Cold molecular gas outflow encasing the ionised one in the Seyfert galaxy NGC 3281

We present ALMA CO(2-1) observations of the Seyfert 2 galaxy NGC 3281 at $\sim$ 100 pc spatial resolution. This galaxy was previously known to present a bi-conical ionised gas outflow extending to 2 kpc from the nucleus. The analysis of the CO moment and channel maps, as well as kinematic modelling reveals two main components in the molecular gas: one rotating in the galaxy plane and another outflowing and extending up to $\sim$ 1.8 – 2.6 kpc from the nucleus, partially encasing the ionised component. The mass of the outflowing molecular gas component is $M_{\mathrm{m}\mathrm{o}\mathrm{l},\mathrm{o}\mathrm{u}\mathrm{t}}$ = $(2.5\pm 1.6)\times {10}^6$ ${\mathrm{M}}_{\odot }$, representing $\sim$ 1.7 – 2 % of the total molecular gas seen in emission within the inner 2.3 kpc. The corresponding mass outflow rate and power are ${\dot{M}}_{\mathrm{m}\mathrm{o}\mathrm{l},\mathrm{o}\mathrm{u}\mathrm{t}}$ = 0.12 – 0.72 ${\mathrm{M}}_{\odot }\mathrm{y}{\mathrm{r}}^{-1}$ and ${\dot{E}}_{\mathrm{m}\mathrm{o}\mathrm{l},\mathrm{o}\mathrm{u}\mathrm{t}}$ = (0.045 – 1.6) $\times {10}^{40}$ $\mathrm{e}\mathrm{r}\mathrm{g}{\mathrm{s}}^{-1}$, which translates to a kinetic coupling efficiency with the AGN power of only ${10}^{-4}$ – 0.02 %. This value reaches up to 0.1 % when including both the feedback in the ionised and molecular gas, as well as considering that only part of the energy couples kinetically with the gas. Some of the non-rotating CO emission can also be attributed to inflow in the galaxy plane towards the nucleus. The similarity of the CO outflow – encasing the ionised gas one and the X-ray emission – to those seen in other sources, suggests that this may be a common property of galactic outflows.