Hunting for Hidden Explosions with SPIRITS
Jacob Jencson, CalTech
Despite the enormous progress enabled by wide-field optical transient surveys, the census of core-collapse supernovae, even in the local 40 Mpc volume, is incomplete. Infrared searches, now systematically exploring the dynamic IR sky, offer an ideal platform to discover these missing stellar explosions. I will present results from over 4 years of SPIRITS, the Spitzer Infrared Intensive Transients Survey, an ongoing search of nearby galaxies for transients in the Spitzer/IRAC 3.6 and 4.5 micron imaging bands. We have now discovered a sample of 9 luminous infrared transients, of which 5 are likely heavily dust-extinguished core-collapse supernovae based on detailed characterizations in the optical, IR, and radio. Our results suggest as many as 38% of core-collapse supernovae are being missed in nearby galaxies. The remaining events span diverse classifications including a stellar merger, weak or electron-capture supernovae, and dust-forming, self-obscuring outbursts of massive evolved stars, suggesting that a broad array of eruptive and explosive stellar phenomena are waiting to be uncovered by new and upcoming infrared transient searches.
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Modeling the Black Hole-Galaxy Connection Over Cosmic Time
Speaker: Angelo Ricarte, Yale
Abstract: Every massive galaxy is thought to harbor a supermassive black hole at its center, but the processes by which these black holes are formed and grow to supermassive scales are not fully understood. Semi-analytic modeling offers a way to explain observed luminosity functions and empirical relations using simple physical prescriptions for black hole evolution. We find that luminosity functions for z>2 are explainable assuming only the Eddington limit, merger-triggered accretion, and a connection between black hole mass and gas supply. In addition, signatures of black hole seeding may be present in a number of observables–particularly high-redshift luminosity functions and gravitational waves–but these signatures are degenerate with uncertainties regarding either black hole accretion and dynamics. Finally, I assess the capability for black holes to explain unknown excesses in the cosmic infrared background.