ALMA probes the molecular gas reservoirs in the changing-look Seyfert galaxy Mrk 590
Date Issued
2016
Author(s)
Abstract
We investigate if the active galactic nucleus (AGN) of Mrk 590, whose supermassive black hole was until recently highly accreting, is turning off due to a lack of central gas to fuel it. We analyse new subarcsecond resolution Atacama Large Millimetre/submilllimetre Array maps of the 12CO(3-2) line and 344 GHz continuum emission in Mrk 590. We detect no 12CO(3-2) emission in the inner 150 pc, constraining the central molecular gas mass to M(H2) ≲ 1.6 × 105 M☉, no more than a typical giant molecular gas cloud, for a CO luminosity to gas mass conversion factor of αCO ∼ 0.8 M☉ (K km s- 1 pc2)- 1. However, there is still potentially enough gas to fuel the black hole for another 2.6 × 105 yr assuming Eddington-limited accretion. We therefore cannot rule out that the AGN may just be experiencing a temporary feeding break, and may turn on again in the near future. We discover a ring-like structure at a radius of ∼1 kpc, where a gas clump exhibiting disturbed kinematics and located just ∼200 pc west of the AGN, may be refuelling the centre. Mrk 590 does not have significantly less gas than other nearby AGN host galaxies at kpc scales, confirming that gas reservoirs at these scales provide no direct indication of on-going AGN activity and accretion rates. Continuum emission detected in the central 150 pc likely originates from warm AGN-heated dust, although contributions from synchrotron and free-free emission cannot be ruled out.
Volume
455
Issue
3
Start page
2745
Issn Identifier
0035-8711
Ads BibCode
2016MNRAS.455.2745K
Rights
open.access
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