1 / 37

NUCLEI OF GALAXIES: First results/STATUS

NUCLEI OF GALAXIES: First results/STATUS. Santiago GARCIA BURILLO (burillo@oan.es) Observatorio Astronómico Nacional (OAN). FUELING THE AGNs IN SPIRALS. AGN are fueled from material (gas/stars) away from the gravitational field of the BH.

morfin
Download Presentation

NUCLEI OF GALAXIES: First results/STATUS

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. NUCLEI OF GALAXIES:First results/STATUS Santiago GARCIA BURILLO (burillo@oan.es) Observatorio Astronómico Nacional (OAN)

  2. FUELING THE AGNs IN SPIRALS • AGN are fueled from material(gas/stars) away from the gravitational field of the BH. • For gas infall to occur we need to remove angular momentum. • There is no consensus on the mechanisms driving the infall of gas towards the central BH: do they depend on AGN luminosity/type?: • I/High-luminosity AGNs need large accretion rates (102-3 M/yr) which must involve large-scale gravitational instabilities. These can trigger a nuclear starburst. Mass-loss rate/stellar collisions/disruptions may account for the necessary fuel. • I/Low-luminosity AGNs(Seyferts 1-2 and Liners) :although they need smaller accre-tion rates (10-2 -10-1 M/yr), these probably involve also large-scale gravitational instabilities. • Different types of large-scale gravitational instabilities have been described: • 1/Large-scale stellar bars: gas infall stops at ILR barrier. • 2/Decoupled nuclear stellar bars (bars within bars): may drive gas to smaller scales < 100pc. • 3/Gas waves: either spiral or barred: probably effective at small scales when Mgas/Mtot>0.25. • 4/Micro-warps:driven by pressure effects. • 5/Lopsided/m=1 instabilities: either related to counterrotation or BH-dominated potentials. • Are large-scale instabilities different for Seyf 1, 2, 3? • Are they equally efficient in driving the gas inwards? • Are molecular gas tori in Seyferts extended to 50-100pc?

  3. NUCLEI OF GALAXIES : the NUGA project -No interferometric CO survey of a significant sample of AGNs has even been conducted so far.-Previous surveys: -done with low-resolution single-dish antennas (studying molecular gas on kpc scales). -restricted to very few cases (poor statistics).-NUGA sample=12 nearby AGNs covering the whole sequence of activity types (1, 2, 3=Liners)-High spatial resolution(<1”) will allow study of molecular gas distribution/kinematics on scales <50-100pc.-Multiwavelength approach: HST and ground-based optical/NIR images available to derive stellar potentials/SF patterns, ...-CO observations can be confronted to numerical simulations of gas dynamics based on stellar potentials derivedfrom NIR images.-NUGA aims at enlarging the sample to 25-30 galaxies by adding available data on AGNs observed by consortium members. Non active galaxies are also available (comparison sample)

  4. NUCLEI OF GALAXIES : the NUGA project

  5. NUCLEI OF GALAXIES : the NUGA project DATA REDUCTION for 1st run: August 2001. 4 GALAXIES completed in CD configuration Completed+reduced Completed+reduced NGC 3718 Completed+reduced NGC 4826 Completed+reduced NGC 7217 Completed+reduced NGC 1961 • People involved so far: (4) S.Garcia-Burillo, F.Combes, F.Boone. R.NeriMORE PEOPLE ARE WELCOME TO ACTIVELY PARTICIPATE IN THE FUTURE...

  6. NUCLEI OF GALAXIES : the NUGA project 2nd run of observations still in progress (May 01-Nov 01) (3 GALAXIES) 2 galaxies completed in D configuration so far Deferred for winter 2002: NGC2782 NGC 6951 NGC 3147 Preliminary reduced

  7. NUCLEI OF GALAXIES : the NUGA project 3rd run (Nov 01-May 02): 5 GALAXIES to be observed in different configurations settings: B (NGC1961, NGC4826), 3 Ds (NGC3627, NGC4579, NGC6574) and 3 configurations to choose among B/C (3 Cs? or 2Cs+1 B?)

  8. First results of NUGA project -High-dynamic range images are obtained after a standard synthesis.-The variety of morphologies of circumnuclear gas disks is remarkably large: unresolved compact sources, nuclear spiral arms, rings, lopsided and other asymmetric features.-The survey will provide a unique data set to be exploited ona case-by-case basis, and globally as a homogeneous sampleof nearby AGNs.

  9. (R)SA(r)ab isolated non-barred galaxy hosting three stellar (s) /gaseous (g) rings at radii r=77’’ (s+g), r= 31’’ (s+g) and r=8’’(g)--10’’(s). • Activity: low-luminous AGN classified as Liner. • Origin of 3 rings controversial as bi-symmetric disturbance very weak (see Buta et al 1995, ApJ, 450) • However, a weak stellar oval distortion might drive an ILR at r=8’’-10’’. • Discovery of an inner polar ring of ionised gas inside r=3’’(Sil’chenko and Afanasiev 2000, A&A,364) NGC7217 NUGA first results • 12CO(1-0) (3.2”x2.8”) map shows a molecular gas ring of r=10’’ (0.8kpc) coinciding with the stellar ILR ring. • Mgas=2.2x108 Mwithin the ring, but Mgas<5x106 M inside it (r<160pc): no massive disk accretion near the AGN. • CO ring astonishingly circular with hardly any signature of non-circular motions. 12CO(1-0) 12CO(2-1) • 12CO(2-1) (1.6”x1.4”) map shows the molecular gas ring at ILR is resolved out (also close to primary beam at 230Ghz!). • Tentative detection of a compact disk inside r=3’’ in the 2-1 line! See feature in NIR color images. • The implied 2-1/1-0 ratio (3 sigma) > 1.4: partly optically thin gas.

  10. Is there any molecular gas counterpart for the recently discovered polar ring of ionised gas ? : Not quite, judging from the results of the 1-0 line! NGC7217 12CO(1-0) spectra for the inner region: RA=(+10.5’’ , -9’’), DC=( -5.5’’, +14’’). Scale: 1’’=84pc

  11. However there might be a link between the polar ring of ionised gas and the tentative detection of a compact source detected in the 12CO(2-1) line! • Higher resolution/sentivity observations might be rewarding to settle the question. NGC7217 12CO(2-1) spectra for the central unresolved source (only) tentatively detected: see variations of the profile (to be confirmed!...)

  12. NGC7217 12CO(1-0) integrated intensity levels (contours) overlaid with id. for 12CO(2-1) (color scale) • 12CO(1-0) integrated intensity map shows a broad-ring (200-300pc). Comparsion with color indexes obtained by Buta et al 1995, ApJ, 450, indicates CO ring is significantly broader than the dust lane ring. • Radius of 12CO(1-0) ring (=10’’) similar to stellar ring i.e., significantly larger than dust lane ring (7’’-8’’)!

  13. NGC7217 12CO(1-0) integrated intensity map(color scale) overlaid with isovelocity levels (1-order moment) derived with a 4-sigma clip on the data (contours) • Regular velocity pattern dominated by rotation: no signature of streaming motions.

  14. NGC7217 12CO(1-0) position-velocity plot across the major axis

  15. NGC7217 12CO(1-0) (contours) overlaid with HST- V-I image (color scale=bluer means more heavily absorbed) • 12CO(1-0) map clearly shows molecular gas is related to the dust ring, but also to the filamentary stochastic multi-arm spiral pattern. • Projection effects accounted, spiral is trailing with respect to the gas flow. V-I color image 12co(2-1) 12CO(2-1) central source (contours) coincides with mini-spiral (?) seen in V-I color image.

  16. (R)SA(rs)ab hosting two counterrotating gasesous disks, where the inner gas disk (both neutral and ionised at r<30’’ =1 kpc) corotates with the stars. The outer gas disk (HI) counterrotates with the stars. • Activity=Seyfert 2 nucleus. • Inner disk shows strongly disturbed dusty morphology. A dust lane arc go across the northern side (r=10”-20”) • Previous HCN observations of the nucleus (Helfer and Blitz 1997, ApJ 478) showed a strong lopsided morphology. NGC4826 NUGA first results • 12CO(1-0) map (3.8”x3.6”) shows molecular gas concentrates in a compact central disk with Mgas= 2.2x108 M and r=5’’(180pc), and an asymmetric spiral arm with Mgas= 1.5x108 M . • High-resolution(1.8”x1.7”) 12CO(2-1) observations spatially resolve the inner disk and the spiral structure, revealing the presence of a strong lopsided instability (m=1 mode). • Higher-resolution observations are under way. 12CO(1-0) 12CO(2-1)

  17. NGC4826 • Asymmetrical patterns appear in the CO maps at different levels: • I/ The m=1 outer spiral (detected in 2-1 and 1-0) • II/The off-centered bar-like structure (id) • III/The central source, partly resolved in the 2-1 line, does not peak at the dynamical center, derived from CO (lopsided instability?) Integrated intensity 12CO(2-1) map (contours) overlaid on 12CO(1-0) map (color scale).

  18. NGC4826 • Peak brightness map in the 1-0 line (colour scale) overlaid with the integrated intensity map (contours): same asymmetries are revisited/revealed • Same for the 2-1 line.

  19. NGC4826 • Beware of side lobes when dynamic range of the image is high!More observations (under way) will partly improve deconvolution of the maps, including residual side-lobe contamination R=8’’ R=15’’ 12CO(1-0) (left) and 12CO(2-1) (right) position-velocity plots taken along the kinematical minor axis of NGC4826 showing (most probably) spurious anomalous velocities due to residual side-lobe contamination.

  20. NGC4826 • The outer one-arm spiral is revealed by noncircular motions. • Molecular gas co-rotates with the stars within the Bure primary beam field, contrary to the outer HI disk that counter-rotates with respect to the inner disk. • Do we expect the onset of a counterrotating instability in the inner disk where there is no two-stream flow??: • Results of numerical simulations... 12CO(1-0) position-velocity plot taken along the kinematical major axis of NGC4826 helps to detect the signature of the m=1 spiral arm, by the identification of non-circular motions.

  21. NGC4826 • Asymmetrical patterns in the disk are mimicked by star formation tracers, such as Paschen_alpha (color image below): • m=1 outer arm • off-centered bar-like structure • inner disk (ring?: see Leslie´s talk) • B-I color image based on HST showing heavy absorption on the northern (closer to us) side !

  22. COUNTERROTATING MOLECULAR GAS DISKS IN SPIRALS • Bure12CO(1-0) (4’’x3’’) observations of the nucleus of NGC3593: a spiral hosting two counterrotating stellar disks. • Molecular gas is concentrated in a highly-structured circumnuclear disk (CND), consisting of a ring and a strong one-arm spiral instability (m=1 mode). • Observations allowed us to model the kinematics of molecular gas as a m=1 stationary (i.e. with p  0) spiral, that is leading with respect to the gas flow: are lopsided/one-arm spirals associated with counterrotation in galaxies? Velocity patterns of stationary and fast m=1 modes, either trailing or leading with respect to the gas flow. Integrated intensity (above) and peak brightness (below) 12CO(1-0) maps in NGC3593. Isovelocities overalied on the bottom image display streaming motions connected to the m=1 spiral. García-Burillo et al. 2000, A&A, 363, 869

  23. García-Burillo et al. 2000, A&A, 363, 869 NUMERICAL SIMULATIONS: do they help? To understand the observed gas response we run self-consistent numerical simulations including stars/gas in a physical scenario close to NGC3593. The secular evolution of a counterrotating stellar + gaseous disk similar to NGC3593 reproduces spontaneously a strong m=1 response! . The plot displays the transitory regime (T=500Myrs) STARS GAS • Are counterrotating spirals exotic/infrequent? • How can counterrotating instabilities help in feeding the AGN? • Counterrotating spiral disks as NGC4826 or NGC3593 are not as exotic as they might seem if hierarchical merging senarios are successful in builduing up galaxy disks in the past. • The study of counterrotating instabilities using self-consistent numerical simulations might help to identify potential counterrotator disks (see Combes and García Burillo 2002, in prep)

  24. SAB(rs)c supermassive (M tot 1x1012 M) barred spiral with a distorted optical disk showing strong asymmetries. • Activity: low-luminous AGN classified as Liner. • HI disk with head-tail morphology consisting of a southern one-arm spiral and a northern extension suggesting gas stripping (Shostak et al 1982, A&A, 115) . • Liesenfeld et al 1998, MNRAS, 300 speculated that NGC1961 is an advanced merger, after discovery of a double nucleus in VLA radio continuum maps . NGC1961 NUGA first results • 12CO(1-0) map (3.4”x3.2”) shows molecular gas concentrates in a compact central disk with Mgas= 1x1010 M(!!) and r=4’’(1 kpc), and an asymmetric spiral arm extending southward with Mgas= 0.6x1010 M . • 12CO(2-1) observations resolve partly the inner disk (higher-resolution <1” observations are under way). • The one-arm spiral structure seen in CO maps, suggestive of a strong m=1 mode, has a counterpart in radio-continuum maps. • We found no evidence of double nucleus in our maps. 12CO(1-0) 12CO(2-1)

  25. NGC1961 • 12CO(1-0) map (contours) superposed on mm-continuum source detected at 3mm (color scale): • 3mm continuum emission is off-centered with respect to the dynamical center! • Link with CO northern spur? 12CO(1-0) map (black contours) superposed on mm-continuum source detected at 3mm (white contours) and peak brightness map.

  26. NGC1961 • 12CO(2-1) zero-moment map (color scale) overlaid with 12CO(1-0) data (contours): • Studying the compact CNDrequires higher resolution!. • Spiral arm structure is partly filtered/resolved out at 230Ghz.

  27. 12CO(1-0) position-velocity plot taken along the kinematical major axis of NGC1961 reveals the signature of strong velocity perturbations (100 km/s deviation from circular rotation!!) near the crossing of the one-arm spiral feature. • Suggestive of a m=1 density wave mode. NGC1961 • 12CO(1-0) isovelocity contours, overlaid with integrated intensity map, indicate strong streaming motions linked with the m=1 arm.

  28. NGC1961

  29. SB(s)a interacting barred spiral with a strong warp identified in optical images, linked to interaction with NGC3729. • Activity: AGN classified as Seyfert 1. • HI map shows a close to edge-on orientation of a warped disk (Schwarz 1985, A&A, 142) This warp can succesfully explain the optical appearance. • Eckart et al 2001, in prep detected molecular gas using CO and HCN lines. NGC3718 NUGA first results • 12CO(1-0) map (3.4”x3.2”) shows clumply molecular gas emission, coming mainly from a close-to-the-center clump with Mgas= 2x108 M and size S=7’’(1 kpc). See however shift between the center and the CO clump. • We detect a secondary clump lying along the major axis disk with Mgas= 6x107 M. • 12CO(2-1) observations resolve partly the inner clump. • Continuum source is detected at 3mm and 1mm. 12CO(1-0) 12CO(2-1)

  30. NGC3718 • Is the CO central clump lying in front of the nucleus (in projection), but sitting in in the outer disk? (the latter would imply stringent upper limits on the molecular gas close to AGN source): • SOME CLUES: • 1mm continuum (dust!) is detected in (0,0), although there is a shift with respect to the peak of CO emission:However, part of the molecular gas might be linked to the AGN. • Molecular gas emission from the central clump (detected in both lines of CO) show small line-widths (at most 50 km/s). 12CO(2-1) (contours) overlaid with the 1mm-continuum image (color scale)

  31. NGC3718 • 3mm continuum (n-th/th) is detected in (0,0), but also shifted with respect to CO emission. • In-depth study of CO kinematics and comparison with other gas tracers crucial to disetangle the origin of emission. • 30m observations/related PdB mosaic (Eckart and collaborators) 12CO(1-0) (color scale) overlaid with the 3mm-continuum image (color scale).

  32. NGC3718 Kinematics of molecular gas: Isovelocities derived for 12CO(1-0) suggest the clump may represent gas related to the nucleus. We need to know the outer disk kinematics to compare with... • 12CO(1-0) position-velocity plot (color scale) across the central CO clump (peak position): • We detect an overall gradient of 100 km/s on scales of 8’’-10’’: to be compared with the expected dv/dr near the nucleus of N3718...

  33. NGC3718

  34. NGC3718

  35. NGC3147 • SA(rs)bc non-barred spiral. • Activity: AGN classified as Seyfert 2 (Ptak et al. 1996, ApJ, 459) NUGA first results • 12CO(1-0) /12CO(2-1) maps with only low resolution 5”/ 3” D configuration so far: more observations under way!. • Molecular gas distribution in the nucleus is highly-structured, consisting of: • A compact unresolved source in the dynamical center with Mgas= 2x108 M and radius r<3’’(800 pc). • Two nested spirals, extending up to r=16’’(4.5 kpc) with Mgas= 4x109 M . • 12CO(2-1) observations resolve partly the inner nested spiral. 12CO(1-0) 12CO(2-1)

  36. SAB(rs)bc intermediately barred spiral . • Activity: AGN classified as Seyfert 2. • Previous low-resolution (4”) observations of molecular gas (CO and HCN) with Nobeyama array showed ‘twin peaks’ morphology in the nucleus. NGC6951 NUGA first results • The first (rough) 12CO(1-0) /12CO(2-1) maps made with Bure with only low resolution 5”/ 3” D configuration (to be completed soon) show unambiguously a nuclear spiral structure of average radius r=450pc and molecular gas mass Mgas= 2x109 M . • 12CO(2-1) observations resolve partly the inner spiral showing a hole near the AGN locus. • Detected strong streaming motions on the spiral will allow detail model of the gas flow. 12CO(1-0) 12CO(2-1)

  37. The supersample: beyond NUGA NUGA aims at enlarging the sample to 25-30 galaxies by adding available data on AGNs observed by consortium members. Non active galaxies are also available (comparison sample). We have compiled a tentative first list of 15 possible candidates to be included in a follow-up study.

More Related