October 2018
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.
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 material. 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 formation having largely stopped, and active galactic nuclei
(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.
Determining the physical mechanisms by which massive galaxies evolve into the objects
we see today requires imaging high-z galaxies on scales less than 1 kiloparsec (kpc). Imag-
ing in the rest-frame optical/near-infrared — longward of the Balmer break at 3646 Ång-
stroms, where the stellar population is dominated by the older stars that contribute most
of the stellar mass in a galaxy — is particularly valuable.
8
GeminiFocus
January 2019 / 2018 Year in Review