Astronomy and Astrophysics, volume 587A, 137-137 (2016/3-1)
A low-luminosity type-1 QSO sample. IV. Molecular gas contents and conditions of star formation in three nearby Seyfert galaxies.
MOSER L., KRIPS M., BUSCH G., SCHARWAECHTER J., KOENIG S., ECKART A., SMAJIC S., GARCIA-MARIN M., VALENCIA-S. M., FISCHER S. and DIERKES J.
Abstract (from CDS):
We present a pilot study of ∼3'' resolution observations of low CO transitions with the Submillimeter Array in three nearby Seyfert galaxies, which are part of the low-luminosity quasi-stellar object (LLQSOs) sample consisting of 99 nearby (z=0.06) type-1 active galactic nuclei (AGN) taken from the Hamburg/ESO quasi-stellar object (QSO) survey. Two sources were observed in 12CO(2-1) and 13CO(2-1) and the third in 12CO(3-2) and HCO+(4-3). None of the sources is detected in continuum emission. More than 80% of the 12CO detected molecular gas is concentrated within a diameter (FWHM)<1.8kpc. 13CO is tentatively detected, while HCO+ emission could not be detected. All three objects show indications of a kinematically decoupled central unresolved molecular gas component. The molecular gas masses of the three galaxies are in the range Mmol=(0.7-8.7)x109M☉. We give lower limits for the dynamical masses of Mdyn>1.5x109M☉ and for the dust masses of Mdust>1.6x106M☉. The R21=12CO/13CO(2-1) line luminosity ratios show Galactic values of R21∼5-7 in the outskirts and R21>20 in the central region, similar to starbursts and (ultra)luminous infrared galaxies ((U)LIRGs; i.e. LIRGs and ULIRGs), implying higher temperatures and stronger turbulence. All three sources show indications of 12CO(2-1)/12CO(1-0) ratios of ∼0.5, suggesting a cold or diffuse gas phase. Strikingly, the 12CO(3-2)/(1-0) ratio of ∼1 also indicates a higher excited phase. Since these galaxies have high infrared luminosities of LIR≥1011L☉ and seem to contain a circumnuclear starburst with minimum surface densities of gas and star formation rate (SFR) around Σmol=50-550M☉/pc2 and ΣSFR=1.1-3.1M☉/kpc2/yr, we conclude that the interstellar medium in the centers of these LIRG Seyferts is strongly affected by violent star formation and better described by the ULIRG mass conversion factor.
submillimeter: galaxies - radio lines: galaxies - galaxies: ISM - galaxies: active - galaxies: Seyfert - galaxies: kinematics and dynamics
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