Celebrate the Large and Long Program: Dark Energy Survey Supernova Cosmology

Celebrate the Large and Long Program! is a series of blog posts which showcase the high-impact science under the Large and Long Program of Gemini Observatory.

What is the Large and Long Program?

The Large and Long Program (LLP) is one of five observing modes Gemini offers to users of our telescopes. These five modes categorize projects based on length and weather conditions required for the observations. Classically, Gemini accepts proposals on a six month basis and recipients awarded with observing time complete their observations within that given semester. Large and Long Programs, on the other hand, provide more flexibility for long term research and last anywhere from one to three years. This extended time frame promotes collaboration across communities and produces significant and high-impact science. Here, we ask past and present Large and Long Programs to share a little about their research and experience with Gemini Observatory.

Dark Energy Survey (DES) Supernova Cosmology

1. Principal Investigator: Name and Affiliation?

Ryan Foley – University of California, Santa Cruz

2. How would you describe your Large and Long Program?

The Dark Energy Survey (DES) is a large, multi-year program that is using the CTIO 4-m Blanco telescope to map a large portion of the sky and will further our understanding of dark energy.  About a quarter of the Dark Energy Survey’s time is devoted to repeated observations for a relatively small part of the sky (30 square degrees).  In these images, we search for new stars or supernovae.  A particular type of supernova, Type Ia, are precise distance indicators, and with them, we can map the expansion history of the universe.  With our Gemini Large and Long Program, we are making sure that the supernovae are Type Ia, measuring their redshifts, and improving their calibration.  Our program is critical to the reach the goals of the entire Dark Energy Survey.

3. Why is Gemini best suited for this research?

The supernovae that we are observing are very faint, and large-aperture telescopes, like Gemini, are necessary to observe them.  Supernovae also rise and fade in a matter of weeks, and change substantially in even a few days, so Gemini’s queue, which makes it incredibly nimble, provides the most efficient observations.

4. What has been the best part of your experience with the Large and Long Program?

The Gemini staff have been incredibly helpful and responsive.  We want to observe a supernova only a few days after discovery, which requires a lot of coordination to make sure the observation happens.  Everyone at Gemini has been extremely supportive and helpful.