CanariCam is the facility multi-mode mid-IR camera developed by the University of Florida for the 10-meter Gran
Telescopio Canarias (GTC) on La Palma. CanariCam has four science modes that provide the GTC community with an
especially powerful research tool for imaging, grating spectroscopy, coronagraphy, and dual-beam polarimetry.
Instrument commissioning in the laboratory at the University of Florida indicates that all modes perform as required, and
the next step is on-telescope commissioning. After commenting on the instrument status, we will review key features of
each of these science modes, with emphasis on illustrating each mode with science examples that put the system
performance, particularly the anticipated sensitivity, into perspective.
Mid-infrared polarimetry remains an underexploited technique; where available it is limited in spectral coverage from
the ground, and conspicuously absent from the Spitzer, JWST and Herschel instrument suites. The unique characteristics
of SOFIA afford unprecedented spectral coverage and sensitivity in the mid-infrared waveband. We discuss the
preliminary optical design for a 5-40μm spectro-polarimeter for use on SOFIA, the SOFIA Mid-InfraRed Polarimeter
(SMIRPh). The design furthers the existing 5-40μm imaging and spectroscopic capabilities of SOFIA, and draws on
experience gained through the University of Florida's mid-IR imagers, spectrometer and polarimeter designs of T-ReCS
and CanariCam. We pay special attention to the challenges of obtaining polarimetric materials suitable at both these
wavelengths and cryogenic temperatures. Finally, we (briefly) present an overview of science highlights that could be
performed from a 5-40μm imaging- and spectro-polarimeter on SOFIA. Combined with the synergy between the
possible future far-IR polarimeter, Hale, this instrument would provide the SOFIA community with unique and exciting
science capabilities, leaving a unique scientific legacy.
CanariCam is the facility multi-mode mid-IR camera developed by the University of Florida (UF) for the 10.4-
meter Gran Telescopio Canarias (GTC). CanariCam contains a 320 × 240-pixel Raytheon array, which will
Nyquist-sample the diffraction-limited point-spread-function at wavelengths longer than 8 microns, yielding a
field of view of 26"×19". In Aug. 2007, the University of Florida instrument team held a successful Acceptance
Testing (AT) of CanariCam. We describe key performance requirements, and compare these to the actual performance
during formal AT. Among the results considered are detector noise characteristics, image quality, and
throughput. We focus particularly on the unique dual-beam polarimetric modes. We have demonstrated that
with a half-wave plate, it achieves or exceeds the design goals for imaging both polarization planes simultaneously.
Mid-infrared polarimetry remains an underexploited technique; where available it is limited in spectral coverage from
the ground, and conspicuously absent from both the Spitzer and JWST instrument suites. The unique characteristics of
SOFIA affords unprecedented spectral coverage and sensitivity in the mid-infrared waveband, offering new vistas in the
exploration of astrophysical objects, including (a) galaxies and AGN, (b) star formation regions and (c) debris disks.
Furthering the existing 5-40μm imaging and spectroscopic capabilities of SOFIA, and the University of Florida's mid-IR
imagers, spectrometer and polarimeter designs of T-ReCS and CanariCam, we present an overview of science highlights
that could be performed from a ~5-40μm imaging- and spectro-polarimeter on SOFIA. A secondary science driver is the
inclusion of low- to moderate- resolution (total flux) spectroscopy at these wavelengths. Such an instrument concept
would plug an unfilled area of both SOFIA and space-based instrumentation, providing SOFIA with unique and exciting
science capabilities.
Direct detection of the light scattered from extra-solar planets is important in establishing the planet's mass, radius, albedo and nature of the particles in the planetary atmosphere. We describe, and present results from, a new optical polarimeter (PlanetPol) designed to reach fractional polarizations of 10-6 or better from ground-based telescopes, necessary to detect the polarization signature of unresolved hot-Jupiters.
We describe a polarimeter for the near-infrared camera SIRIUS mounted on the IRSF 1.4 m telescope in South Africa. The polarimeter, SIRPOL, consists of an achromatic (1-2.5 μm) wave plate rotator unit and a polarizer located upstream of the camera, both of which are at a room temperature. This minimizes the effect of the mirrors in the camera on instrumental polarization. The combination of the polarimeter with the SIRIUS camera enables a deep (J = 19.2 mag, 5σ in one hour) and wide-field (7.7' × 7.7') imaging polarimetry at JHKs simultaneously. The three color near-infrared polarimetry is useful for understanding the properties of dust grains that cause scattering and absorption in various environments (e.g., star forming regions, late-type stars, and galaxies). Using IRSF and SIRPOL, wide-field near-infrared polarization surveys in various star-forming regions are being conducted, starting from 2006, which aim to study both reflection nebulae associated with young stars and interstellar polarizations of background stars. In this contribution, we describe the hardware and software of SIRPOL and report its first results on the telescope.
The University of Florida is developing a mid-infrared camera for the 10.4-meter Gran Telescopio CANARIAS. CanariCam has four science modes and two engineering modes, which use the same 320 x 240-pixel, arsenic-doped silicon, blocked-impurity-band detector from Raytheon. Each mode can be remotely selected quickly during an observing sequence. The pixel scale is 0.08 arcsec, resulting in Nyquist sampling of the diffraction-limited point-spread-function at 8 μm, the shortest wavelength for which CanariCam is optimized. The total available field of view for imaging is 26 arcsec x 19 arcsec. The primary science mode will be diffraction-limited imaging using one of several available spectral filters in the 10 μm (8-14 μm) and 20 μm (16-25 μm) atmospheric windows. Any one of four plane gratings can be inserted for low and moderate-resolution (R = 100 - 1300) slit spectroscopy in the 10 and 20-μm regions. Insertion of appropriate field and pupil stops converts the camera into a coronagraph, while insertion of an internal rotating half-wave plate, a field mask, and a Wollaston prism converts the camera into a dual-beam polarimeter.
Gemini polarimetry is based on a waveplate module located in the base of the A&G unit that can be used by all instruments operating in the optical and near-infrared. Because of space limitations and limited access to the module, a single half-wave retarder covering 0.34 to 2.5μm is used for linear polarimetry. A composite zero-order half-wave retarder is used for the L-band (mid-IR instruments have their own waveplate module). The plates have a clear aperture of 95mm and are surrounded by a transparent annulus to increase the field of view for the on-instrument wavefront sensors. Each instrument includes, or will include, a 2-beam polarising prism, usually in the form of a Wollaston prism. Provision for circular polarimetry has been included but not yet implemented. The design of the waveplate module and the techniques employed to provide high precision are described. The materials available for the Wollaston prisms, including those used in the mid-IR, are also discussed. Techniques to avoid ripple in the polarisation spectrum observed with some spectrometers are presented. Unfortunately at present observational results are not available to include in this paper.
We have carried out KHL band high resolution imaging and H band imaging-polarimetry of the Red Rectangle nebula using CIAO and 36 element AO mounted on the 8.2m Subaru telescope. HK band images show a X-shape structure close to 0.1 inch and 2 lobes with separation of 0.15 inch at the north and the south. Our L band image show a small clump and its position is 0.1 arcsec east from the center of the southern lobe. The polarization map shows roughly centrosymmetric vector pattern and the center of the pattern is consistent with that of 2 lobes. There is scatter of the vector pattern at approximately 0.1 inch east from the southern lobe and a local minimum in the degree of polarization. These results can explain that the primary star HD44179 is at 0.1 inch east from the southern lobes and the dominant illumination source is a M type star at the center of the nebula.
We are constructing a high sensitivity optical polarimeter capable of detecting fractional polarization levels below 10-6. The science goal is to directly detect extra-solar planets (ESP), in contrast to the indirect methods such as radial velocity measurements. The polarimeter will detect starlight scattered from the atmosphere of the planet as a polarisation signal thereby giving information on the planetary atmospheres. The radius of the planet and the planet temperature can be determined from the measured albedo. The position angle of polarisation will enable the mass of planets, detected through radial velocity measurements, to be determined without the uncertainty of the orbit inclination (Msini). The polarimeter has an essentially simple and classical design but is able to take advantage, inter alia, of modern detector technology.
Polarimeters at optical and near-IR wavelengths are increasingly available as part of facility instruments at major observatories, and are used for a large number of astronomical programs, ranging form nearby star-forming regions to high-redshift galaxies. Polarimetry is used in both imaging and spectroscopic modes and at both low and high spectral resolutions. As degrees of polarization are usually low a large collecting area is needed to get the high signal to noise required for accurate polarimetry. Thus polarimetry can take particular advantage of the new generation 8m telescopes such as Gemini. Techniques for obtaining high precision measurements used for IR polarimeters on UKIRT and on the AAT, together with the performance achieved for both imagers and spectrometers are presented. The implementation of the same techniques proposed for Gemini instruments is described.
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