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A low-luminosity type-1 QSO sample. IV. Molecular gas contents and conditions of star formation in three nearby Seyfert galaxies

Lydia Moser ; Melanie Krips ; Gerold Busch ; Julia Scharwächter ; Sabine König (Institutionen för rymd- och geovetenskap, Radioastronomi och astrofysik) ; Andreas Eckart ; Semir Smajic ; Macarena Garcia-Marin ; Monica Valencia-S. ; Sebastian Fischer ; Jens Dierkes
Astronomy and Astrophysics (0004-6361). Vol. 587 (2016), p. A137.
[Artikel, refereegranskad vetenskaplig]

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) < 1.8 kpc. 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) × 109M⊙. We give lower limits for the dynamical masses of Mdyn> 1.5 × 109M⊙ and for the dust masses of Mdust> 1.6 × 106M⊙. 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 = 50-550 M⊙pc-2 and ΣSFR = 1.1-3.1 M⊙ kpc-2 yr-1, 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.

Nyckelord: submillimeter: galaxies, radio lines: galaxies, galaxies: ISM, galaxies: active, galaxies: Seyfert, galaxies: kinematics and dynamics



Denna post skapades 2016-12-02. Senast ändrad 2017-01-20.
CPL Pubid: 245798

 

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Institutioner (Chalmers)

Institutionen för rymd- och geovetenskap, Radioastronomi och astrofysik (2010-2017)

Ämnesområden

Astronomi
Extragalaktisk astronomi

Chalmers infrastruktur