H-band multi-object spectroscopy around the Galaxy

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H-band multi-objectspectroscopy around the
Galaxy
APOGEE

• Carlos Allende Prieto (IAC)
• and the APOGEE Team

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APOGEE

• A high-resolution (R30,000) high-S/N
• H-band spectroscopic survey of 100,000 stars
  in the Galaxy
• Why high-resolution? Why in the H-band? Why now?

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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 lt1 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 ?

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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?

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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 Baades window
  explored) or distant parts of the Galactic disk

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Specific objectives

• Disk/Rotation Curve
• Surveys of stellar disk dynamics outside solar
  vicinity typically lt100 stars
• HI tangent point analyses assume circular
  rotation
• insensitive to non-axisymmetric effects (e.g.,
  arms) and
• inoperable outside solar circle V(gtRsun) poorly
  knowns 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

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What makes APOGEEs 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 lt100,000 0.95-5.2 4x0.5x1K
• NIRSPEC 25,000 (2,000) 0.95-5.5 1x1 K

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What makes APOGEEs 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 lt100,000 0.95-5.2 4x0.5x1K
• NIRSPEC 25,000 (2,000) 0.95-5.5 1x1 K

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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)
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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!
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Collimator
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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)

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Volume Phase Holographic (VPH) Grating
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Camera

• All lenses
• built and coated
• assembly to
• begin in two
• weeks
• 3 Teledyne
• 2048x2048
• detectors
• (same as for JWST)
• QE85 (dithering capabilities!)

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Camera
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Camera
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Cryostat

• All spectrograph cooled to 80 K in vacuum
• No entrance window
• Cryostat is 2.5x1.5x1.5m
• Vibration isolated with common commercial
  solutions (gt99 removed at gt10 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

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Deliveries

• A rich window
• sampling 15
• Elements
• (including C,N,O)
• R30,000 provides
• ltlt1 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

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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)

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Another interesting example VIRUS on the HET