Compact nuclear starburst in the central regions of Sey

fert galaxies

K. Kohno University of Tokyo

“The Central Engine of Active Galactic Nuclei”October 20, 2006 Xi’an, China

OutlineIntroduction:

Roles of dense molecular medium in active galaxies

The surveyCO(1-0), HCN(1-0), and & HCO+(1-0) high resolution imaging survey of Seyfert and starburst galaxies using Nobeyama Millimeter Array & RAINBOW interferometer

ResultsHCN/HCO+ & HCN/CO ratios diagram as a new diagnostics of power source in active galaxies

DiscussionComparison with diagnostics at other wavelengthsApplication to LIRGs/ULIRGsApplication to southern galaxies using ASTE/ATCA

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.

ResultsIntroduction

Roles of Dense molecular gas in the centers of active galaxies

AGN

DenseMolecular Gas

Starburst?

Starburst – AGN connection

Fueling

Obscuration Jet/outflowRadiation (hard)

FuelingSNe/outflow

Radiation (soft)

Obscuring torus consists of dense molecular gas;can be a diagnostictool as well

Stars are formed from dense molecular cores

⇒ AGN – starburst connection

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

Results

Dense gasin Seyfert and starburst galaxies

NMA/RAINBOW 3D imaging survey of dense molecular gas toward local AGN/SBs

20 Seyferts (6 Sy1s and 14 Sy2s) and 12 starburst galaxiesMainly 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)

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 sample15 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

Observed Seyfert galaxies

Sy1s CO HCN HCO+

N1097 ○ ○ ○

N3227 ○ ○ ○

N4051 ○ ○ ○

N5033 ○ ○ ○

N5548 ▽ ▽ ▽

N7469 ○ ○ ○

Sy2s CO HCN HCO+

N1068 (○) ○ ○

N1667 ○

N3079 ○ ○ ○

N3982 ○ × ×

N4258 ○ ○ ○

N4388 ○ ○ ○

N4501 ○ ○ ○

N4579 ○

N5135 ○

N5194 ○ ○ ○

N6764 ○ ○ ○

N6951 ○ ○ ○

N7465 ○ × ×

N7479 ○ ○ ○

○： completed ▽： in progress× ： non detection

19 CO images15 HCN & HCO+ images

Nobeyama CO(1-0) Atlas: type-1 Seyferts

1 kpcNGC 7469

NGC 1097: Kohno et al. 2003, PASJ, 55, L1NGC 5033: Kohno et al. 2003, PASJ, 55, 103NGC 7469: Okiura et al. 2007, in prep.Other galaxies: Kohno et al. 2007, in prep.

Nobeyama CO(1-0) atlas: type-2 Seyferts

1 kpcNGC 3079: Koda et al. 2002, ApJ, 573, 105NGC 4501: Onodera et al. 2004, PASJ, 56, 439NGC 6951: Kohno et al. 1999, ApJ, 511, 157Other galaxies: Kohno et al. 2007, in prep.

NGC 4501

Observed Starburst galaxies

nearby galaxies(D < 20 Mpc) nuclear starburst and evolved starburst galaxiesAlso many of them are in the Ho et al.’s catalogue

Non-Sys CO HCN HCO+

Maffei2 O O O

IC 342 O O O

N253 O O *

M82 O O O

N3504 O O *

N3627 O O O

N3628 O O O

N4527 O O O

N4736 O O

M83 O O O

N5195 O O O

N6946 O O O

O : completed *： in progress

CO, HCN, HCO+Images of Seyferts

NGC 1097

Nucleus ： RHCN/CO = 0.39

RHCN/HCO+ = 1.9

significant enhancement of HCN, any other causes other than high gas density ?

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)

NGC 5194

Sakamoto et al. 1999

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

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.

4.3±0.63 Jy/b km/s 2.3±0.63 Jy/b km/s31±2 Jy/b km/sFlux atthe nucleus:

New results: enhanced HCN in NGC 4501

1kpc

CO(1-0)HCN(1-0)this work

CO: Onodera et al. 2004,PASJ, 56, 439

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

NGC 4388 ： possibly the 6th example

“HCN enhanced Seyfert nuclei”: currently 6 galaxies are identifiedHigh 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)

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 ?

NGC 3227: no HCN enhancement

RHCN/CO = 0.043

RHCN/HCO+ = 0.79Nuclear HCN source is very compact (~ a few 10 pc scale; Schinnerer et al. 20

00, ApJ, 533, 826)

NGC 3079

Nucleus ： RHCN/CO = 0.11

RHCN/HCO+ = 1.3

Within typical values for starburst regions

Rather extended HCO+ ?

RHCN/CO = 0.14; RHCN/HCO+ = 0.63

Radio bubble (Hota & Saikia 2006)

NGC6764: no enhancement

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?

NGC 7479

No HCN enhancement.

NGC 3982

Non-detection

RHCN/CO < 0.33

NGC 7465

Non-detection

RHCN/CO

< 0.18

HCN & HCO+ Images of Starburst Galaxies

200 pc

NGC 6946

IC342

NGC 3628

NGC 3627Maffei2

HCN

HCO+

HCO+HCN

HCN HCO+

ResultsSummary of results:

Line ratios

Seyfert vs Starburst: histogram of RHCN/CO

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

Num

ber

Starburst Seyfert

Seyfert vs Starburst: histogram of RHCN/HCO+

RHCN/HCO+ RHCN/HCO+

Num

ber

Starburst Seyfert

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

HCN/HCO+ & HCN/CO ratios:Seyfert galaxies vs starburst galaxies

Seyfert

Starburst

RHCN/CO

RH

CN

/HC

O+

Difference on dominant power sources within observing aperture beam

Seyfert

Starburst

RHCN/CO

RH

CN

/HC

O+

“Pure AGN”: X-ray irradiated dense molecular gas, i.e., XDRs

“Composite”: AGNwith a nuclear starburst

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

“pure” vs “composite” SeyfertsSeyfert nucleus

X-ray irradiated densemolecular gas (XDR)

Starbursting densemolecular gas (PDR)

“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 densemolecular gas (XDR)

Starbursting densemolecular gas (PDR)

Observing beam

“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 densemolecular gas (XDR)

Starbursting densemolecular gas (PDR)

High angular resolution observations (using ALMA) is essential for the application of this method at distant sources

Observing beam

Results

Validity of ourproposed diagnostic:Comparison withPAH results

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 AGNL-band lower extinction effect

e.g, Imanishi & Dudley 2000, ApJ, 545, 701

Sample of comparison: NGC 1068, 3227, 4051, 4388, 4501, 5033, 7469

Comparison with 3.3um PAH diagnostic

NGC 3227 ： with nuclear starburstNGC 5033 ： without nuclear starburst

⇒ consistent with our HCN/HCO+ & HCN/CO diagnostic

Wavelengths [um] Wavelengths [um]

Fla

mbd

a [1

0-15 W

/m2 /

um]

Imanishi 2002, ApJ, 569, 44(Aperture sizes are similar to NMA obs.)

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

NGCNuclear starburst ？

HCN/HCO+ PAH

1068 No No

3227 Yes Yes

4051 Yes Yes(?)

4388 No No

4501 No No

5033 No No

7469 Yes No

(5548?)

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

XDR chemistry in NGC 1068

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 Seyferts4 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

ResultsApplication toHigh-z galaxies& ALMA

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

Atacama

Submillimeter

Telescope

Experiment:

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.htmlhttp://www.nro.nao.ac.jp/~aste/prop06/

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 beam22 arcsec

Kohno et al.In prep.

Tmb ~ 0.5 K !

future search of HCN(4-3) and HCO+(4-3) is planned

Rather extended

ASTE beam22 arcsec

Kohno et al. in prep.+ Wong et al. ATCA

CO(3-2) in NGC 1672 w/ ASTE

Tmb ~ 0. 9 K !

future search of HCN(4-3) and HCO+(4-3) is planned

Very compact

ASTE beam22 arcsec

Kohno et al. in prep.+ Wong et al. ATCA

CO(3-2) in NGC 7552 w/ ASTE

Observations of HCN/HCO+ in NGC 7552

ATCA 3 mm observationsHCN(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

High resol. HCN(1-0) & HCO+(1-0) images

HCN on 3.5cm HCO+ 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.Wong, Ryder, Kohno, & Buta, in prep.

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+

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 galaxies4/6 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

“HCN enhanced Seyfert nuclei”

Prototype: NGC 1068I(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 jetJackson 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

Enhanced HCN in NGC 5194 (Sy2)

I(HCN)/I(CO) are enhanced up to 0.5cf. Milky Way ~ 0.08 with similar spatial extent

CO(1-0)

HCN(1-0)