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arXiv · 2007.14484

Validation of Emission-Line Galaxies Target Selection Algorithms for the Dark Energy Spectroscopic Instrument Using the MMT Binospec

Tanveer Karim·Jae H. Lee·Daniel J. Eisenstein·Etienne Burtin·John Moustakas·Anand Raichoor·Christophe Yèche
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Abstract

The forthcoming Dark Energy Spectroscopic Instrument (DESI) experiment plans to measure the effects of dark energy on the expansion of the Universe and create a $3$D map of the Universe using galaxies up to $z \sim 1.6$ and QSOs up to $z \sim 3.5$. In order to create this map, DESI will obtain spectroscopic redshifts of over $30$ million objects; among them, a majority are \oii emitting star-forming galaxies known as emission-line galaxies (ELGs). These ELG targets will be pre-selected by drawing a selection region on the $g - r$ vs. $r - z$ colour-colour plot, where high redshift ELGs form a separate locus from the lower redshift ELGs and interlopers. In this paper, we study the efficiency of three ELG target selection algorithms -- the final design report (FDR) cut based on the DEEP2 photometry, Number Density Modelling and Random Forest -- to determine how the combination of these three algorithms can be best used to yield a simple selection boundary that will be best suited to meet DESI's science goals. To do this, we selected $17$ small patches in the DESI footprint where we run the three target selection algorithms to pre-select ELGs based on their photometry. We observed the pre-selected ELGs using the MMT Binospec, which is similar in functionality to the DESI instrument, to obtain their spectroscopic redshifts and fluxes of $1054$ ELGs. By analysing the redshift and fluxing distribution of these galaxies, we find that although NDM performed the best, simple changes in the FDR definition would also yield sufficient performance.

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Tanveer Karim, Jae H. Lee, Daniel J. Eisenstein, Etienne Burtin, John Moustakas, Anand Raichoor, Christophe Yèche. 2020-07-28. Validation of Emission-Line Galaxies Target Selection Algorithms for the Dark Energy Spectroscopic Instrument Using the MMT Binospec. https://doi.org/10.1093/mnras%2Fstaa2270

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