eBOSS ELG target selection
|EPFL, Lausanne, Swizterland|
|MPE/MPG, Munich, Germany|
ELGs are selected to cover the redshift range 0.7 < z < 1.1. The DECaLS photometry was used to draw the targets for spectroscopic observations.
In DR15 we released only the targets for the SGC. Targets for the NGC and all redshifts are available in DR16 and later releases.
The DECam Legacy Survey (DECaLS; co-P.I.s: A.Dey and D.J.Schlegel) is an on-going imaging survey covering 6700 deg2 of the extragalactic sky that lies in the region -20° < Dec. < +30° to depths of g=24.7, r=23.9, and z=23.0 mag (5σ point-source).
In addition, the DECaLS program also processes any public DECam observations in the DESI footprint, the largest component being the DES survey.
The DECaLS data and processing pipeline are public, with a release every six months. The footprint of the eBOSS ELG program is shown in Figure 1.
The target selection algorithm is completely described in the Table 1 below. Objects for the SGC are identified in the
EBOSS_TARGET1 bitmask under bit 43, corresponding to the name ELG1_SGC. Objects for the NGC are found in the same mask under bit 44, with the name ELG1_NGC.
A representation of how the ELG sample is positioned compared to other cosmological samples is shown in Figure 2.
The catalogs of targets in the SGC is released as a value-added catalog within the SDSS DR14.
The software to select the ELGs from the DECaLS catalogs is available here through the svn.
The software to measure emission line and add redshift quality flags to the ELGs is available through here via the svn.