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KODIAQ Overview

The Keck Observatory Database of Ionized Absorption toward Quasars (KODIAQ) is a repository of reduced, continuum normalized quasar spectra derived from public HIRES raw data and flux calibrated quasar spectra derived from public ESI raw data served through the Keck Observatory Archive (KOA). Data are provided in one dimensional flux and error fits files. Intermediate data extraction products are also available. The data are summarized in O'Meara et al 2020, O'Meara et al. 2017, AJ in press, arXiv:1707.07905, O'Meara et al. 2015, AJ, 150, 111, and Lehner et al. 2014, ApJ 788, 119. KODIAQ was funded through NASA ADAP grants NNX10AE84G and NNX16AF52G.

All HIRES data in KODIAQ (DR1 and DR2) are taken in raw form from the KOA and organized by observing run, where an observing run is a group of nights with a single PI and a single HIRES cross-disperser configuration. The data for the observing run are then processed together using the HIRedux (http://www.ucolick.org/~xavier/HIRedux) suite of tools in IDL developed by J. X. Prochaska at UCSC. Data are organized within each observing run by setups. Each setup contains data having the same HIRES decker, binning, echelle angle and cross disperser angle (within a tolerance of 4 encoder steps for the latter value). Upon completion of the HIRedux pipeline steps, all data for an individual quasar in a setup are coadded (weighted by signal to noise.) An order-by-order continuum fit is manually preformed using a high order Legendre polynomial. The echelle orders are then combined (again weighting by signal to noise) to produce 1D flux and error fits files (_f.fits and _e.fits, respectively). Finally, the files are placed in the KOA, after being renamed with their KODIAQ QSO ID.

KODIAQ at the KOA provides access to these 1D files. In addition, users can download the tarball for the entire observing run from which a KODIAQ quasar was observed to facilitate a user's ability to perform a different extraction, wavelength solution, or continuum fit. Familiarity with HIRedux is strongly encouraged so that users can best make use of these tarballs.

All KODIAQ data are provided to the community freely and without warranty. We request that any published use of KODIAQ data use both the KOA and KODIAQ acknowledgements in the footer of this page, including acknowledgment of the original Keck program PIs for any of the data.

Users of KODIAQ data with questions about the data reduction are strongly encouraged to first read O'Meara et al. 2015, AJ, 150, 111 and then download and install the HIRedux routines and familiarize themselves with their use.