How to Feed AGN

The NUGA survey view

Santiago GARCIA-BURILLO

Observatorio Astronómico Nacional (OAN)-Spain

The NUGA teamS García-Burillo(1), F.Combes(2), A.Eckart(3), L.Tacconi(4), L.Hunt(5), S.Leon(6), A.Baker(4), P.Englmaier(7), F.Boone(8), E.Schinnerer(9), R.Neri(10), M.Krips(3).

(1)-OAN, Spain (2)-LERMA, France (3)-Universitaet zu Koeln, Germany (4)-MPE, Germany

(5)-CAISMI, Italy (6)-IAA, Spain (7)-Universitaet Basel, Switzerland (8)-Bochum University,Germany (9)-NRAO, USA , (10)-IRAM, France

The Evolution of Starbursts, August 16-20, 2004, Bad Honef, Germany

FUELING AGN in SEYFERTS and LINERS

->AGN fuelled with material originally away from gravitational field of BH: problem of angular momentum removal.

-> Weak correlation between 1kpc-scale perturbations and activity in ‘Local Universe’ AGN: Seyferts and LINERs.

-> Critical scale for AGN feeding: <100pc. AGN duty cycle is short!

-> Search for correlation with `secondary instabilities’ from 1 kpc to <100 pc:

nuclear bars? spiral gas waves?, nuclear-warps? m=1 modes? ... No consensus on the driving mechanism!...(only one? several? ‘none’?...)

-> Is the ‘inner playground’ (r<1 kpc) of low-L AGN different from non-active galaxies?

Where do we stand...?

( Combes 2000-2004; Wada et al 2000-2004; Englmaier & Shlosman 2000; Shlosman 2001; Maciejewski et al 2002, 2004; Knapen 2001, 2004; Jogee 2004; Laine et al 2002; Garcia-Burillo et al 2000, Schinnerer et al 2000.......and many others!)

-> CO: best tracer of distribution and kinematics of molecular gas in nuclei.

-> High spatial resolution (0.5’’-1”) paramount to reach ‘critical’ scales: <50-100pc.

-> NUGA: first interferometric CO survey of a significant sample of AGN.

->NUGA core sample: 12 spirals ranging from Seyferts 1-2 to Liners. NUGA aims at compiling

sample of 25-30 galaxies by including PdBI data available from consortium members.

NUclei of GAlaxies: the NUGA project

NUGA: a CO survey of low-L AGN with IRAM Bure Interferometer

->Multiwavelength approach:beyond CO maps-->NIR HST , VLA HI and VLBI radio images.

->Derivation of gravitational torques on the gas: efficiency of AGN feeding.

->Numerical simulations of the gas dynamics compared with observations. Evolution of instabilities.

Strategy for NUGA :

-> Twofold exploitation of NUGA data:

----1/Detailed case-by-case studies: NGC4826 (García-Burillo et al 2003, A&A,407), NGC7217(Combes et al 2004, A&A, 414), NGC1961 (Baker et al 2004 in prep), NGC3718(Krips et al 2004) ----2/Global exploitation of sample upon completion (06/04)

CO images of NUGA

T/LINER

LINER/SEYF. 1

LINER

HII/T

SEYF. 1

SEYF. 2

SEYF. 2

LINER T/LINER

SEYF. 2

SEYF. 2

T/SEYF. 2

•The new 0.5’’-0.7’’ maps reveal m=1 perturbations appearing as one-arm spirals and lopsided disks in several galaxies. Perturbations appear at various scales, from several tens to several hundreds of pc.

NGC4826 NGC1961

0’’.6 (=12pc) CO(2-1) map of NGC4826 shows molecular gas distribution lopsided near AGN.

LINERT/LINER

NUGA reveals m=1 instabilities

AGN AGN

0’’.7 (=180pc) CO(2-1) map of NGC1961 shows strong one arm spiral response

(Garcia-Burillo et al 2003, A&A, 407; and 2004 in prep)

( Baker et al 2004, in prep)

20pc 500pc

I/ TRANSITION objects: NGC4826

CO(2-1)(contours)-on B-I/HST(colours)

(Garcia-Burillo et al 2003, A&A, 407; and 2004 in prep)

->NGC4826 is a transition object hosting 2 counter-rotating gas disks. Molecular gas disk corotates with stars.

-> NUGA maps show two m=1 spirals (Arms I-II; r>100pc) and a lopsided nuclear disk at r<80-100pc

-> Analysis of observed streaming motions suggests inner instabilities are ‘fast’ trailing m=1 perturbations......Inner instabilities would not drive AGN fueling!.

Searching for observational evidences of ‘ongoing’ feeding...

->Kinematical signature of lopsided nuclear disk along minor axis suggestive of outflow rather than inflow near AGN.

CO(2-1) p-v diagram along minor axis

->Large molecular gas concentration at radii ~ 80-100pc from the AGN (0.5x108Msun), but negative evidence of inflow from gas kinematics.

Conclusion....

40pc

II/ LINERS: NGC4579 (Garcia-Burillo et al 2004 in prep)

Searching for observational evidences of ‘ongoing’ feeding...

-> Molecular gas kinematics in the inner 100pc disk (~105Msun )suggestive of expanding motions? highly elliptical/non coplanar orbits?... AGN feeding issue still unclear ! (modelling in progress...)

Conclusion....

-> NGC4579: S 1.9/L1.9 barred spiral. Prototype of low-L AGN.

-> Molecular gas distribution in inner 500pc mimics gas response to bar potential: gas piles up in 2 leading spiral arcs: x1 orbits crowding However m=2 point-symmetry breaks up in the inner 100pc disk: lopsidedness takes over!. AGN in off-centered 150pc gas disk with shell-like features seen in HST V-I and PdBI CO(2-1) maps

CO(2-1) p-v diagram along major axis

CO(2-1)(contours)-on V-I/HST(colours)

Kinematical signature of highly non-circular motions for gas on major axis p-v plot near AGN (<100pc) 70pc

AGN

-> NGC6951: barred spiral prototype of Seyfert 2.-> Molecular gas distribution inside 700pc suggests gas along x2 orbits in bar potential: gas piles up in highly contrasted nuclear spiral arms (~4x108 Msun) feeding starburst while little molecular gas 200 pc from the AGN.

CO(2-1)-un weight on J-H/HST(colour) CO(2-1)-na weight on J-H

-> CO(2-1) central clump on the AGN of ~106Msun betrays feeding in the past.

-> NW gas extension of ~107Msun linked to filamentary dusty spiral in J-H HST map is tantalazing

evidence of ongoing feeding

CO(2-1) Major Axis p-v plots

200pc

Searching for observational evidences of ‘ongoing’ feeding... III/ SEYFERTS: NGC6951 (Schinnerer et al 2004 in prep)

Conclusion....

Evaluation of Gravitational Torques on the Gas

->Gravitational torques of the stellar potential on the gas can be derived if fair

representations of both are available.

-> We use NIR HST images to get the potentials and the high-resolution CO maps from

NUGA to get the gas distribution in our sample.

-> Efficiency of torques will depend on the strength of non-axisymmetric perturbations

but also on the existence of phase shifts between the gas and the stars distributions.

Deriving potentials ...

I

Evaluation of Gravitational Torques on the Gas

II

Deriving torques ...

III

Getting the efficiencies...

Gravitational Torques in NGC4826 (Garcia-Burillo, Combes, Schinnerer et al 2004 in prep)I/ TRANSITION objects

40pc

CO(2-1)(contours)-on H band HST(colours) deprojected Fourier decomposition of stellar potential: Q_i, Phi_i

The stellar potential and gas distribution in the inner 500pc playground...

->Strength of non-axisymmetric stellar potential, measured by QT , is low for 500pc>r>50pc.

->Larger values of QT for r<50pc are due to small oval perturbation

Gravitational Torques in NGC4826 (Garcia-Burillo, Combes, Schinnerer et al 2004 in prep)I/ TRANSITION objects

40pc

Torques Map

Efficiency of Torques

->Torques map reproduces butterfly-like pattern driven by the stellar oval for r<100pc, roughly oriented N/S.

->Efficiency of stellar torques to drive angular momentum loss in gas is low at all radii: low + oscillating values of dL/L. Average value slightly>0! -> This is compatible with scenario inferred from CO observations: while gas concentration is large at r<100pc , dynamical evidence of inflow in this transition object is scarce.--->Stellar perturbations have virtually no role in AGN feeding at present

Gravitational Torques in NGC4579 (Garcia-Burillo, Combes, Schinnerer et al 2004 in prep)II/LINERS

CO(2-1)(contours)-on I band HST(colours) deprojected Fourier decomposition of stellar potential: Q_i, Phi_i

The stellar potential and gas distribution in the inner 500pc playground...

->Stellar potential strength, measured by QT , is driven by the stellar bar identified in the image.

->Large values of QT for r<200pc are measured.

150pc

(Garcia-Burillo, Combes, Schinnerer et al 2004 in prep)

Gravitational Torques in NGC4579 II/LINERS

Torques Map

Efficiency of Torques

->Torques map reproduces butterfly-like pattern driven by the large scale stellar bar. Change of sign and orientation of quadrants fit the theoretical expectations.

->Efficiency of stellar torques is ~5 times larger in NGC4579 than in NGC4826: dL/L<0 over 800pc down to r=200pc.

->Stellar torques become positive for r<200pc , however! !--->Stellar perturbations have virtually no role in AGN feeding at present.

150pc

(Garcia-Burillo, Combes, Schinnerer et al 2004 in prep)

Gravitational Torques in NGC6951 III/SEYFERTS

CO(2-1)(contours)-on H band HST(colours) deprojected Fourier decomposition of stellar potential: Q_i, Phi_i

The stellar potential and gas distribution in the inner 500pc playground...

->Large-scale NIR images of NGC6951 reveal a stellar bar on kpc scales. However, QT is here driven by a nuclear bar/oval identified in the image at r<500pc.

->Low values of QT are measured for the nuclear bar.

200pc

(Garcia-Burillo, Combes, Schinnerer et al 2004 in prep)

Gravitational Torques in NGC6951 III/SEYFERTS

Torques Map

Efficiency of Torques

->Torques map reproduces butterfly-like pattern driven by the nuclear bar.

->Efficiency of stellar torques to get rid of Lgas is ~3-5 times larger in NGC6951 than in NGC4826: dL/L<0 over 800pc down to r=300pc.

->Average stellar torques become very low and marginally positive for r<300pc, however!--->Stellar perturbations have virtually no role in AGN feeding at present.

• NUGA maps unveil a lot of m=1 instabilities in AGN. ----->The role of m=1 modes in fuelling still controversial: see, for example, NGC4826

•NUGA maps show wide range of instabilities at r~10-500 pc from AGN. This includes all types of m=2 and m=1-like perturbations .

Summary

•Analysis of stellar gravity torques on nuclear gas disks of NGC4826(T), NGC4579(LINER) and NGC6951(Seyfert) allowed us to probe the T/LINER/Seyfert sequence and search for a trend in AGN feeding history.---> AGN feeding process may happen in two steps: stellar torques help at feeding nuclear SB ‘first’ on 100pc scales, and a second transitory mechanism is swichted on for ´a while’ in a second step (gaseous?(=viscosity?), stellar?(=short-lived nuclear bar?))

•Perturbations seen in NUGA maps can be either self-gravitating (low Q) or non self-gravitating (high Q).

Caught in the act: a nuclear bar feeding M100 AGN?

POSITIVE TORQUES

POSITIVE TORQUES

NEGATIVE TORQUES

NEGATIVE TORQUES

-> Global exploitation of NUGANUGA aims at compiling sample of 25-30 galaxies by including PdBI data available from consortium members. Availability of non active galaxies crucial to build up comparison sample.

The NUGA supersample

Searching for AGN ‘feedback’ on molecular gas...

CO(1-0) (PdBI;Schinnerer et al. 00)

Molecular Gas Inventory of the CND of NGC1068

•Molecular survey (9 species) provides new constraints to the chemistry of the Circumnuclear Disk (CND) in NGC1068.

•X-ray driven chemistry models explain abundance ratios measured in the CND

NGC1068: Seyfert 2 Usero, García-Burillo, Fuente et al. 2004, A&A, 419

NGC7217

12CO(1-0) (top) and 12CO(2-1) (bottom) maps overlaid with HST V-I image

-> LINER with high degree of axisymmetry. Halo+bulge dominant. It has 3 stellar rings but paradoxically no strong bar!

-> NUGA 1-0 map shows molecular gas in circular ring (m=0) covering nuclear dust ring and multi-arm spiral pattern identified by HST.

-> Little gas near AGN source. Nuclear spot seen in 2-1 and 1-0 of < 106 solar masses. Associated with stochastic mini spiral seen by HST.

-> Inner boundary of molecular ring is very sharp!:...

. Evidence that AGN fueling is negligible inside the ring at present!

Self-Gravitating

Non Self-Gravitating

...and m=2 instabilities

(Combes et al 2004, A&A, 414)

Numerical simulations

-> The N7217 paradox: 3 contrasted rings but no bar at present!

-> N-body simulations including stars+gas self-gravity and star formation explore two extreme models to account for `present’ morphology:

--1/Run A: mild persistent oval.

--2/Run B: strong bar dissolved after gas

infall

-> Mild oval model is favoured. Nuclear gas ring formed near ILR of oval distortion. Gas piles up on the inner side of the ring:...

....no significant AGN feeding at present !

Run A

Run B

LINERS Rings and spirals in NGC7217 (Combes et al 2004, A&A,414 )

-> Transition object hosting 2 counter-rotating gas disks. Molecular gas disk corotates with stars.

-> NUGA maps show two m=1 spirals (Arms I-II; r>100pc) and a lopsided nuclear disk at r<40-50pc

-> Analysis of observed streaming motions suggests inner instabili-ties are ‘fast’ trailing m=1 pertur-bations...

Inner instabilities would not drive AGN fueling!.

Isovelocity maps in N4826

m=1 instabilities in NGC4826 (Garcia-Burillo et al 2003, A&A, 407)

NGC4826

Expected pattern of velocity perturbations due to m=1 spirals (slow/fast) according to DW linear models. For fast ‘modes’ m=1 develops mostly outside corotation.

Transition

-> Stellar perturbations seem inefficient to drive angular momentum transfer.

-> While stellar potential inefficient, is gas self-gravity potentially important?

-> Estimate of Toomre Q parameter for the gas disk:

CO-->Ngas and Qgas:

•1/Arm I-II have very low Q ( close to 1)

•2/Lopsided instability in nuclear disk may have Q<2-3

-> Gas self-gravity of observed instabilities might favour/inhibit AGN feeding?

--->to be explored in numerical simulations

Q maps in NGC4826:

Gas self-gravity

T/LINERS

m=1 instabilities in NGC4826 (Garcia-Burillo et al 2003, A&A, 407)

Seyferts m=1, 2 instabilities in NGC4579 (García-Burillo et al 2004, A&A, in prep )

CO(2-1)-PdBI (contours) on V-I/HST(grey) CO(2-1)-PdBI (contours) on Halpha/HST(colour)NGC4579

-> NGC4579: S1.9/L1.9 barred spiral. Prototype of low-L AGN.

-> Molecular gas distribution in inner 500pc mimics gas response to bar potential: gas piles up in 2 leading spiral arcs: x1 orbits crowding However m=2 point-symmetry breaks up in the inner 100pc disk: lopsidedness takes over!.

AGNAGN

->AGN in off-centered 150pc gas disk with shell-like features seen in HST V-I and PdBI CO(2-1) maps.

->Little molecular gas close to the AGN: closest molecular complex of ~a few105Msun at 80-100pc from BH.

65pc

V-I Ha

Seyferts m=1, 2 instabilities in NGC4579 (García-Burillo et al 2004, A&A, in prep )

-> Any evidence of AGN fuelling?: molecular gas kinematics very complex from 500pc down to 50pc scales.

->’Odd’ gas kinematics on Northern spiral arm (~150-500pc).

CO(2-1) isovelocitiesCO(2-1) Major Axis p-v plot

-> Molecular gas kinematics in the inner 100pc disk suggestive of expanding motions? highly elliptical/non coplanar orbits?...

-> AGN feeding still unclear ! (modelling in progress...)