Tuesday

In Active Galactic Nuclei (AGN), hot dust probes the grains closest to the black hole. At the intersection of accretion and outflow, these grains are subjected to extreme conditions. We present a sample of galaxies dominated by nuclear hot dust with little/no indication of star formation from the host galaxy contaminating the emission from the AGN. We discovered SSTISAGEMC J053444.17-673750.1 behind the LMC at redshift z ~ 1, the Spitzer IRS spectrum of which displays silicate dust emission, with negligible far-IR emission from star forming interstellar dust clouds. This source joins the hitherto unique AGN SAGE1CJ053634.78-722658.5, also behind the LMC at z ~ 0.14, that has the strongest AGN silicate emission known.
Using a dimensional reduction machine learning algorithm called t-SNE (t-distributed Stochastic Neighbourhood Embedding) with multi-wavelength photometry and astrometry from Gaia EDR3, VMC, AllWISE and ASKAP, we created a 2D map on which we discovered a further 16 objects around the position of the two unusual AGN, separated from the rest of sources. Of these sources, the majority display similar spectral energy distributions (SEDs) to the unusual AGN, for 8 of which were obtained optical spectra at SAAO, dominated by the Broad-Line Region and disk emission. We fit the SEDs with the CIGALE code, to characterise the geometry and dust properties in this sample of AGN dust dominated galaxies.