Optimal Techniques in Two‐dimensional Spectroscopy: Background Subtraction for the 21st Century

By D. Kelson. 2003

554 citations recorded by the source corpus.

In two‐dimensional spectrographs, the optical distortions in the spatial and dispersion directions produce variations in the subpixel sampling of the background spectrum. Using knowledge of the camera distortions and the curvature of the spectral features, one can recover information regarding the background spectrum on wavelength scales much smaller than a pixel. As a result, one can propagate this better sampled background spectrum through inverses of the distortion and rectification transformations and accurately model the background spectrum in two‐dimensional spectra for which the distortions have not been removed (i.e., the data have not been rebinned/rectified). The procedure, as outlined in this paper, is extremely insensitive to cosmic rays, hot pixels, etc. Because of this insensitivity to discrepant pixels, sky modeling and subtraction need not be performed as one of the later steps in a reduction pipeline. Sky subtraction can now be performed as one of the earliest tasks, perhaps just after dividing by a flat field. Because subtraction of the background can be performed without having to “clean” cosmic rays, such bad pixel values can be trivially identified after removal of the two‐dimensional sky background.

Subfields: Astronomy and Astrophysics, Global and Planetary Change, Instrumentation

View Paper: https://www.semanticscholar.org/paper/5109a6d8bbc9d66953afea8f305c1b611cad5be0

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

In Global and Planetary Change

In Instrumentation

Citations in the corpus

The Transiting Extrasolar Giant Planet around the Star OGLE-TR-113 (2004, methodology): “The spectra were reduced using standard tasks in IRAF1, as well as rectification tools developed by Kelson (2003).”
DISCOVERIES FROM A NEAR-INFRARED PROPER MOTION SURVEY USING MULTI-EPOCH TWO MICRON ALL-SKY SURVEY DATA (2010, methodology): “The pipeline employs simultaneous B-spline fitting (Kelson 2003) to both the background and object to measure the spectrum.”
STRONG NEBULAR LINE RATIOS IN THE SPECTRA of z ∼ 2–3 STAR FORMING GALAXIES: FIRST RESULTS FROM KBSS-MOSFIRE (2014, methodology): “D b-spline model to the background residuals only, using a method similar to that described by Kelson (2003).”
LoCuSS: first results from strong-lensing analysis of 20 massive galaxy clusters at z= 0.2 (2009, methodology): “The data were reduced using the Python version of the Kelson (2003) reduction scripts, which offer the advantage of processing the images in their distorted framework.”
A SEARCH FOR STARS OF VERY LOW METAL ABUNDANCE. VI. DETAILED ABUNDANCES OF 313 METAL-POOR STARS (2014, methodology): “′′0 slit, data reduction, extraction, and wavelength calibration were performed using the MIKE data reduction pipeline written by D. Kelson (see also Kelson 2003).”
The Evolution of Optical Depth in the Lyα Forest: Evidence Against Reionization at z~6 (2006, unknown): “The IDL package is based on the optimal sky subtraction technique of Kelson (2003).”
Iron Emission in the z = 6.4 Quasar SDSS J114816.64+525150.3 (2003, methodology): “The spectra were extracted from bias-subtracted, flattened 2- dimensional frames using an optimal weighting algorithm, and using the sky-subtraction code of Kelson (2003).”
Ultraviolet emission lines in young low-mass galaxies at z ≃ 2: physical properties and implications for studies at z > 7 (2014, methodology): “The individual exposures were rectified, cleaned of cosmic rays and stacked using the pipeline of Kelson (2003).”
DISCOVERY OF THREE z > 6.5 QUASARS IN THE VISTA KILO-DEGREE INFRARED GALAXY (VIKING) SURVEY (2013, methodology): “The pipeline produces an order-by-order two-dimensional spectral model of the sky using the principles outlined in Kelson (2003) and subtracts this from the flattened data frames.”
Berkeley Supernova Ia Program – I. Observations, data reduction and spectroscopic sample of 582 low-redshift Type Ia supernovae (2012, methodology): “For this spectrum, the sky was subtracted from the images using the method described by Kelson (2003).”
Discovery of extreme [O III] λ5007 Å outflows in high-redshift red quasars (2015, methodology): “It is based on the techniques of Kelson (2003) with all the steps computed on the unrectified two-dimensional frames.”
The Initial-Final Mass Relation: Direct Constraints at the Low-Mass End (2007, methodology): “Specifically, we used Python routines that are described in Kelson et al. (2000) and Kelson (2003) to perform bias subtraction, vertical distortion corrections, wavelength calibration (typical rms scatter in the dispersion solutions is <0.05 Å), flat-field corrections, and sky subtraction.”
A STELLAR CENSUS OF THE TUCANA–HOROLOGIUM MOVING GROUP (2014, methodology): “We reduced the raw spectra using the CarPy pipeline (Kelson 2003)7 but used observations of spectrophotometric standard stars to measure and flatten the blaze function due to the uncertain temperature of the flat lamp.”
One Percent Determination of the Primordial Deuterium Abundance (2017, methodology): “We employed an optimal sky subtraction and object extraction technique (Kelson 2003), and each pixel was assigned a wavelength using an exposure of a ThAr lamp that bracketed each science exposure.”
A Population of Faint Extended Line Emitters and the Host Galaxies of Optically Thick QSO Absorption Systems (2007, methodology): “The sky was then subtracted from each exposure using an optimal sky-subtraction technique based on Kelson (2003), whereby the sky counts aremodeled as a function of wavelength and slit position without rectifying the original data.”
PypeIt: The Python Spectroscopic Data Reduction Pipeline (2020, methodology): “PypeI t jointly performs the object extraction and b-spline (Kelson, 2003) sky subtraction.”
A Keck Survey for Gravitationally Lensed Lyα Emitters in the Redshift Range 8.5 < z < 10.4: New Constraints on the Contribution of Low-Luminosity Sources to Cosmic Reionization (2007, methodology): “Following techniques described in Kelson (2003), the two-dimensional spectra were not straightened prior to sky subtraction, thus ensuring sub-pixel sampling of atmospheric emission lines which, in turn, led to a significantly improved removal of the sky background.”