APOGEE-2 SRD Mini-Review December 5, 2013 APOGEE-2 SRD Data and Pipeline Requirements Jon Holtzman New Mexico State

December 5, 2013 Data and software requirements (Sections 6 & 7) Data/instrument/software requirements RV precision Elemental abundances Elemental abundance precision and accuracy Sample size Spectral resolution, coverage, sampling S/N Data reduction pipeline ASPCAP pipeline Bottom line: APOGEE-2 wants to extend APOGEE-1 seamlessly, and APOGEE-S wants to blend with APOGEE-N seamlessly, so overall instrument/software performance/requirements should mostly stay the same Sample size and S/N are more closely tied to target/field selection

December 5, 2013 RV Requirements Current precision 100 m/s for S/N=60 exceeds APOGEE requirements (300 m/s for S/N=100) None of the science goals so far discussed require better precision, so APOGEE requirement retained going into APOGEE-2 Higher RV precision appears to be feasible and offers “opportunity science” Not requirement, but goal? Note fiber Fabry-Perot (FFP) possibilities

December 5, 2013 Elemental Abundances Original APOGEE abundance suite Top priority: C, N, O, Mg, Al, Si, Ca, Fe, Ni Medium: Na, S, Ti, Mn, K Lower: V, Cr, O White papers do not generally call for individual element abundances specifically This is a key capability of the instrument Motivation probably needs to be included in SRD! Requirements may be a bit trickier, since it really is new terrain at some level

December 5, 2013 Abundance Precision and Accuracy APOGEE requirement: dex precision dex accuracy - For all top-priority elements, across all stellar types Unachievable in some regions of parameter space Currently still being worked on for APOGEE-1! Overly strict for some science cases May need to be re-formulated

December 5, 2013 Spectral resolution, coverage, sampling Based on WPs and compatibility arguments, original APOGEE requirements on resolution, coverage, and sampling retained

December 5, 2013 Reduction pipelines Pipelines currently functioning and delivering science-worthy products Significant improvements still certainly possible Reduction pipeline: telluric correction, sky subtraction, RV precision ASPCAP No major changes forseen for APOGEE-2 Do need to keep track of different sources of data Would like to develop alternative abundance pipeline, but path to this not clearly identified

December 5, 2013 Sample size We’re a bit gun-shy about putting number of stars as a requirement Did not serve us well with APOGEE-1: certainly need to consider distribution across Galactic components Rigorous scientific justification for an absolute number is challenging Numbers from WGs may need to be refined (e.g., bulge and disk strategies), and programs need to be merged (e.g., bulge + disk) Clearly do want to motivate sample sizes with scientific arguments Need to define truly minimal survey requirements for core programs

December 5, 2013 S/N requirements Current requirements are S/N=100 per “Nyquist sampled pixel” ASPCAP tests/results on stellar parameters suggest issues (e.g., “noding”) at S/N<70 S/N >100 was originally motivated by crude simulations for individual element abundances, but these do not provide a “hard line” because requirements depend on metallicity and temperature S/N>100 is a “standard traditional” requirement for high- resolution spectral abundance analysis Obviously, an important item: discussion? Do want continuity with APOGEE-1 Super-persistence is discussed in S/N section in draft, but is really a separate issue: it is a key issue if targetting depends on fainter stars (i.e., medium and long cohorts)