm (Sanders) – 10 μJy• Spitzer-MIPS 24 µm (Sanders) – 15 mJy• HST-ACS (Scoville) – iAB~27• Subaru (Taniguchi) – mAB~27, 20 broad & narrow bands to mAB ~ 26• GALEX N/F UV (Schiminovich) – mAB~26• XMM (Hasinger) 0.5-10 keV – 8x1016 cgs• Chandra (Elvis) 0.5-8 keV – 2x1016 cgs
Spectroscopy• VLT/VIMOS (Lilly) – 10,000+ galaxies to iAB<26• Magellan/IMACS (Trump/Impey) – 1000+ AGN to iAB<23
COSMOS Multiwavelength Data
COSMOS Sensitivity to AGN SEDs
~40 times fainter than the typical SDSS quasar
Sensitive to QSO/Seyfert boundary at z~2
IRAC/MIPS for detecting heavily obscured AGN
SDSS SED, z~1.5(Richards et al. 2007)
Arp 220, z~1.5 (Silva 1998)
COSMOS AGN by X-rays
Chandra
The Spectroscopy
Magellan/IMACS to i<23 over 4 years
Nod & Shuffle
Supplementary MMT/Hectospec for additional blue spectral coverage
1569 spectra, incl. 540 X-ray AGN so far…
Unobscured to Obscured Ratio
At z<1:
Obscuration decreases with luminosity (3.6σ)
Obscuration increases with redshift 2.4σ)
Fit using logistic regression
Obscuration with Luminosity
• Trim down the accretion disk
• Push out the dust sublimation radius
• Blow out the star-forming host gas
Lawrence & Elvis 1982, Simpson 2005, Ballantyne 2008
Obscuration with Redshift
The redshift evolution of obscured AGN matches the evolution of star formation
Gas & dust associated with star formation plays a key role in AGN obscuration!
Barger et al. 2005, Ballantyne et al. 2008
Cosmic star formation history, from Hopkins 2004
Increases to z~1
Measuring Black Hole Mass
• Type 1 AGN: MBH ~ L0.5 × vfwhm2
• Calibrated from reverberation mapping of ~30 local AGN
• Virial theorem: MBH ~ RBLRvBLR
2
• RBLR~L0.5 (Kaspi et al. 2000, 07): scaling relations
Smaller Type 1 AGN
MBH ~ L0.5 × vfwhm2 (Vestergaard & Peterson 2006, 2009)
182 Type 1 AGN from COSMOS
Smaller black holes than, e.g., SDSS: z>1 Sag A* analogs
SDSS AGN (Kelly 08)
Typical error
AGN Fueling
• Type 1 AGN limited by L/LEdd > 0.01• L/LEdd increases with optical luminosity
AGN Fueling
• At L/LEdd<0.01, the BLR vanishes– Obscured by clumpy torus (Nenkova et al. 08)– Accretion disk changes (Hopkins et al. 08)
• L/LEdd increases with optical luminosity (4.8σ significance)– As L/LEdd, increases, more luminosity comes
from the (cool) accretion disk– At low L/LEdd, more luminosity is in (hot) X-rays
Optically Dull AGN
• Bright AGN in X-rays, but no emission lines in optical spectra
• 50 in COSMOS
• Distinct blue AGN continuum in optical…
• 70% have normal fX/fO!• 4 are variable!
Optically Dull AGN• Possible explanations for missing optical light
– Normal AGN, diluted by host (Caccianiga 07)
Optically Dull AGN• Possible explanations for missing optical light
– Normal AGN in bright host (Caccianiga 07)– Compton-thick nuclear absorption (Comastri 02)– Compton-thin host absorption (Rigby 06)
IRAC color-colorOptically dull AGN lack the hot IR color of Type 1/2 AGN
Optically dull AGN are not Compton-thick
Optically Dull AGN• Possible explanations for missing optical light
– Normal AGN in bright host (Caccianiga 07)– Compton-thick nuclear absorption (Comastri 02)– Compton-thin host absorption (Rigby 06)– Truncated accretion disk (RIAF, Yuan & Narayan 04)
Optically Dull AGN
• Explanations for missing optical light:– Normal AGN in bright host (Caccianiga 07)
• Works for optically dull AGN with normal fX/fO, 70% of the COSMOS sample
– Nuclear absorption (Comastri 02, Civano 07)• No evidence for hot IR dust• Not Compton-thick
– Host galaxy absorption (Rigby 06)• Variability on year timescales• No evidence for edge-on preference of hosts
– Truncated accretion disk (Yuan & Narayan 04)• Explains 30% of optically dull AGN with high fX/fO
Conclusions
• Obscured AGN fraction increases to z~1– Obscuration from the host galaxy?– Less efficient fueling at z~1?
• Limiting accretion rate for a BLR, L/LEdd > 0.01– L/LEdd < 0.01 as naked Type 2’s?– Weakly fueled AGN can’t blow out accretion?
• Optically dull AGN as observed RIAFs?Still to come…• Bolometric luminosity function• Reverberation mapping campaign• Obscured / Unobscured from photo-z AGN