Holistic spectroscopy: complete reconstruction of a wide-field, multiobject spectroscopic image using a photonic comb

Kos, Janez and Bland-Hawthorn, Joss and Betters, Christopher H. and Leon-Saval, Sergio and Asplund, Martin and Buder, Sven and Casey, Andrew R. and D'Orazi, Valentina and de Silva, Gayandhi and Freeman, Ken and Lewis, Geraint and Lin, Jane and Martell, Sarah L. and Schlesinger, Katharine and Sharma, Sanjib and Simpson, Jeffrey D. and Zucker, Daniel and Zwitter, Tomaz and Hayden, Michael and Horner, Jonathan and Nataf, David M. and Ting, Yuan-Sen (2018) Holistic spectroscopy: complete reconstruction of a wide-field, multiobject spectroscopic image using a photonic comb. Monthly Notices of the Royal Astronomical Society, 480 (4). pp. 5475-5494. ISSN 0035-8711

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The primary goal of Galactic archaeology is to learn about the origin of the Milky Way from the detailed chemistry and kinematics of millions of stars. Wide-field multifibre spectrographs are increasingly used to obtain spectral information for huge samples of stars. Some surveys (e.g. GALAH) are attempting to measure up to 30 separate elements per star. Stellar abundance spectroscopy is a subtle art that requires a very high degree of spectral uniformity across each of the fibres. However, wide-field spectrographs are notoriously non-uniform due to the fast output optics necessary to image many fibre outputs on to the detector. We show that precise spectroscopy is possible with such instruments across all fibres by employing a photonic comb - a device that produces uniformly spaced spots of light on the CCD to precisely map complex aberrations. Aberrations are parametrized by a set of orthogonal moments with ̃100 independent parameters. We then reproduce the observed image by convolving high-resolution spectral templates with measured aberrations as opposed to extracting the spectra from the observed image. Such a forward modelling approach also trivializes some spectroscopic reduction problems like fibre cross-talk, and reliably extracts spectra with a resolution ̃2.3 times above the nominal resolution of the instrument. Our rigorous treatment of optical aberrations also encourages a less conservative spectrograph design in the future.

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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Published version deposited in accordance with the copyright policy of the publisher.
Faculty/School / Institute/Centre: Current - Faculty of Health, Engineering and Sciences - School of Agricultural, Computational and Environmental Sciences
Date Deposited: 15 Feb 2019 00:13
Last Modified: 22 Feb 2019 01:28
Uncontrolled Keywords: instrumentation; spectrographs; data analysis; image processing; spectroscopic; abundances; instrumentation and methods for astrophysics; astrophysics; solar and stellar astrophysics
Fields of Research : 02 Physical Sciences > 0201 Astronomical and Space Sciences > 020110 Stellar Astronomy and Planetary Systems
Identification Number or DOI: 10.1093/mnras/sty2175
URI: http://eprints.usq.edu.au/id/eprint/35794

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