1. Subaru AO high-spatial-resolution IR K- and L-band search for buried dual AGNs in merging galaxies Masatoshi Imanishi ( 今西昌俊 ) NAOJ/Subaru Telescope Imanishi+14 ApJ 780 106

2. Gas-rich galaxy mergers common in the universe Simulation (Kazantzidis) HST image CDM galaxy formation:

3. Multiple SMBHs common in mergers SMBH mass bulge mass NASA bulge mass SMBH mass Gultekin+09 Supermassive blackhole （ SMBH ） ubiquitous at galaxy center Many dual AGNs expected, if SMBHs are active

4. Wang+09 ApJ 705 L76 Double-peaked optical emission lines ~1% (87 / 6780 z<0.15 type-2 AGN) Hβ [OIII] 4959 [OIII] 5007 Dual AGN outflow jet interaction Two discrete line emitting clouds See also Liu+10,11, Smith+10, Pilyugin+12, Ge+12,Barrows+13

5. Fu+11b ApJ 733 103 Follow-up of double-peaked lines objects ~30% （ 16/50 ） double nuclei Dual AGNs not required in the majority (~70%) （ Jet-cloud interaction etc ） 10” Keck II/OSIRIS+LGS-AO H-band

6. Very small (<1%) dual AGN fraction in double-peaked lines dual AGN search miss face-on SMBHs Edge-on:OK Face-on: undetectable Buried AGNs undetectable Need observations at wavelengths of low dust extinction

7. High-spatial-resolution imaging Sensitive to face-on multiple SMBH with small separation radio (VLBI) X-ray 2-10 keV (Chandra; 0.5”) Miss the majority of radio-quiet AGN Miss Compton-thick (N H > 10 24 cm -2 ) AGNs Burke-Spolaor11 Teng+05,09,12,Iwasawa+11a,11b, Koss+12,Liu+13

8. Our method: Subaru AO infrared imaging Infrared K (2.2um) and L’(3.8um) Subaru-AO (0.1-0.15”) Sensitive to buried AGNs, including radio-quiet ones Sensitive to small separation (face-on) dual AGNs at late merging stage

9. AKARI 2.5-5um spectroscopy Normal starbust Buried AGN PAH Imanishi+10 ApJ 721 1233 Starburst: K-L blue (~0.5 mag) Buried AGN: K-L red (~2 mag) (AGN heated hot dust emission)

10. AGN (red K-L nucleus) 28/29 (U)LIRGs show at least one AGN 10” Imanishi+14 ApJ 780 106

11. Dual AGNs (two red K-L nuclei) 10” Imanishi+14 ApJ 780 106 4/29 (U)LIRGs

12. Subaru AO L’(3.8um) (0.1-0.2”) Spitzer IRAC 3.6um (1”/pix) WISE 3.4um >5”

13. Small fraction (15%) of IR buried dual AGN 1. Dust obscuration ? 2. Orbiting geometry ? 3. Non-simultaneous SMBH activation

14. SMBH mass ratio between two nuclei AGN luminosity ratio between two nuclei Less massive SMBH has high Eddington ratio More massive SMBH is more actively mass accreting (=high Eddington ratio) Imanishi+14 ApJ 780 106

15. More massive SMBH has higher Eddington ratio Non-simultaneous SMBH activation throughout the merging phase Imanishi+14 ApJ 780 106

16. Our Infrared K- and L-band AO imaging revealed non-simultaneous SMBH activation Even if two SMBHs are present, only one SMBH can become sufficiently luminous to be detectable as an AGN Can explain the observed small dual AGN fraction in merging galaxies Summary More massive SMBHs have higher Eddington ratio

17. Summary 2 SMBH activation is dominated by local conditions, rather than global galaxy properties Difficult to predict by simulation Need observational constraints Imanishi+14 ApJ 780 106

18. End

19. Buried AGN L ν (3-4μm) (intrinsic) = L(AGN) ν