by Roberto Abraham, Karl Glazebrook, and Pat McCarthy
The Gemini
Deep Deep Survey:
The Impact Continues
After more than nine years and 13 scientific papers, the Gemini Deep Deep Survey
(GDDS) continues its legacy of scientific impact in new and surprising ways. In this
article, the three Co-PI’s share the latest results from the GDDS data set, shedding
light on the intriguing ultra-compact, massive, high-redshift galaxy population and
the identification of a 2-5-micron, near-infrared excess that could be the start of an
exciting new field — extragalactic planet formation.
If anybody had told us (the authors) nine years ago that the Gemini Deep Deep Survey (GDDS)
observations (obtained in 2003) would still be leading to papers in 2012, we’d have said they
were crazy. Yet, here we are. In this article we focus on a pair of results emerging recently from
GDDS data, developed over several papers over the last few years (Chevance et al., 2012; Damjanov et al., 2011; and Mentuch et al., 2009). These concern the intriguing “ultra-compact,” massive, high-redshift galaxy population, and the nature of a curious near-infrared (NIR) excess
seen in our star-forming sample. We will consider these in turn.
Models of galaxy formation fall into two main categories: monolithic collapse and hierarchical
merging. In the monolithic view, large galaxies formed all at once through the rapid gravitational collapse of a large gas cloud. In the hierarchical scheme, small galaxies merged gradually
over time to create larger, more massive, systems. The discovery of a puzzling new population
of compact (half-light sizes less than one kiloparsec (3,260 light-years), massive galaxies, existing at an epoch when the universe was not more than one-third of its current age, poses severe
challenges for both models.
7
GeminiFocus
June2012