Spectral cube extraction for the VLT/SPHERE IFS: Open-source pipeline with full forward modeling and improved sensitivity
arXiv:2210.06390 · doi:10.1051/0004-6361/202244587
Abstract
We present a new open-source data-reduction pipeline to reconstruct spectral data cubes from raw SPHERE integral-field spectrograph (IFS) data. The pipeline is written in Python and based on the pipeline that was developed for the CHARIS IFS. It introduces several improvements to SPHERE data analysis that ultimately produce significant improvements in postprocessing sensitivity. We first used new data to measure SPHERE lenslet point spread functions (PSFs) at the four laser calibration wavelengths. These lenslet PSFs enabled us to forward-model SPHERE data, to extract spectra using a least-squares fit, and to remove spectral crosstalk using the measured lenslet PSFs. Our approach also reduces the number of required interpolations, both spectral and spatial, and can preserve the original hexagonal lenslet geometry in the SPHERE IFS. In the case of least-squares extraction, no interpolation of the data is performed. We demonstrate this new pipeline on the directly imaged exoplanet 51 Eri b and on observations of the hot white dwarf companion to HD 2133. The extracted spectrum of HD 2133B matches theoretical models, demonstrating spectrophotometric calibration that is good to a few percent. Postprocessing on two 51 Eri b data sets demonstrates a median improvement in sensitivity of 80% and 30% for the 2015 and 2017 data, respectively, compared to the use of cubes reconstructed by the SPHERE Data Center. The largest improvements are seen for poorer observing conditions. The new SPHERE pipeline takes less than three minutes to produce a data cube on a modern laptop, making it practical to reprocess all SPHERE IFS data.
17 pages, 11 figures. Software available at: https://github.com/PrincetonUniversity/charis-dep
References in corpus (13)
- The Gemini Planet Imager: First Light
- Discovery of a warm, dusty giant planet around HIP65426
- Performance of the VLT Planet Finder SPHERE II. Data analysis and Results for IFS in laboratory
- Near-infrared scattered light properties of the HR4796A dust ring: a measured scattering phase function from 13.6deg to 166.6deg
- Discovery of a low-mass companion inside the debris ring surrounding the F5V star HD206893
- The Young Suns Exoplanet Survey: Detection of a wide orbit planetary mass companion to a solar-type Sco-Cen member
- Spectral and orbital characterisation of the directly imaged giant planet HIP 65426 b
- TRAP: A temporal systematics model for improved direct detection of exoplanets at small angular separations
- BEAST begins: Sample characteristics and survey performance of the B-star Exoplanet Abundance Study
- A dusty benchmark brown dwarf near the ice line of HD 72946
- Shape model of asteroid (130) Elektra from optical photometry and disk-resolved images from VLT/SPHERE and Nirc2/Keck
- A grid of Synthetic Spectra for Hot DA White Dwarfs and Its Application in Stellar Population Synthesis
- RSM detection map for direct exoplanet detection in ADI sequences