On-Going Instrumentation: IR Coronograph/Imager

1-5µm imaging will be a "workhorse" capability for Gemini, exploiting the superb image quality and extremely low emissivity of the telescopes. Furthermore, Gemini will be a unique platform for coronagraphic observations because of the exceptionally smooth primary mirror, rigorous mirror cleaning program, thin secondary vanes, and small telescope obscuration ratio.

Performance Guidelines for the IR Coronagraph Imager:

• Wavelength range: 0.8-5µm
• Pixel scales: 0".01, 0".02, 0".05
• Array format(s): 1kx1k with goal of 2kx2k
• Optimized coronagraphic mode
• Assume facility AO
• Near IR On Instrument WFS (OIWFS) for tip/tilt and fast focus correction
• Studies to evaluate coronagraphic performance and mask requirements and consider role of AOWFS within instrument.

Science Illustrations:

A small field imager with pixel scales and optics designed to exploit AO performance and tip/tilt corrected images with optimized near-IR coronagraphic imaging capability will address a very wide range of science topics. Not only will the Gemini Telescopes and this imager provide some of the clearest views yet of the most distant galaxies, they offer a golden opportunity to search for the faintest and most elusive of nearby objects, brown dwarfs and planets. A high performance coronagraph on Gemini would allow a statistically significant census of brown dwarf companions to distances of ~100 parsec. Any detections of low-mass companions would provide precise astrometry which, with radial velocities, would yield masses, absolute magnitudes, and temperatures, all basic to understanding the sub-stellar mass function, and ultimately the transfer of angular momentum in star formation, and the universal proportion of matter bound up in sub-stellar companions.

An AO optimized IR imager with coronagraphic capability is essential for observing high contrast ratio scenes in star formation regions, including YSO envelopes, the origins of outflows, and studies of disks and superplanets around forming stars. High spatial resolution imaging in spectral lines probing shock-ionized gas (e.g. [FeII] 1.6 microns) will enable observation of energetic jets emerging from the inner regions of accretion disks and the shocked regions which mark the interaction between jets and/or neutral winds and circumstellar material. Such observations are critical to understanding the role played by high energy outflows in terminating infall and determining stellar masses. High angular resolution is crucial in order to probe regions 5-10 AU from the stellar surface - where the wind/cloud interactions should be revealed.

Research on nearby galaxies would benefit greatly from AO systems which are capable of at least moderate Strehl ratio imaging in the near IR. The centers of galaxies are the sites of two of the most widely-studied phenomena in astrophysics: starbursts and AGN. These two mechanisms for energy generation power the high luminosities of several celebrated classes of galaxies - "ultra-luminous infrared" galaxies, Seyfert galaxies, "radio" galaxies, and quasars. However, despite intensive and voluminous studies over the past two decades, most of the fundamental issues and controversies remain unresolved. A proper exploration of compact, dusty astrophysical systems also requires the best-possible angular resolution near-IR imaging.

Last update June 5, 1998; Ruth A. Kneale