The image-slicer, a device for reducing loss of light at slit of stellar spectrograph (Astrophysical Journal 1938)

Type Ia supernovae have played a crucial role in thediscovery of the dark energy, via the measurement of their light curvesand the determination of the peak brightness via fitting templates to theobserved lightcurve shape. Two spectroscopic indicators are also known tobe well correlated with peak luminosity. Since the spectroscopicluminosity indicators are obtained directly from observed spectra, theywill have different systematic errors than do measurements usingphotometry. Additionally, these spectroscopic indicators may be usefulfor studies of effects of evolution or age of the SNe~;Ia progenitorpopulation. We present several new variants of such spectroscopicindicators which are easy to automate and which minimize the effects ofnoise. We show that these spectroscopic indicators can be measured byproposed JDEM missions such as snap and JEDI.

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Type Ia Supernova Spectral Line Ratios as Luminosity Indicators

Integral field spectroscopy (IFS) provides a spectrum simultaneously for each spatial sample of an extended 2-D field. It consists of an integral field unit (IFU), which slices and rearranges the initial field along the entrance slit of a spectrograph. We present an original design of IFU based on the advanced image slicer concept. To reduce optical aberrations, pupil and slit mirrors are disposed in a fan-shaped configuration, which means that angles between incident and reflected beams on each element are minimized. The fan-shaped image slicer improves image quality in terms of wavefront error by a factor of 2 compared with a classical image slicer, and furthermore, it guaranties a negligible level of differential aberration in the field. As an example, we present the design LAM used for its proposal at the near-infrared spectrograph (NIRSpec/IFU) invitation of tender for the James Webb Space Telescope (JWST).

Original image slicer designed for integral field spectroscopy with the near-infrared spectrograph for the James Webb Space Telescope

A proposal of image slicer designed for integral field spectroscopy with NIRSpec/JSWT

The proposed SuperNova/Acceleration Probe (SNAP) mission will have a two-meter class telescope delivering diffraction-limited images to an instrumented 0.7 square degree field in the visible and near-infrared wavelength regime. The requirements for the instrument suite and the present configuration of the focal plane concept are presented. A two year R&D phase, largely supported by the Department of Energy, is just beginning. We describe the development activities that are taking place to advance our preparedness for mission proposal in the areas of detectors and electronics.

/pdf/snap-satellite-focal-plane-development-523urnougg.pdf

SNAP Satellite Focal Plane Development

A well-adapted spectrograph concept has been developed for the SNAP (SuperNova/Acceleration Probe) experiment The goal is to ensure proper identification of Type Ia supernovae and to standardize the magnitude of each candidate by determining explosion parameters An instrument based on an integral field method with the powerful concept of imager slicing has been designed and is presented in this paper The spectrograph concept is optimized to have very high efficiency and low spectral resolution (R {approx} 100), constant through the wavelength range (035-17{micro}m), adapted to the scientific goals of the mission

/pdf/an-integral-field-spectrograph-for-snap-supernova-studies-2sb316twmr.pdf

D.N. Kasen

Papers

An integral field spectrograph for SNAP supernova studies