GeminiFocus October 2018 - Page 5

Mark Lacy, Kristina Nyland, and Susan Ridgway GeMS Delivers the Sharpest View of the Visible Light from Distant Galaxies We recently used GeMS/GSAOI observations to make some of the first ≈ 0.1-arcsecond-resolution observations in the near-infrared of extragalactic fields exceeding 1.5 arcminutes in size. The unique capabilities of GeMS have allowed us to study the size evolution of distant galaxies in the rest-frame optical/near-infrared. In particular we have focused on z ~ 1-3 ultraluminous infrared galaxies, finding signs of recent merger activity, including a rare candidate triple active galactic nucleus. Our observations give us an indication of what the James Webb Space Telescope will be able to deliver in a few years. Figure 1. The GSAOI image of the ES1C field. Objects of interest are shown as insets, each measuring 6 arcseconds on a side. The red circles indicate the stars used to determine the PSF in the field, and the blue circles show those used as natural guide stars for the adaptive optics system (one is off the image). The most massive galaxies seen today started life as some of the first structures to form in the early Universe, then grew both in mass and size through mergers and the accretion of further mate- rial. Along that evolutionary journey, most of them went through episodes of violent activity, including powerful starburst and quasar events. Today, most of them are quiescent in nature, with star forma- tion having largely stopped, and active galactic nu- clei (AGN) reduced to a very low level. Their story is therefore rich in astrophysical phenomena, offering us insights into what drives, and, ultimately, what stops the formation of galaxies. October 2018 GeminiFocus 3