Source-linked AI summary
PypeIt: The Python Spectroscopic Data Reduction Pipeline
J. Xavier Prochaska, Joseph F. Hennawi, Kyle B. Westfall, Ryan J. Cooke, Feige Wang, Tiffany Hsyu, Frederick B. Davies, Emanuele Paolo Farina
TL;DR
Spectroscopic data reduction requires a broadly applicable but configurable workflow that can handle diverse instruments and observing modes. PypeIt provides semi-automated frame classification, calibration, extraction, sky subtraction, and standardized outputs; it reports Poisson-limited sky subtraction and supports many spectrographs. The release remains bounded by its current instrument coverage and depends on appropriate calibration frames.
Problem
Astronomers need a semi-automated reduction package for diverse spectroscopic data, with documented parameters and functionality supporting different instruments and observing modes.
Method
PypeIt automatically classifies raw frames, applies configurable calibration and reduction algorithms, performs object extraction and two-dimensional sky subtraction, and writes standardized one- and two-dimensional outputs.
Results
PypeIt achieves Poisson-limited sky subtraction and produces fully reduced one- and two-dimensional spectra across the spectrographs supported by release v1.0.3.
Takeaways & Limitations
PypeIt provides an end-to-end, documented reduction workflow intended for both experienced spectroscopists and astronomers without prior reduction experience.
Takeaways & Limitations
The release has a defined set of supported spectrographs and requires suitable calibration frames for successful reduction.
Abstract
from arXiv · showhide
PypeIt is a Python package for semi-automated reduction of astronomical, spectroscopic data. Its algorithms build on decades-long development of previous data reduction pipelines by the developers (Bernstein, Burles, & Prochaska, 2015; Bochanski et al., 2009). The reduction procedure -- including a complete list of the input parameters and available functionality -- is provided as online documentation hosted by Read the Docs, which is regularly updated. (https://pypeit.readthedocs.io/en/latest/). Release v1.0.3 serves the following spectrographs: Gemini/GNIRS, Gemini/GMOS, Gemini/FLAMINGOS 2, Lick/Kast, Magellan/MagE, Magellan/Fire, MDM/OSMOS, Keck/DEIMOS (600ZD, 830G, 1200G), Keck/LRIS, Keck/MOSFIRE (J and Y gratings tested), Keck/NIRES, Keck/NIRSPEC (low-dispersion), LBT/Luci-I, Luci-II, LBT/MODS (beta), NOT/ALFOSC (grism4), VLT/X-Shooter (VIS, NIR), VLT/FORS2 (300I, 300V), WHT/ISIS.
Summary
PypeIt is a configurable, semi-automated pipeline that reduces raw spectroscopic images into calibrated one- and two-dimensional spectra across many optical and near-infrared instruments. Its workflow automatically classifies inputs, applies calibration and extraction algorithms, and provides documented, quality-assured outputs, while requiring suitable calibration frames and continued instrument expansion.
- Scope and accessibility: Release v1.0.3 supports a broad range of Gemini, Lick, Magellan, Keck, LBT, NOT, VLT, and WHT spectrographs.Supported configurations include multiple gratings, detectors, and observing modes, with some instruments marked beta or limited to tested setups.
- Scope and accessibility: The release is intended for both experienced spectroscopists and users without prior reduction experience and is designed for longslit, multislit, and cross-dispersed echelle spectra.The authors plan to expand support to additional ground-based optical and near-infrared spectrographs with community involvement.
- Requirements and scope: Successful reduction requires recommended calibration data, including flats and arcs matched to the science setup, while near-infrared wavelength calibration uses sky lines instead of arcs.Additional optional frames include bias or dark frames, twilight sky frames, pixel flats, and standard-star frames depending on the science goal and instrument.
- Automated workflow: PypeIt automatically characterizes raw frames from header information and can use SPIT pixel-data classification to generate an editable reduction input file.Users can manually update the classification of input raw images before reduction.
- Automated workflow: The pipeline applies overscan, optional bias and dark corrections, bad-pixel masking, robust master-calibration construction, slit tracing, wavelength calibration, flat modeling, and flexure measurement.Wavelength calibration can use master arcs or near-infrared science data, with a graphical interface available when automated calibration fails.
- Extraction and sky subtraction: PypeIt jointly extracts objects and models the sky with a two-dimensional, tilt-aware b-spline procedure that is locally refined around the science target.The sky-subtraction algorithm is reported to achieve the Poisson limit before boxcar and optimal extraction produce one-dimensional spectra.
- Outputs and usability: The pipeline produces fully reduced one- and two-dimensional spectra, with optional flux calibration, exposure combination, telluric correction, calibration products, plots, and documented FITS data models.The two-dimensional outputs retain spatial information, and the software includes automatically generated plots for quality-assurance inspection.