2005A&A...441.1011G


Query : 2005A&A...441.1011G

2005A&A...441.1011G - Astronomy and Astrophysics, volume 441, 1011-1030 (2005/10-3)

Molecular gas in NUclei of GAlaxies (NUGA). IV. Gravitational torques and AGN feeding.

GARCIA-BURILLO S., COMBES F., SCHINNERER E., BOONE F. and HUNT L.K.

Abstract (from CDS):

We discuss the efficiency of stellar gravity torques as a mechanism to account for the feeding of the central engines of four low luminosity Active Galactic Nuclei (AGN): NGC 4321 (HII nucleus/LINER), NGC 4826 (HII nucleus/LINER), NGC 4579 (LINER 1.9/Seyfert 1.9) and NGC 6951 (Seyfert 2). These galaxies have been observed as part of the NUclei of GAlaxies-(NUGA) CO project, aimed at the study of AGN fueling mechanisms. Our calculations allow us to derive the characteristic time-scales for gas flows and discuss whether torques from the stellar potentials are efficient enough to drain the gas angular momentum in the inner 1kpc of these galaxies. The stellar potentials are derived using high-resolution near infrared (NIR) images and the averaged effective torques on the gas are estimated using the high-resolution (∼0.5"-2") CO maps of the galaxies.
Result. indicate paradoxically that feeding should be thwarted close to the AGNs: in the four cases analyzed, gravity torques are mostly positive inside r∼200pc, resulting in no inflow on these scales. As a possible solution for the paradox, we speculate that the agent responsible for driving inflow to still smaller radii is transient and thus presently absent in the stellar potential. Alternatively, the gravity torque barrier associated with the Inner Lindblad Resonance of the bars in these galaxies could be overcome by other mechanisms that become competitive in due time against gravity torques. In particular, we estimate on a case-by-case basis the efficiency of viscosity versus gravity torques to drive AGN fueling. We find that viscosity can counteract moderate-to-low gravity torques on the gas if it acts on a nuclear ring of high gas surface density contrast and ∼a few 100pc size. We propose an evolutionary scenario in which gravity torques and viscosity act in concert to produce recurrent episodes of activity during the typical lifetime of any galaxy. In this scenario the recurrence of activity in galaxies is indirectly related to that of the bar instabilities although the active phases are not necessarily coincident with the maximum strength of a single bar episode. The general implications of these results for the current understanding of fueling of low-luminosity AGN are discussed.

Abstract Copyright:

Journal keyword(s): galaxies: individual: NGC 4321, NGC 4579, NGC 4826, NGC 6951 - galaxies: ISM - galaxies: kinematics and dynamics - galaxies: nuclei - galaxies: Seyfert - radio lines: galaxies

Nomenclature: Figs 1-4: [GCS2005] JHHMMSS.ss+DDMMSS.s N=4.

Simbad objects: 14

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Number of rows : 14
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
#notes
1 3C 84 Sy2 03 19 48.1599902040 +41 30 42.108850836   13.10 12.48 11.09   ~ 3892 3
2 QSO B0420-0127 QSO 04 23 15.80072217 -01 20 33.0656073   17.50 17.00 16.28   ~ 1163 3
3 RAFGL 618 pA* 04 42 53.6242032600 +36 06 53.400902220   16.32   12.59   C-rich 991 0
4 QSO B0607-157 QSO 06 09 40.94954062 -15 42 40.6727537   18.47 18.00 19.90   ~ 306 1
5 QSO J0730-116 QSO 07 30 19.11247452 -11 41 12.6006642     20.30 20.3   ~ 286 1
6 M 100 AGN 12 22 54.9299993592 +15 49 20.296257960 10.04 10.05 9.35     ~ 1780 2
7 M 58 SyG 12 37 43.597 +11 49 05.12 10.80 10.48 9.66     ~ 1044 2
8 [HU2001] J203714.118+660620.02 Rad 12 56 43.64 +21 40 59.1           ~ 2 0
9 M 64 SyG 12 56 43.696 +21 40 57.57   9.36 8.52     ~ 902 2
10 NGC 5953 GiP 15 34 32.402 +15 11 37.80   13.23 12.45     ~ 359 1
11 EM* MWC 349 ** 20 32 45.499080 +40 39 36.74124   15.88 13.15 12.13   Bep 779 0
12 NGC 6951 Sy2 20 37 14.1228088488 +66 06 20.049916392   11.64 10.65     ~ 516 2
13 NGC 7217 LIN 22 07 52.3984675584 +31 21 33.632293572   12.94 11.92     ~ 482 0
14 3C 454.3 Bla 22 53 57.7480438728 +16 08 53.561508864   16.57 16.10 15.22   ~ 2753 2

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2023.06.03-10:28:21

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