Circumnuclear Molecular Gas Reservoirs in Mrk 590, a Seyfert Galaxy in Transition

Sometime between 2006 and 2012, the broad H beta emission line of Mrk 590 (Fig. 1, left), once classified as a bona-fide Seyfert 1 galaxy, has completely disappeared (Denney et al. 2014). The optical-UV continuum emission has decreased to the point where it can be fully accounted for by stellar population models of the host galaxy. As such, Mrk 590 would now be classified as a Seyfert 1.9 or 2, which goes against the prevailing scheme of AGN classification and unification where the presence of broad emission lines depends only on source orientation. This type-transitioning could be due to a lack of nuclear gas to fuel the central engine. If the gas in the very center is not replenished, the accretion activity ceases, and the black hole is starved and turns quiescent. We have obtained ALMA Cycle 2 observations of the (CO)-C-12(3-2) line emission to determine the amount of nuclear molecular gas available and the gas transport mechanisms (or lack thereof) responsible for feeding its central black hole.