Susanne Aalto (Chalmers U.): "Thick as Thieves - Unveiling the Most Compact and Obscured Galaxy Nuclei"


Cold gas plays a central role in feeding and regulating star formation and growth of supermassive black holes (SMBH) in galaxy nuclei. Particularly powerful activity occurs when interactions of gas-rich galaxies funnel large amounts of gas and dust into nuclei of luminous and ultra luminous infrared galaxies (LIRGs/ULIRGs). These dusty objects are of key importance to galaxy mass assembly over cosmic time. Dust embedded galaxy evolution also occurs in less extreme galaxies – including nearby starbursts or enshrouded AGNs. Studying them is fundamental to our understanding of how galaxies evolve in the Universe.

Some (U)LIRGS have deeply embedded galaxy nuclei that harbour a particularly active evolutionary stage of AGNs and/or starbursts: the Compact Obscured Nuclei (CONs). The nuclear activity drives mechanical feedback in the form of molecular winds, jets and outflows.  This feedback can remove baryons from low-mass galaxies, prevent overgrowth of galaxies, explain “red-and dead” properties of local ellipticals, and be linked to the M-sigma relation. With mm/submm to FIR and IR telescopes,  we can study the morphology, velocity structure, physical conditions and even chemistry of the obscured nuclei and their cold flows at unprecedented sensitivity and resolution.  We have found a new feedback phase that may support nuclear accretion.

I will focus on recent ALMA,  NOEMA and jWST studies of enshrouded nuclei, AGN and feedback.  ALMA studies  (resolution 0.”02 (1 – 7 pc)), reveal launch regions of molecular outflows, inflows, and dusty nuclei of  the nearby LIRGs NGC1068, NGC1377 and IC860.  The outflows are different from each other where NGC1068 shows gas carried out by a radio jet, NGC1377 has a 150 pc scale radio-quiet molecular jet, and the IC860 flow is exceedingly compact and dense. I will also discuss how vibrationally excited molecular emission (e.g. HCN) can reach behind the curtain of dust to undertake new studies of heretofore hidden, rapid evolutionary phases of galaxy nuclei. Do CONs represent a new, unknown evolutionary phase of galactic growth?


Date: 12:15 PM, May 17th, 2023
Location: Online only, please visit to sign up to get talk announcements with Zoom URLs.
Category: Science Talk