APOGEE APACHE POINT OBSERVATORY GALACTIC EVOLUTION EXPERIMENT Jennifer Johnson Ohio State University
APOGEE AT A GLANCE SDSS-III survey PI: Steve Majewski (UVa) High-resolution H-band survey (15 elements) R~28,000, spectra on 3 chips, 300 fibers 10 5 Galactic stars (mostly red giants) H < 12.5 (usually) S/N~100 per res. element relative abundance error=0.1 dex May 2011-June 2014 Observations in highly reddened regions All Galactic populations: disk, halo & bulge Instrument design set, but field and target selection and software discussions active
KEY APOGEE PERSONEL Contributed Effort (NB: Incomplete list -- many have contributed expertise and SDSS heritage to APOGEE science,hardware, software development) Software:Ricardo Schiavon (Survey Sci.), Jon Holtzman (Reduction S/W), Carlos Allende-Prieto (ASPCAP S/W), Dmitry Bizyaev, Matt Shetrone Lab Data: Matt Shetrone, Jim Lawler, Ricardo Schiavon, Dmitry Bizyaev, Carlos Allende-Prieto,Verne Smith Field and Target Selection: J. Johnson, P. Frinchaboy, Gail Zasowski, L. Girardi, H. Rocha-Pinto, Annie Robin, J. Munn, Joleen Carlberg Early APOGEE Definition - Science: Katia Cunha, Jim Gunn, Remy Indebetouw, Dmitry Bizyaev, Robert O Connell, Neill Reid, Verne Smith, Kathryn Johnston, Jeffrey Munn, Matt Shetrone, David Spergel APOGEE Hardware Definition: Robert Barkhouser, Jeff Crane, Daniel Eisenstein, Jim Gunn, Jarron Leisenring, Steve Smee Infrastructure and Data: French Leger, Larry Carey, Nick McDonald, Russell Owens, Craig Loomis, Mike Blanton 3
Hardware Development: Current Status VPH being fab d (ETA early-may) Camera being assembled (ETA late- April) Detector Assembly being fab d (ETA early-june) Fiber prototypes being tested, production order soon (ETA Summer) 4 Collimator being fit-up, coated (ETA late-april) Slithead design being reviewed (ETA early May) Fold 2 being coated (ETA mid- April) Cryostat being cold vacuum tested (ETA late- April) Fold 1 awaiting coating (ETA late-april)
APOGEE AND CHEMICAL EVOLUTION Disk Bulge Halo
WHERE DO THE ELEMENTS COME FROM?
THE APOGEE PERIODIC TABLE
DISK AND BULGE CHEMICAL EVOLUTION Ejecta from Type Ia supernova and AGB stars Ejecta from metal-rich supernovae and AGB stars Odd-Z elements Cu and Zn S-process C vs. N Different star formation histories Bulge very rapid (at least majority) Disk rate varies as a function of R G Ties into formation of Galaxy as a whole See how we got to today
COMPARING BULGE AND DISKS Alves-Brito et al. 2010
COMPARING BULGE AND DISKS Alves-Brito et al. 2010
BETTER MORE ELEMENTS = Epstein et al. 2010
ABUNDANCE GRADIENTS IN THE DISK Jacobson et al. 2009
CURRENT SAMPLES/SURVEYS Largest samples of thin/thick disk stars with highres abundances 1000 stars Largest samples of bulge stars with high-res abundances 800 stars APOGEE ~ 10 5 stars Very complimentary to Geneva-Copenhagen, SEGUE, LAMOST, RAVE, GAIA, HERMES More luminous, redder stars Regions of high reddening Infrared spectra (test of stellar atmospheres/transitions)
TARGET SELECTION Selection based on 2MASS catalog Aim for red giants: H-band spectra have lines Most luminous tracers 80% observed stars should be giants 14 Color cut: (J-K) 0 > 0.5 Advantage: unbiased Disadvantage: unbiased Reddening corrections from JHK and IRAC colors 10 Gyr Padua isochrones in 2MASS colors These discussions currently underway
Current Field Selection Plan 15
CURRENT FIELD SELECTION PLAN: CLOSE-UP ON THE DISK & BULGE FIELDS 29 targeted star clusters for calibration (globular and open) ~220 completely in field of view ~30 partially in field of view 16
ANTICIPATED SPATIAL DISTRIBUTION For currently selected fields (not all fields selected yet): Thin disk 77800 stars Bulge 9000 stars Thick disk 5600 stars Halo 2900 stars 17
ANTICIPATED SPATIAL DISTRIBUTION
CURRENT GALACTIC POPULATION MODELS Two main codes Trilegal (Girardi et al., 2005) Besancon (Robin et al., 2003) Inputs Structural parameters (scale heights, etc) Star formation histories Fe yields Outputs Number counts in (l,b) as a function of magnitude, color, and galactic component Distances, metallicities, ages and masses for each star Very helpful for testing target selection schemes
CURRENT GALACTIC POPULATION MODELS Advantages Makes predictions based on assumptions of Galactic structure and star formation history Analytic: minimal published predictions Semi-analytic & numerical: not detailed enough (yet!) Give number counts as well as a little chemical information Shows superposition of Galactic populations Covers whole Galaxy Disadvantages Not formed hierarchically Extremely limited chemical information Limited kinematic information
CHEMICAL EVOLUTION OF THE BULGE MERGING SUBCLUMPS Rahimi et al. 2010
OBSERVATIONAL SIGNALS CAN BE SUBTLE
CLOSING THOUGHTS Very excited by this workshop APOGEE represents a unique data set current models are not good enough Explaining the disk and bulge is very demanding Mass coverage Metallicity coverage (Z can be complicated!) But have many elements to compare Successful interpretation of the data will inform nucleosynthesis yields, star formation and accretion histories, and mixing Cross-calibration between surveys will be important; we are working on it.
2MASS EXAMPLE, L=90, B=10 Left: dereddened 2MASS data Middle: TRILEGAL simulation metal-poor giants (green) metal-rich giants (red) Right: Luminosities of stars from TRILEGAL simulation J-K=0.5 cut: good for getting metal-poor giants. J-K=0.7 cut: good at 24