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Preliminary Target Selection for the DESI Quasar (QSO) Sample

Christophe Yèche, Nathalie Palanque-Delabrouille, Charles-Antoine Claveau, David D. Brooks, Edmond Chaussidon, Tamara M. Davis, Kyle S. Dawson, Arjun Dey, Yutong Duan, Sarah Eftekharzadeh, Daniel J. Eisenstein, Enrique Gaztañaga, Robert Kehoe, Martin Landriau, Dustin Lang, Michael E. Levi, Aaron M. Meisner, Adam D. Myers, Jeffrey A. Newman, Claire Poppett, Francisco Prada, Anand Raichoor, David J. Schlegel, Michael Schubnell, Ryan Staten, Gregory Tarlé, Rongpu Zhou

Abstract

The DESI survey will measure large-scale structure using quasars as direct tracers of dark matter in the redshift range $0.9<z<2.1$ and using quasar Ly-$α$ forests at $z>2.1$. We present two methods to select candidate quasars for DESI based on imaging in three optical ($g, r, z$) and two infrared ($W1, W2$) bands. The first method uses traditional color cuts and the second utilizes a machine-learning algorithm.

Preliminary Target Selection for the DESI Quasar (QSO) Sample

Abstract

The DESI survey will measure large-scale structure using quasars as direct tracers of dark matter in the redshift range and using quasar Ly- forests at . We present two methods to select candidate quasars for DESI based on imaging in three optical () and two infrared () bands. The first method uses traditional color cuts and the second utilizes a machine-learning algorithm.

Paper Structure

This paper contains 3 sections, 1 figure.

Table of Contents

  1. Introduction
  2. Quasar Target Selection
  3. Conclusion

Figures (1)

  • Figure 1: Left: Colors in the optical ($grz$ is a linear combination of $g$,$r$ and $z$) or near-infrared (W is a linear combination of W1 and W2) of objects photometrically classified as stars (red) or spectroscopically classified as QSOs (blue and black contours). The green circles show targets selected by the RF. The black line illustrates the "infrared excess" color cut (sources below this line are rejected in the color-cut selection). Right: Expected distribution of QSO redshifts from the color-cut (blue) or RF (red) selections, compared to the QSO luminosity function to $r<22.7\,(AB)$ (green). The filled circles show observations obtained during DESI commissioning.