Adding the s-Process to APOGEE Stellar Populations: - Evolving the Line List - Pushing to the M-dwarfs Verne V. Smith (NOAO) Katia Cunha, Matthew Shetrone, Sten Hasselquist, Diogo Souto, Szabolcs Meszaros, Jon Holtzman + APOGEE/ASPCAP Team Photo by S. Majewski

APOGEE: “The Big Picture” Galactic Cartography Part of SDSS III & IV R=22,400 NIR H-band (λ1.52-1.69μm) 300-fibers Kinematic (~100 m/s) Chemical (~0.1 dex) ~15 elements per star  f(Teff, log g, [m/H]) 140,000 stars in DR12 500,000 stars by 2020 APOGEE-1 (2011 – 2014) APOGEE-2 will add Data Release 13 (DR13) Majewski et al. 2017

Elemental Abundances λ1.51 – 1.69μm Already in, but may need work Also lines in current list from Ge I and Y II, but very weak. Some doubly ionized lines ( Ce III) but not visible in red giants λ1.51 – 1.69μm C, N, O determined (mostly) from molecular transitions: CO, OH, CN Everything else atomic lines, almost all neutral. Ti II Note lack of heavy elements (Z>30) Stellar parameters and chemical abundances all hang on the APOGEE line list

Test Slide Plus Kurucz compilations & molecules Continuing to improve on identifying missing lines from the most recent line lists; can add additional elements from these previously unknown lines

Expanding the APOGEE Periodic Table Focus on the heavy elements Already in, but may need work Hasselquist et al. (2016) Cunha et al. (2017)

Focus on the s-Process: Vetting the Lines Identify candidate lines based on atomic properties In general, for heavy-element H-band lines, no laboratory gf-values Use combination of α Boo and the Sun to derive gf-values: “astrophysical gf-values” Also use chemically peculiar stars in APOGEE as tests Important Analysis that is self-consistent with ASPCAP Hasselquist et al. (2016) 10 Nd II lines Required s-process rich stars to calibrate Cunha et al. (2017) – in preparation 9 Ce II lines (1 falls in APOGEE chip gap) all visible in α Boo Rests on optical analysis Ce II – gf-values from Lawler et al. (2009) For Ce II, estimated internal scatter ~+/-0.05 dex Adding the s-process as a rigorously determined quantity to APOGEE

Nd II from Hasselquist et al. 2016 2016, ApJ, 833, 81 10 Nd II lines identified in APOGEE window Useful in tracking Sgr streams Ce II !!

Detection of Ce II Lines in α Boo Cunha et al. 2017-about to be submitted 9 lines in APOGEE window (1 in gap) gf-values from α Boo using optical A(Ce) from Ce II lines – Lawler et al. (2009) gf-values ~not detectable in Sun—but constraints on blending atomic lines

Ce II in APOGEE Spectra: NGC6819 ~1-2 Gyr old cluster ~solar metallicity Red giant near RC – Teff~4700K Ce II easily measurable Kepler cluster

Ce II in an APOGEE Metal-Poor Giant [Fe/H]~ -1.0 Teff~4000K Ce II easy to measure

Tests of Ce II Lines in APOGEE Window Cunha et al. (2017) APOGEE Ce II lines with astrophysical gf-values agrees with optical results Ce II lines detectable in large fraction of the APOGEE red giants With Ce II & Nd II the ability to probe the s-process across the Galaxy Note s-process rich, N-rich, Al-rich star: Cunha et al. (2017) found Ce enhancement. Noted earlier by Fernandez-Trincado (2017) as N- & Al-rich, retrograde orbit, suggested to be possible ω Cen escapee. Part of sample identified by Schiavon et al. (2017) in the inner Galaxy

Detection and Uncertainties of Ce II Lines Measurable in vast majority of APOGEE red giants

Modifying the APOGEE Line List to Include M-dwarfs: Souto Ph.D. Thesis Souto + Cunha Serendipitous observations in APOGEE-1 Ancillary science program: Kepler H-band region ~clean in even cool M-dwarfs Added H2O from Barber et al. (2006)-26M lines in APOGEE window: fits well FeH : Hargreaves et al. (2012) – needs work. Stronger features fit well Kepler 138

Example of an M-dwarf Fit in Kepler 138 Teff~3800K Isolate influence of H2O and FeH Can derive 13 elemental abundances Testing line list and models down to Teff=2800K so far New diagnostics: OH, H2O; Fe I / FeH

Push the Envelope Cooler M-dwarfs Test the line list and ability to model 1D, LTE Different model famililes: e.g., MARCS, BT-settl No weather Teff=3200K Teff=2800K

Summary: APOGEE Line List and Analysis is a Work in Progress Nd II and Ce II are being added Rb I is there - not clear yet how well ASPOGEE/ASPCAP can do. Always the optimist Other lines are in there – maybe 1st-peak – Zr I (?), certainly other 2nd peak – stay tuned. r-process search In addition - line list will continue to be improved: more complete lists, better atomic data, in particular f-values, more molecules as needed Addition of H2O and FeH to include M-dwarfs Cooler giants

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