Megaprime Science Introduction

J. B. Hutchings

Dominion Astrophysical Observatory
Herzberg Institute of Astrophysics, NRC
Electronic-mail: john.hutchings@hia.nrc.ca

Abstract:

Wide field cameras UH8K and CFHT12K are in high demand. However, they are not nearly as efficient and effective as they might be. This has led to the adoption of the Megaprime project, which is a major rework of the prime focus imaging capability. This new camera and environment will place CFHT in a unique position to perform high quality very wide field imaging in the 8m telescope era.

Programs

Many current programs have overlap in sky coverage or science goals:

• Cosmology surveys
• Weak lensing studies
• Individual nearby galaxies
• Galaxy clusters
• Star clusters
• Solar system objects

There has been duplication among several of these in science goals and in target fields. We need to work towards defining and sharing data for different purposes rather than wasting telescope time in duplication.

Operations

Use of large camera has been inefficient in telescope use and data handling. We are designing the new equipment to involve the following processes as well as new hardware.

• Optimum use of observing windows (season, seeing, weather)
• Observing efficiency (fast read, auto-focus)
• Common calibration frames
• Data handling, storage, and distribution
• Data processing pipeline
• Data release and archiving

Hardware

To be effective and scientifically competitive, the new camera will have the following, based on the science workshop in Toronto in 1997:

• Unique 1.2 degree field, with 40 $2k \times 4k$ CCDs
• Sensitivity well below 4000 Å: optics and CCDs
• 0.5'' or better image quality with fast tip-tilt plate

The following talks will describe these design features in detail. Other hardware considerations not implemented after study were Atmospheric Dispersion Corrector and Grism or Grens.

The ADC will improve only short wavelength data at large hour angles, while degrading other data because of optical difficulties in this large field. The grens introduces problems and performance degradation of guiding capability in un-dispersed imaging. Full reports of these decisions are available in SAC and Megaprime web documents.

Science Programs

Major programs require careful planning and coordination among a wide group of participants. Some discussed during the workshop in Toronto last year are listed below. We need to organise teams to define such programs and decide on how to schedule them:

• Large shallow survey 1000 sq degrees
• Smaller deep survey 25 sq deg
• Weak lensing mapping of dark matter
• Supernova searches
• XMM survey follow-up
• Microlensing surveys
• Local group galaxy haloes, stellar pops, cluster systems
• Large stellar clusters
• Low surface brightness galaxies
• Kuiper belt object searches
• Distance scale calibrators in nearby galaxies
• Galaxy cluster searches

In the next year we will define the process for allocating time for large programs, and scientists will need to decide on working groups of common or compatible interest to make up the detailed observing programs, and make effective use of the data. Ideas to the CFHT web site will be welcomed, as well as the discussions at this meeting.