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H-band multi-object spectroscopy around the Galaxy

H-band multi-object spectroscopy around the Galaxy. APOGEE. Carlos Allende Prieto (IAC) and the APOGEE Team. APOGEE. A high-resolution (R~30,000) high-S/N H-band spectroscopic survey of 100,000 stars in the Galaxy Why high-resolution? Why in the H-band? Why now?. Rationale.

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H-band multi-object spectroscopy around the Galaxy

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  1. H-band multi-objectspectroscopy around the Galaxy APOGEE Carlos Allende Prieto (IAC) and the APOGEE Team Science with the William Herschel Telescope 2010-2022

  2. APOGEE • A high-resolution (R~30,000) high-S/N H-band spectroscopic survey of 100,000 stars in the Galaxy • Why high-resolution? Why in the H-band? Why now? Science with the William Herschel Telescope 2010-2022

  3. Rationale • Red giants/red clump have strong NIR flux. Complete point source sky catalogue to H ~ 13.5 available from 2MASS • AH / AV = 0.17 (x 100 in flux at AV ~6) • Access to dust-obscured galaxy • Velocities to <1 km/s accuracy and precision abundances (15 elements) for giants across the Galaxy • Low atmospheric extinction makes bulge declinations accessible from North (though over smaller field) • Avoids thermal background problems of even longer  Science with the William Herschel Telescope 2010-2022

  4. APOGEE Science Case • In the context of Galaxy structure and evolution: sampling the distribution functions (x, v, Z) of the Milky Way avoiding the biases of working at visible wavelengths • In a broader context: does the Milky Way fit in a -CDM universe? Science with the William Herschel Telescope 2010-2022

  5. Terra incognita • Local thin disk well studied (Geneva-Copenhagen, S4N, Fuhrmann papers …) • Local and more distant halo well studied (SDSS) • Local thick-disk well-studied (just recently) • Not the case for the bulge (only Baade’s window explored) or distant parts of the Galactic disk Science with the William Herschel Telescope 2010-2022

  6. Specific objectives • Disk/Rotation Curve Surveys of stellar disk dynamics outside solar vicinity typically <~100 stars HI tangent point analyses assume circular rotation insensitive to non-axisymmetric effects (e.g., arms) and inoperable outside solar circle [V(>Rsun) poorly known]s I Gradients/lack of gradients in the thin/thick disks o Gas/stars in the spiral arms • Galactic Bar • Little current data, but possibly wide-ranging influence. Radial motions affect gas-mixing, metallicity gradients • Bulge Poorly known. Connection of velocities and chemistry provide s strong constraints on inflow of material into bulgear • Halo • Internal dynamics of substructure. Inner/outer halo dichotomy Science with the William Herschel Telescope 2010-2022

  7. What makes APOGEE’s spectrograph unique? • We know: Phoenix (KPNO 2.1m,4.1m, CTIO 4m, Gemini South), NIRSPEC (Keck), CRIRES (VLT) • We heard of NAHUAL (GTC), CARMENES (3.5m CAHA) R range detector Phoenix 50,000-80,000 1-5 m 0.5x1 K CRIRES <100,000 0.95-5.2 4x0.5x1K NIRSPEC 25,000 (2,000) 0.95-5.5 1x1 K Science with the William Herschel Telescope 2010-2022

  8. What makes APOGEE’s spectrograph unique? • Focused in the H band • Larger detectors • Grating (VPH vs. echelle): spectral coverage, efficiency • Multi-object (300 fibers) APOGEE 30,000 1.5-1.7 3x2x2 K Phoenix 50,000-80,000 1-5 0.5x1 K CRIRES <100,000 0.95-5.2 4x0.5x1K NIRSPEC 25,000 (2,000) 0.95-5.5 1x1 K Science with the William Herschel Telescope 2010-2022

  9. Hardware Overview Fold 2 (dichroic) Slithead (fiber “launch”) Fiber Racetrack Fibers in & LN-2 autofill Fold 1 VPH grating Collimator Camera Detector Assembly (mounts to Camera) Science with the William Herschel Telescope 2010-2022

  10. Hardware overview(Univ. of Virginia) • Fibers (high-transmission low frd): 40 m H-band optimized (65% throughput). Prototypes near top expectations in hand • Design includes a dichroic (cutting out thermal IR) Thanks to Fred Hearty for passing all the info! Science with the William Herschel Telescope 2010-2022

  11. Collimator Science with the William Herschel Telescope 2010-2022

  12. VPH • Size matters. Design calls for a 50x30 cm grating! • 3 recorded panels on a single gelatin substrate, sandwiched by two 2.5-cm layers. Several prototypes have demonstrated feasibility (should be done in April) Science with the William Herschel Telescope 2010-2022

  13. Volume Phase Holographic (VPH) Grating Science with the William Herschel Telescope 2010-2022

  14. Camera • All lenses built and coated assembly to begin in two weeks • 3 Teledyne 2048x2048 detectors (same as for JWST) QE~85% (dithering capabilities!) Science with the William Herschel Telescope 2010-2022

  15. Camera Science with the William Herschel Telescope 2010-2022

  16. Camera Science with the William Herschel Telescope 2010-2022

  17. Cryostat • All spectrograph cooled to 80 K in vacuum • No entrance window • Cryostat is 2.5x1.5x1.5m • Vibration isolated with common commercial solutions (>99% removed at >10 Hz) • Active thermal control (~1e-3 K) • Multiple calib. Sources (ThAr, U, laser comb) • Cryostat had 1st vacuum test, ready for 1st cold test. Delivery should happen in April Science with the William Herschel Telescope 2010-2022

  18. Science with the William Herschel Telescope 2010-2022

  19. Science with the William Herschel Telescope 2010-2022

  20. Science with the William Herschel Telescope 2010-2022

  21. Deliveries • A rich window sampling 15+ Elements (including C,N,O) • R~30,000 provides <<1 km/s velocity errors (probably much much smaller, but stellar jitter) • Fully automated reduction + analysis pipeline • 300 fibers on, 1e5 stars using bright time 3 yrs on ARC 2.5m Science with the William Herschel Telescope 2010-2022

  22. WHT • An APOGEE-like spectrograph on WHT would be a different instrument: smaller field, different science (e.g. clusters, extra-galactic red giants, integrated extragalactic globular clusters) • APOGEE, the spectrograph, costs is estimated at ~ 7 M$ (but much cheaper to repeat!) • Concept fully proven • Pipeline/acquis. Software can be recycled • IAC is negotiating full participation in SDSS-III (i.e. in APOGEE) Science with the William Herschel Telescope 2010-2022

  23. Another interesting example …VIRUS on the HET Science with the William Herschel Telescope 2010-2022

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