PIFS Basic Infromation
The Palomar Integral Field Spectrograph (PIFS) is a cryogenic, image slicing
spectrograph designed for use in the near-infrared, and operating on the
200-inch Telescope at
Palomar.
PIFS is best suited to
kinematic studies of emission line gas in morphologically
complex galaxies, such as ultraluminous infrared galaxies and
high-redshift radio galaxies. The all-cryogenic spectrograph
design acts as a front-end to either of two 256x256 infrared array
cameras, covering the 1-2.5 micron or 1-5 micron wavelength ranges.
Standard machining techniques, including diamond fly-cutting of the
image slicer optical surfaces, were used in the production of the
all-aluminum image slicer, allowing for an inexpensive and rapid
construction project. The 5.5x9.5 arcsecond field of view is
split into eight slits, and feeds two independent spectrographs
within the same dewar. Two resolution modes are available,
as well as a broad-band imaging mode for photometry and target
acquisition. Spectral resolutions offered are R=1300 and R=600.
The PIFS was first used on the 200-inch Telescope in 1998 September.
The performance was as predicted, with a total system throughput of
22%, enabling detection of a K=18 (0.04 mJy) continuum source at
5-sigma in one hour at the high resolution setting.
The PIFS was built chiefly for the purpose of studying ultraluminous infrared galaxies (ULIRGs), though it is also well suited to the study of emission line nebulae in high-redshift radio galaxies.
Primary funding for the PIFS came from the National Science Foundation, with additional contributions from NASA (Grad. Student Researcher Program), and private funds from Caltech.
PIFS, in essence, is eight spectrographs in one, slicing the 5.5x9.5 arcsecond field of view into eight slits, each 0.67x9.5 arcseconds in size. These eight slits are rearranged into two sets of four, each set forming an end-to-end arrangement, approximating a single long slit. See the image slicer's laser output to gain a better understanding of how the slits are arranged. Each set of four slits is passed through its own spectrometer, finally arriving at the output focal plane in the form shown in the laser spectrum.
What one has in the end is a 4x2 array of longslit-style spectra on the detector array. Data reduction is fairly straightforward in the sense that conceptually this is no harder than reducing a single longslit spectrum. It just so happens to be eight of them.
By covering a contiguous two-dimensional patch of sky (thus the term, integral field), one obtains a spectrum for every point within that field. Thus one instantly has a datacube--three dimensions of information. This technique is very powerful for studying spatially complex targets, especially those with moderate ranges of radial velocities. With this 3-d information, not only is the two-dimensional spatial distribution of line-emitting gas deduced, but also the radial velocity of the gas is measured--simultaneously answering the questions: where, and how fast?
See the very first data taken with the PIFS, of BD+30, a planetary nebula.