Kavli Affiliate: Claudio Ricci
| First 5 Authors: Boy Lankhaar, Susanne Aalto, Clare Wethers, Javier Moldon, Rob Beswick
| Summary:
High resolution (0."037-0."13 [10-35 pc]) e-MERLIN ($lambda6-18$ cm) and
(0."024 [6.5 pc]) ALMA ($lambda 1.1$ mm) observations have been used to image
OH (hydroxyl) and H$_2$CO (formaldehyde) megamaser emission, and HCN 3->2
emission towards the nuclear (<100 pc) region of the luminous infrared galaxy
Zw049.057. Zw049.057 hosts a compact obscured nucleus (CON), thus representing
a class of galaxies that are often associated with inflow and outflow motions.
Formaldehyde megamaser emission is detected towards the nuclear region, <30 pc
(<0."1), and traces a structure along the disk major axis. OH megamaser (OHM)
emission is detected along the minor axis of the disk, ~30 pc (0."1) from the
nucleus, where it exhibits a velocity gradient with extrema of -20 km/s
south-east (SE) of the disk and -110 km/s north-west (NW) of the disk. HCN 3->2
emission reveals extended emission, along the disk minor axis out to ~60 pc
(0."2). Analysis of the minor axis HCN emission reveals high-velocity features,
extending out to 600 km/s, redshifted on the SE side and blueshifted on the NW
side. We propose that the high-velocity HCN emission traces a fast >250 km/s
and collimated outflow, that is enveloped by a wide-angle and slow ~50 km/s
outflow that is traced by the OHM emission. Analysis of the outflow kinematics
suggests that the slow wide-angle outflow will not reach escape velocity and
instead will fall back to the galaxy disk, evolving as a so-called fountain
flow, while the fast collimated outflow traced by HCN emission will likely
escape the nuclear region. We suggest that the absence of OHM emission in the
nuclear region is due to high densities there. Even though OHMs associated with
outflows are an exception to conventional OHM emission, we expect them to be
common in CON sources that host both OHM and H$_2$CO megamasers.
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