1. Compact nuclear starburst in the central regions of Seyfert galaxies K. Kohno University of Tokyo “The Central Engine of Active Galactic Nuclei” October 20, 2006 Xi’an, China

2. Outline Introduction: Roles of dense molecular medium in active galaxies The survey CO(1-0), HCN(1-0), and & HCO+(1-0) high resolution imaging survey of Seyfert and starburst galaxies using Nobeyama Millimeter Array & RAINBOW interferometer Results HCN/HCO+ & HCN/CO ratios diagram as a new diagnostics of power source in active galaxies Discussion Comparison with diagnostics at other wavelengths Application to LIRGs/ULIRGs Application to southern galaxies using ASTE/ATCA

3. Collaborators T. Shibatsuka, K. Nakanishi, M. Imanishi, T. Tosaki, S. Ishizuki, S. Matsushita, M. Okiura, K. Sorai, S. Onodera, A. Doi, H. Nakanishi, Y. Sofue, S. K. Okumura, B. Vila-Vilaro, T. Okuda, K. Muraoka, A. Endo, B. Hatsukade, R. Kawabe Univ. of Tokyo NAOJ Hokkaido Univ. Yamaguchi Univ.

4. Results Introduction

5. Roles of Dense molecular gas in the centers of active galaxies AGN Dense Molecular Gas Starburst ? Starburst – AGN connection Fueling Obscuration Jet/outflow Radiation (hard) Fueling SNe/outflow Radiation (soft) Obscuring torus consists of dense molecular gas; can be a diagnostic tool as well Stars are formed from dense molecular cores ⇒ AGN – starburst connection

6. How to trace dense molecular gas High-J CO lines Large A-coeff., large statistical weight g J  tracer of dense (and warm) molecular gas using submillimeter single dishes: JCMT, CSO, HHT, ASTE, APEX SMA: an ideal tool before ALMA High dipole moment molecules such as HCN, HCO+, CS, etc. ⇒ using millimeter interferometers NMA+RAINBOW/PdBI/OVRO/BIMA/ATCA

7. Results Dense gas in Seyfert and starburst galaxies

8. NMA/RAINBOW 3D imaging survey of dense molecular gas toward local AGN/SBs 20 Seyferts (6 Sy1s and 14 Sy2s) and 12 starburst galaxies Mainly from Palomar Seyfert sample (Ho et al. 1997) High resolution (1.6 – 8.6 arcsec) imaging-spectroscopy of HCN(1-0), HCO + (1-0) : tracers of dense molecular medium CO(1-0) : tracer of total molecular gas as a NMA long-term project: 2003-2006 (+ Observatory program) The mission completed! RAINBOW: 7-element interferometry (cross correlations among six 10 m dishes & one 45 m)

9. The Seyfert sample Mainly from 「 Palomar Seyfert Sample 」 Ho & Ulvestad 2001, ApJS, 133, 77 Based on systematic spectroscopic search for AGNs (cf. CfA sample etc.) Nearby (D < 70 Mpc), 52 Seyferts (11 Sy1s, 41 Sy2s) NMA/RAINBOW survey sample 15 Seyferts in CO (1/4 of the whole sample) from Palomar Seyfert sample ＋ some additional Southern Seyferts NGC 1097, NGC 5135, NGC 6764, NGC7465, NGC 7469

10. Observed Seyfert galaxies Sy1s COHCNHCO+ N1097 ○○○ N3227 ○○○ N4051 ○○○ N5033 ○○○ N5548 ▽▽▽ N7469 ○○○ Sy2s COHCNHCO+ N1068 (○)(○) ○○ N1667 ○ N3079 ○○○ N3982 ○ ×× N4258 ○○○ N4388 ○○○ N4501 ○○○ N4579 ○ N5135 ○ N5194 ○○○ N6764 ○○○ N6951 ○○○ N7465 ○ ×× N7479 ○○○ ○ ： completed ▽： in progress × ： non detection 19 CO images 15 HCN & HCO+ images

11. Nobeyama CO(1-0) Atlas: type-1 Seyferts 1 kpc NGC 7469 NGC 1097: Kohno et al. 2003, PASJ, 55, L1 NGC 5033: Kohno et al. 2003, PASJ, 55, 103 NGC 7469: Okiura et al. 2007, in prep. Other galaxies: Kohno et al. 2007, in prep.

12. Nobeyama CO(1-0) atlas: type-2 Seyferts 1 kpc NGC 3079: Koda et al. 2002, ApJ, 573, 105 NGC 4501: Onodera et al. 2004, PASJ, 56, 439 NGC 6951: Kohno et al. 1999, ApJ, 511, 157 Other galaxies: Kohno et al. 2007, in prep. NGC 4501

13. Observed Starburst galaxies nearby galaxies (D < 20 Mpc) nuclear starburst and evolved starburst galaxies Also many of them are in the Ho et al.’s catalogue Non-Sys COHCNHCO+ Maffei2OOO IC 342OOO N253OO* M82OOO N3504OO* N3627OOO N3628OOO N4527OOO N4736OO M83OOO N5195OOO N6946OOO O : completed * ： in progress

14. CO, HCN, HCO+ Images of Seyferts

15. NGC 1097 Nucleus ： R HCN/CO = 0.39 R HCN/HCO+ = 1.9  significant enhancement of HCN, any other causes other than high gas density ?

16. Nucleus ： R HCN/CO = 0.56 R HCN/HCO+ = 2.5 Similar critical density (n H2 >10 4 H 2 /cm -3 ) Similar optical depth (tau>>1) ⇒ difference of abundance (filling factor) NGC 5194 Sakamoto et al. 1999

17. NGC 1068 Nucleus ： R HCN/CO = 0.54 R HCN/HCO+ = 2.1  significant enhancement of HCN Disk ： R HCN/CO = 0.10 R HCN/HCO+ = 1.3  typical values for starburst regions Helfer & Blitz 1995

18. The 4 th HCN enhanced Seyfert: NGC 5033 HCN and HCO+: central concentration, contrary to CO R HCN/CO = 0.23, R HCN/HCO+ = 1.9  This is the 4 th “NGC 1068”, i.e., HCN enhanced Seyfert nuclei. 4.3±0.63 Jy/b km/s2.3±0.63 Jy/b km/s31±2 Jy/b km/s Flux at the nucleus:

19. New results: enhanced HCN in NGC 4501 1kpc CO(1-0) HCN(1-0) this work CO: Onodera et al. 2004, PASJ, 56, 439

20. NGC 4501: the 5 th HCN-enhanced Sy “the 5 th NGC 1068” CO: 74 Jy/b km/s HCN: 5.4 Jy/b km/s HCO + : 2.9 Jy/b km/s → R(HCN/HCO + )=1.8 R(HCN/CO)=0.12 By S. Onodera

21. NGC 4388 ： possibly the 6 th example

22. “HCN enhanced Seyfert nuclei”: currently 6 galaxies are identified High angular resolution HCN observations of Seyferts NGC 1068 (Sy 1.8) ： Jackson et al. 1993 (NMA), Tacconi et al. 1994 (PdBI), Helfer & Blitz 1995 (BIMA) NGC 5194 (Sy 2) ： Kohno et al. 1996, ApJ, 461, L29 (NMA) NGC 1097 (Sy 1) ： Kohno et al. 2003, PASJ, 55, L1 (NMA) NGC 5033 (Sy 1.5) ： Kohno et al. 2005, astro-ph/0508420 (NMA) NGC 4501 (Sy 2) & NGC 4388 (Sy 2) also (this work)

23. Question HCN enhancement: what is this ? Related to star formation, as seen in starburst galaxies ? Star formation – HCN luminosity correlation (Solomon et al. 1992, Gao & Solomon 2004a, 2004b) Spatial correlation between HCN and star formation (Kohno et al. 1999, ApJ, 511, 157) or.. ? How about other Seyferts ?

24. NGC 3227: no HCN enhancement R HCN/CO = 0.043 R HCN/HCO+ = 0.79 Nuclear HCN source is very compact (~ a few 10 pc scale; Schinnerer et al. 2000, ApJ, 533, 826)

25. NGC 3079 Nucleus ： R HCN/CO = 0.11 R HCN/HCO+ = 1.3  Within typical values for starburst regions Rather extended HCO + ?

26. R HCN/CO = 0.14; R HCN/HCO+ = 0.63 Radio bubble (Hota & Saikia 2006) NGC6764: no enhancement

27. NGC 7469 R(HCN/CO) = 0.20 R(HCN/HCO+) = 0.80 → “composite” AGN PAH ？： No → “pure” AGN Imanishi & Wada 2004, ApJ, 631, 163 Difference on line profiles?  difference of spatial distribution?

28. NGC 7479 No HCN enhancement.

29. NGC 3982 Non-detection R HCN/CO < 0.33

30. NGC 7465 Non- detection R HCN/CO < 0.18

31. HCN & HCO + Images of Starburst Galaxies 200 pc NGC 6946 IC342 NGC 3628 NGC 3627 Maffei2 HCN HCO+ HCN HCO+

32. Results Summary of results: Line ratios

33. Seyfert vs Starburst: histogram of R HCN/CO Starburst: R HCN/CO < 0.3 Seyfert: enhanced R HCN/CO (>0.3), which are never observed in SBs Note: R HCN/CO depend on spatial resolution (CO distribution) R HCN/CO Number Starburst Seyfert

34. Seyfert vs Starburst: histogram of R HCN/HCO+ R HCN/HCO+ Number Starburst Seyfert Starburst: R HCN/HCO+ < 1.5 Seyfert: enhanced R HCN/HCO+ (>1.5), never observed in SBs Tracing dense part of gas  less sensitive to extended diffuse gas

35. HCN/HCO+ & HCN/CO ratios: Seyfert galaxies vs starburst galaxies Seyfert Starburst R HCN/CO R HCN/HCO+

36. Difference on dominant power sources within observing aperture beam Seyfert Starburst R HCN/CO R HCN/HCO+ “Pure AGN”: X-ray irradiated dense molecular gas, i.e., XDRs “Composite”: AGN with a nuclear starburst

37. HCN/HCO+ abundance: PDR vs XDR HCN is overabundance relative to HCO+ in XDRs Opposite sense in PDRs Meijerink & Spaans 2005, A&A, 436, 397; see also Maloney et al. 1996, ApJ, 466, 561; Lepp & Dalgarno, 1996, A&A, 306, L21 PDR XDR

38. “pure” vs “composite” Seyferts Seyfert nucleus X-ray irradiated dense molecular gas (XDR) Starbursting dense molecular gas (PDR)

39. “pure” vs “composite” Seyferts: effect of aperture size (observing beam) Seyfert nucleus Identified as 「 composite Seyferts 」 e.g. NGC 3079, 3227, 4051, 6764 etc X-ray irradiated dense molecular gas (XDR) Starbursting dense molecular gas (PDR) Observing beam

40. “pure” vs “composite” Seyferts: effect of aperture size (observing beam) Seyfert nucleus Identified as “pure Seyferts” e.g. NGC 1068, 1097, 4501, 5194, 5033, etc. X-ray irradiated dense molecular gas (XDR) Starbursting dense molecular gas (PDR) High angular resolution observations (using ALMA) is essential for the application of this method at distant sources Observing beam

41. Results Validity of our proposed diagnostic: Comparison with PAH results

42. Comparison with other diagnostics Polycyclic aromatic hydrocarbon (PAH) emission feature at 3.3 um Commonly observed in starburst regions, but destroyed due to a strong radiation field from AGN L-band  lower extinction effect e.g, Imanishi & Dudley 2000, ApJ, 545, 701 Sample of comparison: NGC 1068, 3227, 4051, 4388, 4501, 5033, 7469

43. Comparison with 3.3um PAH diagnostic NGC 3227 ： with nuclear starburst NGC 5033 ： without nuclear starburst ⇒ consistent with our HCN/HCO+ & HCN/CO diagnostic Wavelengths [um] F lambda [10 -15 W/m 2 /um] Imanishi 2002, ApJ, 569, 44 (Aperture sizes are similar to NMA obs.)

44. HCN/HCO + vs 3.3 um PAH diagnostics Currently, good agreement (6 of 7) except for NGC 7469 We may need further investigation on the nuclear power source of NGC 7469... NIR photometry (Genzel et al. 1995, ApJ 444, 129) Patchy radio sources at a few pc scales (Lonsdale et al. 2003, ApJ, 592, 804) Comparison in other Seyfert galaxies are also in progress NGC Nuclear starburst ？ HCN/HCO+PAH 1068No 3227Yes 4051YesYes(?) 4388No 4501No 5033No 7469YesNo (5548?)

45. The CND of NGC 1068 (~ 100 pc scale) is a giant X-ray Dominated Region (XDR). Based on SiO, CN, HCO+, HOC+, H 13 CO+ and HCO lines But they are very weak; not to applicable to many galaxies.. Our method based on HCN/HCO+ is easy to observe! Usero et al., 2004, A&A, 419, 897 XDR chemistry in NGC 1068

46. Our survey suggests: HCN/HCO+ intensity ratios (& HCN/CO ratios) will be a new diagnostic of a dominant power source within the observing beam toward dusty active galaxies (“pure” vs “composite” or XDRs vs PDRs) A caution to a use of HCN intensity as a star-forming dense gas tracer in the circumnuclear regions of AGNs Prevalence of compact (< a few 100 pc) SB in Seyferts 4 of 6 Sy1 hosts nuclear SBs, 7 of 13 Seyferts in total This must be powerful even for extremely dusty nuclei, because mm/submm lines are unaffected by dust ext.  Application to LIRGs/ULIRGs (and high-z submm galaxies w/ ALMA) will be very promising Imanishi et al. 2004, AJ, 128, 2037; Garcia-Burillo et al. 2006, in press

47. Results Application to High-z galaxies & ALMA

48. To go to high-z dusty galaxies XDR/PDR diagnostic using HCN/HCO+ line ratios seems to be very useful among nearby AGNs  application to dusty, high-z galaxies is promising  Then we need observations of high-J HCN/HCO+ lines... ALMA band 3 ALMA band 1

49. A tacama S ubmillimeter T elescope E xperiment: Project director: K. Kohno (U. Tokyo) Project manager: H. Ezawa (NAOJ) Project scientist: S. Yamamoto (U. Tokyo) under a collaboration w/ L. Bronfman (U. Chile) http://www.das.uchile.cl/astechile/ASTEinicio.html http://www.nro.nao.ac.jp/~aste/prop06/

50. NGC 7310 (Sy2) CO(3-2) survey prior to HCN(4-3)/HCO+(4-3) survey CO(3-2) Tpeak ~ 0.36 K in Tmb ASTE beam 22 arcsec Kohno et al. In prep.

51. Tmb ~ 0.5 K !  future search of HCN(4-3) and HCO+(4-3) is planned Rather extended ASTE beam 22 arcsec Kohno et al. in prep. + Wong et al. ATCA CO(3-2) in NGC 1672 w/ ASTE

52. Tmb ~ 0. 9 K !  future search of HCN(4-3) and HCO+(4-3) is planned Very compact ASTE beam 22 arcsec Kohno et al. in prep. + Wong et al. ATCA CO(3-2) in NGC 7552 w/ ASTE

53. Observations of HCN/HCO+ in NGC 7552 ATCA 3 mm observations HCN(1-0) and HCO+(1-0) Three configurations, total 33.5 hrs Calibrator 2326-477, 5.4° away 1921-293 for bandpass, Uranus for flux ATCA 3.5 cm observations from Forbes et al. (1994) reprocessed by M. Dahlem

54. High resol. HCN(1-0) & HCO+(1-0) images HCN on 3.5cmHCO + on 3.5cm Ring-like morphology (r ~ 3”) associated with radio continuum emission (= circumnuclear starburst) Contour = HCN Contour = HCO+ Wong, Ryder, Kohno, & Buta, in prep.

55. HCO+/HCN Line ratio map: almost ~ 1 @SB HCO+/HCN ratio appears remarkably constant, ~1. Ratios of <0.5 seen in Seyferts NGC 1068, 1097 (Kohno et al. 2003). Ratio ~ 1 may be typical of “ starburst ” as opposed to “ AGN ” excitation regime.  Comparison with future HCN(4-3) and HCO+(4-3) observations with ASTE is important to establish a use of high-J HCN/HCO+

56. Summary NMA/RAINBOW 3D imaging survey of CO(1-0), HCN(1-0), and HCO+(1-0) in nearby Seyfert & starburst galaxies HCN/HCO+ (& HCN/CO) ratios could be a new diagnostic tool of power source in dusty active galaxies. Discovery of “HCN enhanced Seyferts”: a signature of XDR Qualitatively OK; further modeling for quantitative comparisons Prevalence of nuclear starburst in Seyfert galaxies 4/6 Sy1 hosts nuclear SBs, 7/13 Sy in total. Application of this method (w/ high-J HCN/HCO+ lines) to dusty galaxies (ULIRGs, high-z submm galaxies, etc.) using ALMA is promising A dense molecular gas survey using Atacama Submillimeter Telescope Experiment (ASTE) and ATCA is in progress

58. “HCN enhanced Seyfert nuclei” Prototype: NGC 1068 I(HCN)/I(CO) intensity ratio up to ～ 0.5-0.6 Never observed in nuclear starbursts Presence of a rotating dense molecular gas disk; perpendicular to a large scale jet Jackson et al. 1993, ApJ, 418, L13 Tacconi et al. 1994, ApJ, 426, L77 Helfert & Blitz 1995, ApJ, 450, 90 Subsequent observations reveal: NGC 5194: Kohno et al. 1996, ApJ, 461, L29 NGC 1097: Kohno et al. 2003, PASJ, 55, L1

59. Enhanced HCN in NGC 5194 (Sy2) I(HCN)/I(CO) are enhanced up to 0.5 cf. Milky Way ~ 0.08 with similar spatial extent CO(1-0) HCN(1-0)