We present the first interferometric observations of CO ( 1–0 ) and CO ( 2–1 ) line emission from the warped LINER NGC~3718 , obtained with the IRAM Plateau de Bure Interferometer ( PdBI ) .
This L1.9 galaxy has a prominent dust lane and on kiloparsec scales , a strongly warped atomic and molecular gas disk .
The molecular gas is closely associated with the dust lane across the nucleus and its kinematic center is consistent with the millimeter continuum AGN .
A comparison of our interferometric mosaic data , which fully cover the \sim 9 { kpc } warped disk , with a previously obtained IRAM 30 m single dish CO ( 1–0 ) map shows that the molecular gas distribution in the disk is heavily resolved by the PdBI map .
On the nucleus the interferometric maps alone contain less than one half of the single dish line flux , and the overall mosaic accounts for about a tenth of the total molecular gas mass of \sim 2.4 \times 10 ^ { 8 } \mbox { $ \mathcal { M } _ { \odot } $ } .
After applying a short-spacing correction with the IRAM 30 m data to recover the missing extended flux , we find in total six main source components within the dust lane : one associated with the nucleus , four symmetrically positioned on either side at galactocentric distances of about 1.3 kpc and 4.0 kpc from the center , and a sixth on the western side at \sim 3 { kpc } with only a very weak eastern counterpart .
In the framework of a kinematic model using tilted rings , we interpret the five symmetric source components as locations of strong orbital crowding .
We further find indications that the warp appears not only on kpc scales , but continues down to \sim 250 { pc } .
Besides the sixth feature on the western side , the lower flux ( a factor of \sim 2 ) of the eastern components compared to the western ones indicates an intrinsic large scale asymmetry in NGC 3718 that can not be explained by the warp .
Indications for a small scale asymmetry are also seen in the central 600 pc .
These asymmetries might be evidence for a tidal interaction with a companion galaxy ( large scales ) and gas accretion onto the nucleus ( small scales ) .
Our study of NGC 3718 is part of the NUclei of GAlaxies ( NUGA ) project that aims at investigating the different processes of gas accretion onto Active Galactic Nuclei ( AGN ) .