Active Galactic Nuclei Fueling and Obscuration

Jonathan Trump (Arizona)jtrump@as.arizona.edu

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