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Compact nuclear starburst in the central regions of Seyfert galaxies

“The Central Engine of Active Galactic Nuclei” October 20, 2006 Xi’an, China. Compact nuclear starburst in the central regions of Seyfert galaxies. K. Kohno University of Tokyo. Outline. Introduction: Roles of dense molecular medium in active galaxies The survey

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Compact nuclear starburst in the central regions of Seyfert galaxies

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

  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. Introduction Results

  5. Roles of Dense molecular gas in the centers of active galaxies Starburst – AGN connection AGN Starburst ? Fueling Fueling Jet/outflow SNe/outflow Obscuration Radiation (hard) Radiation (soft) Obscuring torus consists of dense molecular gas; can be a diagnostic tool as well Dense Molecular Gas 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 gJ  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. Dense gas in Seyfert and starburst galaxies Results

  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 ○：completed ▽：in progress ×：non detection 19 CO images 15 HCN & HCO+ images

  11. Nobeyama CO(1-0) Atlas: type-1 Seyferts NGC 7469 1 kpc 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 NGC 4501 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. 1 kpc

  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 O : completed *：in progress

  14. CO, HCN, HCO+ Images of Seyferts

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

  16. NGC 5194 • Nucleus： RHCN/CO = 0.56 RHCN/HCO+ = 2.5 • Similar critical density (nH2>104 H2/cm-3) • Similar optical depth (tau>>1) ⇒ difference of abundance (filling factor) Sakamoto et al. 1999

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

  18. The 4th HCN enhanced Seyfert: NGC 5033 • HCN and HCO+: central concentration, contrary to CO RHCN/CO = 0.23, RHCN/HCO+ = 1.9  This is the 4th “NGC 1068”, i.e., HCN enhanced Seyfert nuclei. Flux at the nucleus: 31±2 Jy/b km/s 4.3±0.63 Jy/b km/s 2.3±0.63 Jy/b km/s

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

  20. NGC 4501: the 5th HCN-enhanced Sy • “the 5th 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 6th 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 • RHCN/CO = 0.043 • RHCN/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： RHCN/CO = 0.11 RHCN/HCO+ = 1.3 Within typical values for starburst regions • Rather extended HCO+ ?

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

  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 RHCN/CO < 0.33

  30. NGC 7465 • Non-detection RHCN/CO < 0.18

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

  32. Summary of results: Line ratios Results

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

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

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

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

  37. HCN/HCO+ abundance: PDR vs XDR 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

  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 X-ray irradiated dense molecular gas (XDR) Starbursting dense molecular gas (PDR) Observing beam Identified as 「composite Seyferts」 e.g. NGC 3079, 3227, 4051, 6764 etc

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

  41. Validity of our proposed diagnostic: Comparison with PAH results 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 Flambda [10-15 W/m2/um] Wavelengths [um] Wavelengths [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 (5548?)

  45. XDR chemistry in NGC 1068 • The CND of NGC 1068 (~ 100 pc scale) is a giant X-ray Dominated Region (XDR). • Based on SiO, CN,HCO+,HOC+,H13CO+ 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

  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. Application to High-z galaxies & ALMA Results

  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. AtacamaSubmillimeterTelescopeExperiment: 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.

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