Transcript Slide 1

Phisical properties of dense molecular
gas in centres of Seyfert galaxies
Eleonora Sani
Co-Is: Davies, Sternberg, Gracia-Carpio, Hicks, Tacconi,
Genzel, Engel, Vollmer, Schinnerer, Garcia-Burrillo
Usero, Orban de Xivry
AGN10-dall’orizzonte degli eventi all’orizzonte cosmologico
Roma 11/09/2012
Outline
Introduction
Torus structure
AGN-SF connection
Stellar and molecular gas kinematics
Motivation:
Trace the dense molecular gas
The origin of huge velocity dispersion
Results:
-- PdBI data cubes and observables
-- DYSMAL
-- Can the torus form stars?
E. Sani
AGN10
Roma 11/09/2012
Torus structure
Dust distribution:
• Smooth (continuous)
• Clumpy (discrete)
Pier & Krolik 1992; Granato & Danese 1994
Efstathiou & Rowan-Robinson 1995;
Shartmann+05; Fritz+06
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Nenkova+02, +08; Honig+06;
Schartmann+08
Stellar radiation pressure (Thompson+05; Ballantyne 2008)
Supernovae explosions (Wada & Norman 2002)
Stellar winds (Nayakshin & Cuadra 2007)
External gas accretion (Vollmer+08)
Nuclear star formation can play an important role
E. Sani
AGN10
Roma 11/09/2012
AGN-SF connection
SF happens in all types of AGN
(Schweitzer+06, Veilleux+09)
even in the nuclear region (R < 200 pc)
(Cid Fernandes +04)
SF enhanced for
MBH < 107 M
L/Ledd > 0.5
BH growth and SF happens
simultaneously
E. Sani
Sani+10
AGN10
Roma 11/09/2012
AGN-SF with high spatial resolution
Davies+07
Recent (~40 Myr ago) but no
longer starburst in the
inner 100 pc (with spatial
resolution ~10 pc)
H2 flux
Hicks+09
velocity v. dispersion
E. Sani
AGN10
H2 1-0(S1) traces warm
molecular gas
•at centres v/σ < 1 with
σgas~50-100 km/s
•distribution
must
be
vertically extended with
gas & stars spatially mixed
•random
bulk
motions
must account for σgas in
AGN
Roma 11/09/2012
Molecular gas tracers
• 1-0S(1) H2 traces hot component of the gas (~1000 K) at the edges of clouds
• 1-0S(1) H2 accounts for 10-6-10-5 of the total gas mass
it is not straightforward to derive the vertical extent of the torus
and the origin of the huge σgas
Sani+12
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•
•
HCN(1-0), HCO+(1-0) probe cold (~10100 K) and dense (n >3x104 cm-3)
molecular gas (i.e. ~100-500 times the
density
traced
by
CO
rotational
transitions)
Close to the AGN HCN, HCO+ are
stronger than CO
Chemistry modified by the AGN radion
has little impact on the gas kinematcs
<1” resolution with PdBI
E. Sani
AGN10
Roma 11/09/2012
Kinematics of the dense gas
~1” resolution from PdBI – NGC 3227, 2273, 4051, 6951
(now also NGC 3079, 5033, 6764)
Directly observable constraints:
•major & minor axis size
•Integrated line width FWHM~70-210 km/s
•Separation + PA of the red/blue channels
Sani+12
Modelling the kinematics
Use DYSMAL (Cresci +09, Davies +11)
-Gaussian distribution for the luminosity and mass profiles
-Fixed parameters: ϑ and PA
--Elliptical beam (beam smearing is a key aspect of dynamical modeling)
--Free parameters: R, H, MR
-Thin disk
--Line width is only ~2/3 of that observed
-Thick disk
--Can reproduce all observed characteristics
--Intrinsic dispersion is 25-50 km/s for HCN and HCO+
(about ~50% of H2 1-0S(1) reported by Hicks+09)
--Dispersion is due to a combination of beam smearing of velocity
gradients as well as V/σ~R/H~3-4
Q = √3 H
1
-Toomre Q parameter:
R (1+3*H2/R2) fgas
-Q/Qc>1 always, i.e. dense gas is turbulent with NO ongoing SF
SF within the Torus?
SF within
NGC 6951
PdBI
450 pc
305 pc
180 pc
370 pc
NGC 2273 K-band
LBT Pisces+Flao
• NGC 3227: nuclear (<30 pc) SF is no more occurring (Davies +06)
• NGC 2273, NGC 3227, NGC 6951 show a circumnuclear stellar ring (Martini +03,
Davies +06, Krips +07) with a decreasing stellar dispersion comp. to the nucleus
(Barbosa +06)
• NGC 4051: PAH3.3 not detected within the central 50 pc (Rodrguez-Ardila & Viegas
2003)
SF located in a circumnuclear ring
The model: starburst & torus evolution
Phase I: short, massive
gas infall generates
a massive turbulent disk
(Q~Qc) where SF occurs.
Phase III: the mass acc. rate
decrease significantly.
The collisional disk become
thin and transparent.
Thick disk
Q > Qc
Vollmer, Beckert, & Davies 08
Phase II: SN explosions clear
the intracloud medium leaving
a massive, geometrically thick
collisional disk of dense gas clouds
Conclusion & Future Work
 We observed 4 Seyfert galaxies with the PdBI tracing HCN and
HCO+ molecular lines. The line emission is (marginally)
resolved.
 We measured morphological (dimension & position angle) and
kinematical (channel separation & integrated line width)
parameters. The most remarkable feature is the line width
FWHM ~ 70-210 km/s
 Observed parameters are well reproduced by a thick (R/H = V/σ)
taking into account the beam smearing.
 Increase the statistics: now available data for 3 more sources.
 Add other AGN types to trace the torus structure in different
environments and its evolution.
 Use tracers at 1.3mm, e.g. HCN(3-2), to constrain the chemistry