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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 448134.0, MPI für Astronomie / Publikationen_mpia
Molecular gas in NUclei of GAlaxies (NUGA). XI. A complete gravity torque map of NGC 4579: new clues to bar evolution
Authors:García-Burillo, S.; Fernández-Garcí­a, S.; Combes, F.; Hunt, L. K.; Haan, S.; Schinnerer, E.; Boone, F.; Krips, M.; Márquez, I.
Date of Publication (YYYY-MM-DD):2009
Title of Journal:Astronomy and Astrophysics
Journal Abbrev.:A & A
Start Page:85
End Page:105
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:In this paper we create a complete gravity torque map of the disk of the LINER/Seyfert 1.9 galaxy NGC 4579. We quantify the efficiency of angular momentum transport and search for signatures of secular evolution in the fueling process from r ~ 15 kpc down to the inner r ~ 50 pc around the active galactic nucleus (AGN). We use both the 1-0 and 2-1 line maps of 12CO obtained with the Plateau de Bure Interferometer (PdBI) as part of the NUclei of Galaxies-(NUGA)-project. The CO(1-0) and CO(2-1) PdBI maps at 2.0 arcsec × 1.3 arcsec and 1.0 arcsec × 0.6 arcsec resolution, respectively, include the short spacing correction provided by IRAM-30 m data. We derive the stellar potential from an NIR (K band) wide field image of the galaxy. The K-band image, which reveals a large-scale stellar bar and a weak nuclear oval, together with a high-resolution Hi map of NGC 4579 obtained with the Very Large Array (VLA), allow us to extend the gravity torque analysis to the outer r >= 2 kpc disk. The bulk of the gas response traced by the new CO PdBI+30 m maps of NGC 4579 presented here follows the expected gas flow pattern induced by the bar potential in the presence of two inner Lindblad resonances (ILR) at r ~ 500 pc and r ~ 1.3 kpc. The morphology of the outer disk traced by Hi suggests that the neutral gas is currently piling up in a pseudo-ring formed by two winding spiral arms that are morphologically decoupled from the bar structure. The pseudo-ring is located inside the bar corotation (r_CR ~ 6 kpc) and close to the predicted position of the ultra harmonic resonance (UHR) (r_UHR ~ 3.8 kpc). The derived gravity torque budget in NGC 4579 shows that inward gas flow is occurring on different spatial scales in the disk. In the outer disk, the decoupling of the spiral allows the gas to efficiently populate the UHR region, and thus produce net gas inflow on intermediate scales. The corotation barrier seems to be overcome by secular evolution processes. The gas in the inner disk (r <= 2 kpc) is efficiently funneled by gravity torques down to r ~ 300 pc. Closer to the AGN (r < 200 pc), gas feels negative torques due to the combined action of the large-scale bar and the inner oval. The two m=2 modes act in concert to produce net gas inflow down to r ~ 50 pc, providing clear smoking gun evidence of inward gas transport on short dynamical timescales (~1-3 rotation periods). Based on observations carried out with the IRAM Plateau de Bure Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).
Free Keywords:galaxies: individual: NGC 4579; galaxies: ISM; galaxies: kinematics and dynamics; galaxies: nuclei; galaxies: Seyfert; radio lines: galaxies
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
Identifiers:URL:http://adsabs.harvard.edu/abs/2009A%26A...496...85... [ID No:1]
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