Image: C. Claver & N. Sharp (NOAO)

Double-Peaked Balmer Line Emission in Active Galactic Nuclei

Iskra Strateva, MPE

N.Brandt M.Eracleous J.Gunn P.Hall L.Hao Ž.Ivezić G.Knap S.Komossa K.Lewis Li-Xin Li R.Lupton B.Paczynski G.Richards D.Schlegel M.Strauss W.Voges N.Zakamska

Chen & Halpern 1989

October 2006 The Central Engine of AGN, Xi’an, China

Outline

• Optical/UV properties of double-peaked emitters (Eracleous+’94,’03, Strateva+’03, Wu & Liu’04)

• What can we learn about the accretion disk from Balmer line profile fits (Strateva+’07, in prep.)

• SWIFT/Chandra X-ray survey of FWHM>15000 km/s double-peaked emitters (Strateva+ ’07, in prep.)

October 2006 The Central Engine of AGN, Xi’an, China

Optical Properties of Double-Peaked Emitters

• 2-3% of z < 0.33 SDSS AGN (Strateva+03)

• Up to 20% of Broad Line Radio Galaxies (Eracleous+’94, ’03)

• Most FWHM >15000 km/s AGN

How common are they?

Optical/UV properties:

• Similar optical/UV luminosity

• 10-5 < L/LEdd < 0.1 (Lewis+’06)

• Broader low-ionization (H, H, MgII) lines

• Single-peaked high-ionization (CIII], CIV, Ly) lines (Halpern+’96, Eracleous+’04)

• Lower-ionizaion NLR (e.g. higher [OI]6300/[OIII]5007 ratios )

Halpern+’96

October 2006 The Central Engine of AGN, Xi’an, China

Using Double-Peaked Emitters to Study the Accretion Disk

disk inclinations: 20° < i < 60°

inner and outer radii: 200RG< 1 < 1000RG 1000RG< 2 < 4000RG

• Evidence for coplanar obscuring material

• Outer radii consistent with onset of disk self gravity

X-ray Spectra of Double-Peaked Emitters

•16 broadest double-peaked emitters with SWIFT and Chandra

•10 RL double-peaked emitters from the Eracleous et al. sample

•7 objects with serendipitous XMM/Chandra coverage Strateva+’06

•22 objects with serendipitous ROSAT coverage

October 2006 The Central Engine of AGN, Xi’an, China

External Illumination of the Accretion Disk

No! Based on 58 double-peaked emitters published by Eracleous+03, Strateva+06,and the new Chandra/SWIFT sample.

Is viscous dissipation of energy locally in the accretion disk sufficient to power lines of the observed strength?

Eracleous+’03; Strateva+’06

October 2006 The Central Engine of AGN, Xi’an, China

X-Ray Properties of Double-Peaked Emitters: II

• Steeper ox at comparable 2500Å luminosity (Strateva+’06, Strateva+’07, in prep.)

See also Wu & Liu’04October 2006 The Central Engine of AGN, Xi’an, China

Summary

•2-3% of optically selected AGN have double-peaked emission lines consistent with origin in the accretion disk; fully 1/5th of BLRGs and most FWHM>15000km/s AGN do

•External illumination is necessary to produce lines of the observed strength

•Not always low accretion-rate, low-luminosity AGN

•Accretion disk emission from few x100RG and outer radii consistent with the onset of gravitational instability (2000-4000RG); flatter disk emissivity profiles than simple point source; evidence for coplanar obscuring material

• Double-peaked emitters are on average X-ray brighter than similar UV luminosity AGN

• Intrinsic X-ray obscuration of 5x1020-1022 cm-2 in 8 of the 16 sources

October 2006 The Central Engine of AGN, Xi’an, China