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