Hintze Centre for Astrophysical Surveys

Abstract:

<jats:title>ABSTRACT</jats:title> <jats:p>We use high-resolution data from the millimetre-Wave Interferometric Survey of Dark Object Masses (WISDOM) project to investigate the connection between circumnuclear gas reservoirs and nuclear activity in a sample of nearby galaxies. Our sample spans a wide range of nuclear activity types including radio galaxies, Seyfert galaxies, low-luminosity active galactic nuclei (AGN) and inactive galaxies. We use measurements of nuclear millimetre continuum emission along with other archival tracers of AGN accretion/activity to investigate previous claims that at, circumnuclear scales (&amp;lt;100 pc), these should correlate with the mass of the cold molecular gas. We find that the molecular gas mass does not correlate with any tracer of nuclear activity. This suggests the level of nuclear activity cannot solely be regulated by the amount of cold gas around the supermassive black hole (SMBH). This indicates that AGN fuelling, that drives gas from the large-scale galaxy to the nuclear regions, is not a ubiquitous process and may vary between AGN type, with time-scale variations likely to be very important. By studying the structure of the central molecular gas reservoirs, we find our galaxies have a range of nuclear molecular gas concentrations. This could indicate that some of our galaxies may have had their circumnuclear regions impacted by AGN feedback, even though they currently have low nuclear activity. Alternatively, the nuclear molecular gas concentrations in our galaxies could instead be set by secular processes.</jats:p>

Abstract:

ABSTRACT We present observational evidence of late-time interaction between the ejecta of the hydrogen-poor Type Ib supernova (SN) 2019yvr and hydrogen-rich circumstellar material (CSM), similar to the Type Ib SN 2014C. A narrow H α emission line appears simultaneously with a break in the light-curve decline rate at around 80–100 d after explosion. From the interaction delay and the ejecta velocity, under the assumption that the CSM is detached from the progenitor, we estimate the CSM inner radius to be located at ∼6.5–9.1 × 1015 cm. The H α emission line persists throughout the nebular phase at least up to +420 d post-explosion, with a full width at half maximum of ∼2000 km s−1. Assuming a steady mass-loss, the estimated mass-loss rate from the luminosity of the H α line is ∼3–7 × 10−5 M⊙ yr−1. From hydrodynamical modelling and analysis of the nebular spectra, we find a progenitor He-core mass of 3–4 M⊙, which would imply an initial mass of 13–15 M⊙. Our result supports the case of a relatively low-mass progenitor possibly in a binary system as opposed to a higher mass single star undergoing a luminous blue variable phase.