Cake Talk: Kevin Jun Yi Koay

Time: Thursday May 12th, 14:00 (25min talk)

Place: DARK Lounge

Title: The curious case of the changing-look Seyfert galaxy, Mrk 590

Abstract: Sometime between the years 2006 and 2012, the broad Hβ emission line of Mrk 590, once classified as a Seyfert 1 galaxy, has completely disappeared! The optical-UV continuum emission has faded to the point where it can be fully accounted for by the host galaxy starlight. As such, Mrk 590 would now be classified as a Seyfert 1.9 or 2 galaxy, which goes against the prevailing scheme of AGN classification and unification where the presence of broad emission lines depends only on source orientation. Similar decreases in X-ray and radio continuum fluxes suggest that the central engine of Mrk 590 may be turning off or transitioning into a radiatively inefficient mode of accretion. I will talk about the origin of the compact, unresolved radio emission in Mrk 590 and the physical nature of its variability in relation to the variability observed at other wavelengths, based on archival radio data and new VLBI observations. I will also present recent CO line observations with ALMA, which provide the strongest limits to date on the molecular gas mass in the central regions, to determine if this AGN is running out of gas to fuel it.