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The earliest generations of stars were produced in galaxies at high redshift. The physical conditions in which these stars formed, produced heavy elements and dust, and subsequently ended their life cycles, however, are vastly different from those in the Milky Way. Nearby low metal-abundance galaxies provide critical laboratories within which it is possible to observe conditions similar to those at high redshift, shedding light on the lifecycle of dust and metals in the early Universe. Does the process of star formation change at low metallicity? How did galaxies in the early Universe produce significant amounts of dust without the elapsed time necessary for stars to evolve to the asymptotic giant branch (AGB) phase and contribute via mass loss? Here we present work cataloging dust-producing sources in the nearby metal-poor galaxy NGC 6822 and outline forthcoming GTO observations of this system and the blue compact dwarf I Zw 18 with JWST.

We aim to analyse the co-added Herschel images of various categories of evolved stars in the LMC and SMC from the Herschel HERITAGE survey in order to identify, in a statistical sense, a cool historic dust mass component emitted by these sources. The fluxes derived from the co-added stacks can then be compared with those predicted by the GRAMS model grid in order to refine the DPRs estimated for the SMC and LMC.

We present JHK observations of the metal-poor $$(\left[ {{\rm{Fe}}/{\rm{H}}} \right] < - 1.40)$$ dwarf-irregular galaxies, Leo A and Sextans A, obtained with the WIYN High-resolution Infrared Camera. Their near-IR stellar populations are characterized by using a combination of color-magnitude diagrams and by identifying long-period variable (LPV) stars. We detected red giant and asymptotic giant branch (AGB) stars, consistent with membership of the galaxy’s intermediate-age populations (2-8 Gyr old). We identify 32 dusty evolved stars in Leo A and 101 dusty stars in Sextans A, confirming that metal-poor stars can form substantial amounts of dust. We also find tentative evidence for oxygen-rich dust formation at low metallicity, contradicting previous models that suggest oxygen-rich dust production is inhibited in metal-poor environments. The majority of this dust is produced by a few very dusty evolved stars.

We analyze the dust emission features seen in Spitzer Space Telescope Infrared Spectrograph (IRS) spectra of red supergiant (RSG) and oxygen-rich asymptotic giant branch (AGB) stars in the Large Magellanic Cloud and Small Magellanic Cloud galaxies and in various Milky Way globular clusters. The spectra come from the Spitzer Legacy program SAGE-Spectroscopy (PI: F. Kemper), the Spitzer program SMC-Spec (PI: G. Sloan), and other archival Spitzer-IRS programs. The broad 10 and 20 micron emission features attributed to amorphous dust of silicate composition seen in the spectra show evidence for systematic differences in the centroid of both emission features between O-rich AGB and RSG populations. Radiative transfer modeling using the GRAMS grid of models of AGB and RSG stars suggests that the centroid differences are due to differences in dust properties. We investigate differences in dust composition, size, shape, etc that might be responsible for these spectral differences. We explore how these differences may arise from the different circumstellar environments around RSG and O-rich AGB stars and assess effects of varying metallicity (LMC versus SMC versus Milky Way globular cluster) and other properties (mass-loss rate, luminosity, etc.) on the dust originating from these stars. BAS acknowledges funding from NASA ADAP grant NNX13AD54G.

We present results from a survey of the properties of the central black holes in nearby AGN. This shows that AGN radiating near Eddington are on average less massive now than at z ~ 1.