1. 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

2. APOGEE: “The Big Picture”
Galactic Cartography
Part of SDSS III & IV
R=22,400 NIR H-band (λ μm) 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

3. 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

4. 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

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

6. 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

7. 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 !!

8. Detection of Ce II Lines in α Boo
Cunha et al 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

9. 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

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

11. 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

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

13. 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

14. 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

15. 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

16. 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

17. Test Slide
Test text