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| SparsePak | |
|---|---|
| Name | SparsePak |
| Type | Integral field unit |
| Telescope | WIYN 3.5-meter Telescope |
| Location | Kitt Peak National Observatory |
| Institution | University of Wisconsin–Madison |
| First light | 2003 |
| Wavelength | Optical |
| Fibers | 82 |
SparsePak
SparsePak is a fiber-optic integral field unit designed for intermediate-resolution spectroscopy on the WIYN 3.5-meter Telescope at Kitt Peak National Observatory. It was developed to enable two-dimensional kinematic and stellar population studies of nearby galaxies, providing enhanced surface-brightness sensitivity and spatial sampling matched to extended targets. The instrument has been used in programs connected to institutions such as the University of Wisconsin–Madison, NOIRLab, and collaborative surveys with observers from Carnegie Institution for Science and Smithsonian Astrophysical Observatory.
SparsePak provides a sparse, large-format fiber array optimized for low-surface-brightness spectroscopy of extended objects like spiral galaxies, elliptical galaxies, and dwarf galaxies. It couples to spectrographs mounted on the WIYN Telescope and was conceived to complement long-slit devices used in programs tied to the Sloan Digital Sky Survey, Hubble Space Telescope, and ground-based facilities such as the Keck Observatory and Gemini Observatory. The design emphasizes high throughput and stability for kinematic mapping useful in studies related to the Tully–Fisher relation, dark matter halo characterization, and stellar-absorption line diagnostics employed in comparisons with outputs from models by groups at Max Planck Society and Harvard–Smithsonian Center for Astrophysics.
SparsePak comprises an 82-fiber array configured in a pseudo-slit with a large patrol field to match the focal plane scale of the WIYN 3.5-meter Telescope. Fibers have core diameters selected to balance sky subtraction challenges encountered in campaigns linked to Keck LRIS and VLT FORS observations; the bundle architecture is similar in spirit to alternatives like DensePak but with larger inter-fiber spacing to increase areal coverage for programs resembling surveys by the Two Micron All Sky Survey teams. The geometry facilitates spectral resolutions comparable to echelle units used on the Subaru Telescope while coupling to spectrographs influenced by designs from the Cerro Tololo Inter-American Observatory instrumentation groups.
SparsePak interfaces with bench spectrographs through a custom fiber feed and slit assembly developed by engineers trained at institutions such as University of Wisconsin–Madison and NOAO. The instrument hardware uses polishing, alignment, and mounting techniques similar to those employed in projects at Lawrence Berkeley National Laboratory and by teams supporting the Anglo-Australian Telescope. Control and readout electronics integrate with observatory systems compatible with schedulers at Kitt Peak National Observatory and pipelines used by collaborations involving Space Telescope Science Institute investigators.
Observing with SparsePak typically involves nod-and-shuffle or beam-switching strategies analogous to procedures used on instruments like KCWI and MUSE to optimize sky subtraction for low-surface-brightness targets studied in campaigns by teams formerly associated with Palomar Observatory. Data reduction pipelines adapt methodologies from reductions developed for the Sloan Digital Sky Survey and the CALIFA project, incorporating extraction, wavelength calibration using arc lamps familiar to staff at National Optical-Infrared Astronomy Research Laboratory, and sky modeling strategies aligned with practices used by groups at European Southern Observatory. Reduction steps produce data cubes and two-dimensional velocity fields used in analyses similar to those by researchers at the University of California, Berkeley and University of Oxford.
SparsePak has been employed in kinematic studies of disk galaxies, measurement of rotation curves relevant to the Lambda-CDM framework, and determination of mass-to-light ratios underpinning comparisons with stellar-population models from teams at Max Planck Institute for Astrophysics. Programs using the instrument addressed questions about dark matter distributions in objects studied by researchers from the Carnegie Observatories and quantified ionized-gas kinematics in star-forming regions investigated by collaborators at the University of Toronto. Results informed follow-up observations by facilities including the Hubble Space Telescope and linked to theoretical efforts at institutions like the Institute for Advanced Study.
Performance characterization of SparsePak involved throughput measurements benchmarked against fiber instruments on telescopes such as Keck and Gemini, and calibration strategies used arc and continuum lamps like those standard at Kitt Peak National Observatory and were cross-checked using spectrophotometric standards observed by teams at National Optical Astronomy Observatory. Stability tests and sky-subtraction performance were validated through programs in partnership with researchers at University of Wisconsin–Madison and technicians from NOIRLab, ensuring reliable velocity measurements down to precision levels comparable to similar IFU efforts at the Anglo-Australian Observatory.
The development of SparsePak traces to instrument initiatives at the University of Wisconsin–Madison with collaborative input from staff at NOAO and a design lineage connected to fiber projects like DensePak and later integral-field efforts such as SparsePak II-style proposals. Upgrades and maintenance cycles were coordinated with observatory engineering groups at Kitt Peak National Observatory and informed by user feedback from researchers affiliated with Carnegie Institution for Science and Smithsonian Astrophysical Observatory, with occasional refurbishment activities paralleling practices at institutions like the Lawrence Livermore National Laboratory.
Category:Integral field spectrographs Category:WIYN Telescope instruments Category:Kitt Peak National Observatory