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NUclei of GAlaxies (NUGA) The IRAM survey of low-L AGN

NUclei of GAlaxies (NUGA) The IRAM survey of low-L AGN. Santiago GARCIA BURILLO Observatorio Astronómico Nacional (OAN)-Spain. The NUGA team S 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).

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NUclei of GAlaxies (NUGA) The IRAM survey of low-L AGN

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  1. NUclei of GAlaxies (NUGA)The IRAM survey of low-L AGN Santiago GARCIA BURILLO Observatorio Astronómico Nacional (OAN)-Spain The NUGA team S 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). (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

  2. FUELING AGN in SEYFERTS and LINERS Where do we stand...? AGN fuelled with material originally away from gravitational field of BH: the problem of angular momentum removal.  Gravitational torques from large-scale (1 kpc) non-axisymmetric perturbations: density waves (m=2, m=1)+ interactions. 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!... Open questions....  Is the ‘inner playground’ (r<1 kpc) of low-L AGN different from ‘pure’ starburst or non-active galaxies?  Are all `secondary instabilities’ equally efficient feeding AGN?  Testing Unified Theories: differences between activity types (1 vs 2), gas tori sizes...

  3. NUclei of GAlaxies: the NUGA project NUGA: a Plateau de Bure CO survey of low-L AGN  CO: best tracer of distribution and kinematics of molecular gas in nuclei.  High spatial resolution (<1”) paramount to reach ‘critical’ scales: <50-100pc. NUGA: first interferometric CO survey of a significant sample of AGN.NUGA sample:12 spirals ranging from Seyferts 1-2 to Liners. Previous surveys done with single-dishes or restricted to a few AGN. Other interferometric surveys not focused on AGN (BIMA-SONG: Helfer et al 2003; OVRO-NRO: Sakamoto et al 1999, Baker et al 2003). NUGA: information from other wavelengths  NUGA has a multi-wavelength approach : HST and ground-based optical/NIR images probe stellar potentials and SF patterns to test the SB-AGN connection. Parallel VLA HI and VLBI radio surveys. NUGA diagnostic tools: • NUGA maps provide gas velocity fields and velocity dispersions. Advantage with respect to ‘only-HST’ surveys!. Derivation of stellar gravitational torques on the gas: sudying the efficiency of AGN feedingNumerical simulations of the gas dynamics based on stellar potentials compared with observations. Evolution of instabilities.

  4. NUGA status NUGA: the sample Full synthesis ABCD maps to be obtained for the bulk of the sample: PdBI high-sensitivity provide high-dynamic range images.Twofold exploitation of NUGA data: ----1/Detailed case-by-case studies:NGC4826 (García-Burillo et al 2003, A&A,407), NGC7217(Combes et al 2003, A&A, in press), NGC1961 (Baker et al 2003 in prep), NGC3718(Krips et al 2003) ----2/Global exploitation of sample upon completion (early 2004?)

  5. First images of NUGA LINER LINER/H SEYF. 1 SEYF. 1 LINER SEYF. 2 LINER SEYF. 2

  6. First images of NUGA -Large variety of circumnuclear disk morphologies:m=2 instabilities (spiral arms, bars), axisymmetric rings, and m=1 instabilities.

  7. NUGA reveals m=1 instabilities • 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 tenstoseveral hundreds of pc. LINER LINER Seyf. 1 NGC4826 NGC1961 NGC4579  150pc AGN AGN AGN   500pc  20pc  0’’.7 (=180pc) CO(2-1) map of NGC1961 shows strong one arm spiral response 0’’.6 (=12pc) CO(2-1) map of NGC4826 shows molecular gas distribution strongly lopsided near AGN. 0’’.6 (=48pc) CO(2-1) map of NGC4579 shows m=1 instability in distribution+kinematics 

  8. m=1 instabilities in NGC4826 (Garcia-Burillo et al 2003, A&A, 407) NGC4826 LINER 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!. 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. Isovelocity maps in N4826

  9. m=1 instabilities in NGC4826 (Garcia-Burillo et al 2003, A&A, 407) Gravitational torques Calculation of stellar gravitational torques on the gas: Can these contribute to AGN feeding? • NIR HST image--->M/L ratio fit on rotation curve-->Fourier decomposition... Gravitational torqueschange of sign for Arm I and Arm II: agreement with CO-based diagnostics. Efficiency of torques is very low: at R=200 pc, angular momentum transfer significant on scales of 1Gyr!  AGN feeding seems negligible for r<50pc!--->new 0.6’’ observations will help to reassess feeding issue.

  10. m=1 instabilities in NGC4826 (Garcia-Burillo et al 2003, A&A, 407) Gas self-gravity  Stellar perturbations seem inefficient to drive angular momentum transfer.  While stellar potential inefficient, is gas self-gravity potentially important? Q maps in NGC4826: •  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 •  Previous claims from HST analysis of colour maps in AGNs: Q=10-100! • Gas self-gravity of observed instabilities might favour/inhibit AGN feeding? • --->to be explored in numerical simulations

  11. Rings and spirals in NGC7217 (Combes et al 2003, A&A, in press) NGC7217 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! 12CO(1-0) (top) and 12CO(2-1) (bottom) maps overlaid with HST V-I image 

  12. Rings and spirals in NGC7217 (Combes et al 2003, A&A, in press) 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

  13. Caught in the act: evidence for asymmetrical feeding? NGC6951 Schinnerer et al 2003 in prep NGC4579 García-Burillo et al 2003b in prep   

  14. Summary and conclusions Wide range of morphologiesNo clear EVOLUTIONARY SEQUENCE emerges thus far. WHY?AGN sate is episodic + The problem of time-scales. Importance of m=1 instabilities: one-arm spirals, lopsided disks ...In some cases, they do not help fuelling AGN however  Most of m=1+m=2 perturbations described are roughly self-gravitating structures (low Q). --More observations are needed: -completion of the NUGA supersample

  15. The NUGA supersample  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.

  16. NGC4826: streaming motions and m=1 perturbations • Diagnostic of streaming motions for m=1 perturbations easiest along minor axis. • 1/Inner arm (I) would be a fast trailing mode (developing outside corotation). • 2/Outer arm (II) would be a slow trailing mode (developing inside corotation). 3/The lopsided m=1 mode of the circumnuclear disk would be a fast trailing mode. • Diagnostic of streaming motions indicate that there might be 2 distinct velocity patterns if (big IF!) the m=1 perturbations are real modes : • Inner modes being fast, cannot help in fueling AGN. • Outer modes being slow, can help however. • Position-velocity strips along minor axis in the 1-0 line (top) and 2-1 (bottom) • The expected pattern of velocity perturbations due to m=1 spirals (slow/fast) according to DW linear models

  17. NGC4826: gas velocities • Both m=1 spirals (arms I/II) are revealed by noncircular motions. • Noncircular motions are also associated with the nuclear lopsided disk. • We have compared the observed deviations with the expected velocity residuals for stationary and fast m=1 modes, either trailing or leading with respect to the gas flow. Velocity patterns of stationary/fast m=1 modes, trailing/leading with respect to the gas flow. Isovelocity maps in N4826

  18. NUclei of GAlaxies:N4826-paper I • CURRENT STATUS: submitted 07-feb-03 • First complete draft by December 02 written by SGB (except for section 4 mostly due to LKH). • Comments received from December 02+January 03. • New version takes into account a fair amount of your comments. • -----1/A new subsection 6.1 dealing with gravitational torques (FC). • -----2/New organisational scheme: sections split into a larger number of subsections (ES). • -----3/Many other items (FC,LKH,AB,ES,SL,RN,FB,PE). • Forthcoming work on ngc4826 • I/ Future A-configuration data next month (?) reaching <0.5’’(=10pc) • II/ Future numerical simulations. Probably I+II/= a second paper this year

  19. NGC4826 • Black Eye=Evil Eye galaxy=Inner disk shows strongly disturbed dusty morphology. A dust lane arc goes across the northern side (r=10”-20”) • (R)SA(rs)ab hosting two counterrotating gaseous disks, where the inner gas disk (both neutral and ionised at r<30’’ =1 kpc) corotates with the stars. The outer gas disk (HI) from 80’’ to 9.8’ counterrotates with the stars. • Transition region (30’’--100’’) identified by kinematical disturbance in Halpha: radial inflow • Activity=LINER nucleus (starburst dominated?).

  20. Molecular gas distribution in NGC4826 • The total molecular gas mass in the primary beam Mgas= 2.3x108 M . • Little is left outside the 1-0 primary beam.....Confirmed by comparison with single-dish+OVRO+BIMA maps • We confirm that there is no two stream flow in the inner disk: CO/HI/Halpha corotate with the stars (r<30’’)

  21. NGC4826: where is the AGN? • Determination of dynamical center • Maximum line widths (second order moments) + maximum symmetry on C(-3.3, -0.8). • Non-thermal source (6cm) on C • X-ray Chandra source on C • Blue (B-I) point-like source on C VLA image of NGC4826 showing non-thermal emission (6cm). Cross= position of dynamical center, based on ‘CO diagnostics’

  22. Molecular gas distribution in NGC4826 • 12CO(1-0) map (2.9”x2.4”) shows molecular gas concentrates in a lopsided circumnuclear disk (CND) with Mgas= 3.4x107 M and r=2’’-3’’(40-50pc), and two one arm spirals=Arm I and II developing at different radii out to r=(35’’) 700 pc. CND • High-resolution(1.1”x0.8”) 12CO(2-1) observations fully resolve the inner disk revealing a lopsided instability (m=1 perturbation). • The central source does not peak at the dynamical center. The lopsided instability stretches out from a radius of 50pc to 100pc) • Previous HCN observations of the nucleus (Helfer and Blitz 1997, ApJ 478) showed a strong lopsided morphology. • Higher-resolution observations (A configuration) are foreseen to reach <0.5’’=10pc!. 12CO(2-1)

  23. Peak brightness maps in the 1-0 line (top) and 2-1 (bottom) with the same asymmetries revealed NGC4826: m=1 perturbations: Arm I and Arm II • Log (radius) -Azimuth plots for the 1-0 (top) and 2-1 (bottom) maps allow to identify the different m=1 perturbations: • I/ The m=1 inner spiral: Arm I is detected in the S side and in 2-1 and 1-0. Arm I is trailing (N side is closer). • II/ The m=1 outer spiral: Arm II mostly detected in 1-0, though beginning present in 2-1. Arm II is first trailing (II a) but ‘changes’ to leading (II b) orientation outward! • Is there any ‘radial’ overlapping between I / II? • What are the implications of II_ _b/II_a?---transition region?

  24. NGC4826 :Distribution of star formation • Asymmetrical patterns in the disk are followed with similar spatial scales by star formation tracers (see Pa map): • m=1 arms: Arm I and Arm II. • North-South asymmetry at odds with any expectation from extinction. • Inner disk in Paschen_alpha is lopsided with strong maximum 20 pc northward from AGN. • Asymmetries in star formation patterns are real and not mere artifacts due to extinction! We overlay the 2cm emission contours (mostly thermal) with the Paschen_alpha image obtained from HST We overlay the 1-0 (top) / 2-1 (bottom) Bure maps with the Paschen_alpha image obtained from HST

  25. NGC4826:Star formation and Compact Star Clusters (CSCs) • Extinction in the Evil Eye • The strongest absorption (red color) on the North side of the disk does not correlate strongly with CO arm:...linked with HI gas instead??. • CO based-Av map weakly correlated with (B-I)-based Av map . • Star formation and CSCs • SFR=0.14 Msun/yr implies vigorous SF in the inner disk fed by molecular gas. • Trend along minor axis for hardness of ionising ratio, with softening towards a ridge at r=17’’ (where CO disk ends): ridge of CSCs. • SF disk is truncated at r=17’’, beyond a ridge of old (>10Myrs) CSC. • We overlay the 1-0 (top) / 2-1 (bottom) Bure maps with the B-I color image obtained from HST data.

  26. NGC4826: HST-Nicmos images: the inner stellar disk • HST-NICMOS map (F160W filter) (color scale) in the inner disk of NGC4826. • We overlay the 1-0 (top) / 2-1 (bottom) Bure maps (in contours) with the USM image obtained from HST-NICMOS data (F160W filter) (color scale).

  27. The origin of m=1 perturbations in NGC4826 • Origin of m=1 perturbations in N4826: • The kinematics (streaming motions) are ‘compatible’ with the velocity patterns expected for: • 1---Fast m=1 modes in the inner disk (50-500pc) This is contrast to m=1 modes driven to counterrotation where pattern speeds very low. • 2---Slow m=1 modes in the outer disk (500pc-1.5kpc) • No two-stream flow in inner disk: unless detection of counterrotating stellar disk elusive • Numerical simulations will test the viability of other mechanisms favouring m=1 instabilities (see Shu et al 90; Junqueira and Combes, 1996). • Disks with high gas content DO favour the onset of fast m=1 modes close to the nucleus. • Several lines evidence for a past gas accretion episode: • 1/Counter-rotating outer disk • 2/Infall motions (R=30’’-100’’) • 3/Molecular gas+SF disk truncated (R<35’’) • 4/’Cold’ stellar disky component (R<30’’)

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