Issue |
A&A
Volume 655, November 2021
|
|
---|---|---|
Article Number | A53 | |
Number of page(s) | 19 | |
Section | Numerical methods and codes | |
DOI | https://doi.org/10.1051/0004-6361/202141392 | |
Published online | 17 November 2021 |
Spectral shape corrections for SDSS BOSS quasars
1
INAF, Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy
e-mail: dinko.milakovic@inaf.it
2
Clare Hall, University of Cambridge, Herschel Road, Cambridge CB3 9AL, UK
3
AdServer Ltd, 37 Professora Popova Street, Saint-Petersburg 197022, Russia
Received:
26
May
2021
Accepted:
9
August
2021
Modifications were made to the Sloan Digital Sky Survey’s Baryonic Oscillations Spectroscopic Survey (SDSS/BOSS) optical fibres assigned to quasar targets in order to improve the signal-to-noise ratio in the Ly-α forest. However, the consequence of these modifications is that quasars observed in this way require additional flux correction procedures in order to recover the correct spectral shapes. In this paper we describe such a procedure, based on the geometry of the problem, and other observational parameters. Applying several correction methods to four SDSS quasars with multiple observations permits a detailed verification of the relative performances of the different flux correction procedures. We contrast our method (which takes into account a wavelength-dependent seeing profile) with the BOSS pipeline approach (which does not). Our results provide independent confirmation that the geometric approach employed in the SDSS pipeline works well, although with room for improvement. By separating the contributions from four effects, we are able to quantify their relative importance. Most importantly, we demonstrate that wavelength dependence has a significant impact on the derived spectral shapes and thus should not be ignored.
Key words: instrumentation: spectrographs / cosmology: observations / quasars: absorption lines / intergalactic medium / surveys / techniques: spectroscopic
© ESO 2021
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