BGS SV TS paper

[changhoonhahn]

Year1 KP1 supporting paper wiki, sv workshop doc that provides:

• science motivation for BGS
• motivation for extended SV selection and performance of extended SV selection
• target selection and expected number densities for main sample
• sensitivity to spurious signal

Also:

• Present astrophysics of the tracer and use as probe of physics
• Present scope of DESI’s plan for tracer
• Present challenges (decision trees) and goals in constraining physics
• Present full SV selection and motivation
• Present results in context of science requirements
• Present additional information, including systematics and projections for survey

[changhoonhahn]

Outline of the paper from SV workshop (see also [SV workshop google doc])

1. Intro
   • Background of tracer as used in large spectroscopic surveys (how it was used in the past) SDSS main galaxy sample
   • DESI overview
   • Boilerplate cross-reference between TS papers
   • Motivation to use tracer for DESI, including potential scope over full footprint, why is number density chosen
2. Science Req.
   • Scientific goals of sample (e.g. BAO precision for BGS BRIGHT) what about for BGS faint?
   • Req. on the sample to reach those goals
   • What challenge in using target class to meet those requirements (decision tree)?
   • additional challenges (completeness and uniformity)
3. Properties of tracer in imaging data, properties of imaging data
   • spectroscopic features, broadband SED, and/or morphology that make tracer distinct in imaging data (example spectrum, scatter plot of known targets on color-color distribution)
   • how much overlap/contamination with other astrophysical sources
   • what imaging data do we have to make the TS (WISE/grz/Gaia) and what does that enable for TS? color cuts, star-galaxy separation
4. TS for SV combine with 3
   • Assumptions of n(z)/color cuts informed by prior experience GAMA overlap
   • extended selection of targets from imaging data, why are we extending the boundaries?
   • assessment of uniformity for various selections, regression on imaging properties, zeropoints (identify largest sources of spurious signal)
   • application to TS and fiber assignment, brief discussion with references to relevant supporting paper
   • code in desi_target to make skymaps, QA plots, that would offer consistent figures and code
5. Results from SV
   • Take catalog redshift at face value and focus on n(z) and redshift completeness. The redshift failures will be discussed in the pipeline papers. Cite thresholds that determine truth in the assessment of catalog, but point to other paper
   • determination of n(z), spectroscopic completeness as a function of color, magnitude, and other selection criteria
   • answer other decision tree question using SV data
   • state final selection algorithm
6. Implications for five-year DESI program
7. Conclusion

[changhoonhahn]

overleaf of DESI BGS SV target selection paper: https://www.overleaf.com/1236443545pnmrcnbcspwp